Rejuvenation and Restoration of Surface Water Quality Amid COVID-19 Lockdown: A Comprehensive Review in Indian Context

Gunjan Arora; Tanishka Sharma; Kirti Kashyap Taijas; Parul Pant; Chetna Gupta; R. K. Sharma

doi:10.4491/eer.2022.144

Environ Eng Res > Volume 28(3); 2023 > Article

Arora, Sharma, Taijas, Pant, Gupta, and Sharma: Rejuvenation and Restoration of Surface Water Quality Amid COVID-19 Lockdown: A Comprehensive Review in Indian Context

Review

Environmental Engineering Research 2023; 28(3): 220144.

Published online: May 30, 2022

DOI: https://doi.org/10.4491/eer.2022.144

Rejuvenation and Restoration of Surface Water Quality Amid COVID-19 Lockdown: A Comprehensive Review in Indian Context

Gunjan Arora^1,², Tanishka Sharma², Kirti Kashyap Taijas², Parul Pant^2,^†, Chetna Gupta^2,^†, R. K. Sharma^1,^†

¹Green Chemistry Network Centre, Department of Chemistry, University of Delhi, Delhi-110007, India

²Department of Chemistry, Hansraj College, University of Delhi, Delhi-110007, India

^†Corresponding author: E-mail: rksharmagreenchem@hotmail.com, Tel: +91 011-27666250, Fax:, ORCID: 0000-0003-4281-876X

Received March 30, 2022 Revised May 25, 2022 Accepted May 29, 2022

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Rivers are our country’s lifeline; however, we have done enough destruction to them which leads to deterioration in water quality. Fortunately, COVID-19 lockdown has brought new life to nature. This encouraged us to outline present review article which discusses pilot impacts of lockdown on six Indian rivers. Few rivers including Ganga showed major improvement at few sites in the assessed parameters such as pH, BOD, DO, FC, etc. The Ganga water at Haridwar and Rishikesh was investigated ‘fit for drinking’ (Class A) while at Kanpur was found fit for ‘outdoor bathing’ (Class B). These improvements can be attributed to strict restriction on human activities during lockdown as there were no or minimum industrial discharge, tourism activities, mass bathing and commercial events near rivers. However, after upliftment of lockdown, these activities will return to their previous state and most likely pollutants will eventually reappear in the water bodies. So, in this review we have reviewed government’s existing water pollution control schemes, analysed their limitations and recommended several scopes for improvement. Further research directions in this area have also been highlighted. We believe that plans and actions described in the article, if implemented, will lead to fruitful outcomes in managing water resources.

Keywords: COVID-19 lockdown, Future plans and strategies, Indian riverine system, River rejuvenation

Graphical Abstract

Keywords: COVID-19 lockdown, Future plans and strategies, Indian riverine system, River rejuvenation

1. Introduction

December 2019, Hubei province of China experienced an outburst of an unprecedented disease named as Corona Virus Disease 2019 (COVID-19) [1]. The contagious COVID-19 disease was declared as a global pandemic on 11^th February 2020 and has affected millions of the people worldwide [1, 2]. To stop this pandemic, lockdown was viewed as the immediate measure. In view of this, a nationwide lockdown was imposed in India on 24^th March, 2020 with an enforcement of various rules and regulations [3]. Lockdown seriously disrupted the life of the people by posing many prolonged adverse socio-economic impacts. During these times economic activities came to a standstill, people suffered from loss of livelihoods, production and demand systems were collapsed and healthcare systems were overburdened [4–8]. Therefore, scientists across the world attempted to study effect of these unprecedented restrictions on human activities on broad fields such as psychology, socioeconomics, agriculture, environment, and tourism to name a few [9–13]. Interestingly, the imposition of the lockdown turned out to be inoculation to the environment resulting in overall improvements in lithosphere, atmosphere, and hydrosphere [14–18].

Water pollution is a common phenomenon of both developed and developing countries where untreated domestic and industrial wastes are dumped directly into water bodies [19–21]. However, during lockdown period, due to the complete shutdown of industries, socio-cultural activities, tourism and all non-essential works and restrictions imposed on the transportation systems, a huge reduction in the greenhouse gas emissions and discharge of domestic, industrial, and other pollutants into the environment have been observed globally. In this regard, water quality improvements have been studied and documented by various researchers from different countries [22–26]. Various parameters were analysed such as pH, DO, BOD, TDS, FC, metal ion concentration, level of inorganic and organic pollutants, plastic pollution, colour, odour, transparency, turbidity, and effect of aquatic life. Majority of the studies reported positive impression of lockdown on physical, chemical, and biological health of hydrosphere.

All these studies encouraged us to design the present review article where we aim to summarize the available scientific literature and analyse the primary impacts of COVID-19 lockdown on the Indian riverine system. We have analysed essential parameters (where data available) for six different rivers of the India and compared the trends before and during the lockdown period. Another motive of the article is to interpret learnings from the lockdown and recommend certain modifications in the existing river revival schemes. For this, we have first reviewed government’s current water pollution control and river revival schemes and their limitations. Further highlights are directed towards the probable future plans and actions that can be implemented to achieve fruitful outcomes in managing the water resources. Although a few literature reviews are available with similar aims to study effect of pandemic on natural resources on a global scale [27–30], we on the other hand have managed to diagnose and highlight the effects in heavily populated territories, where there is a lack of advanced wastewater treatment plants and availability of adequate quality water is a challenging and urgent need. We endorse that such countries must prioritize implementation of effective wastewater treatment schemes in their existing water policies.

1.1. Indian Riverine System: An Overview

India accounts for nearly 4% of the world’s water resources, including various forms of surface water [31]. Among all, rivers hold crucial significance in the country and are used for various purposes such as drinking, irrigation of crops, generation of electricity and many more [32]. The Indian rivers are divided into Himalayan and Peninsular rivers on the basis of their origin. Ganga, Indus, and Brahmaputra riverine systems form a large river basin constituting the Himalayan rivers and flows through the Northern plains of India. Mahanadi, Godavari, Krishna, Cauvery are the major rivers flowing across Peninsular India and are characterised by their seasonal flow. These rivers and their various tributaries comprise India’s river system [33]. Various important civilizations and cities like Delhi, Varanasi and Ahmedabad are situated on the banks of the river. Thus, rivers have an enormously important role on the economy and lives of the people of India. Nevertheless, the overexploitation and dumping of the largely untreated industrial, municipal and domestic effluents into these water bodies results in the water pollution which ultimately mutating our precious resources into a trash [34]. The factors like population outburst, deforestation, technological advancements, unplanned urbanization, agricultural developments, and industrial upliftment have also contributed immensely towards the increasing water pollution. A wide range of chemicals, pathogens and other toxic substances have been found in the waterbodies which accounts for the alterations in the physical, chemical, and biological characteristics of water causing harmful effects on human and aquatic life [35–37].

2. Major Pollutants in Indian Rivers and Their Adverse Effects

Access to clean and safe water has always been a major concern for mankind. With the ever-growing population, expanding industries and expeditious urbanization, toxic and hazardous waste materials are continuously being dumped into the water bodies. Amongst all, heavy metals (like lead, zinc, copper, chromium, cadmium, nickel and arsenic) constitute a major class of contaminants as they have long-term persistence in water bodies and leads to severe environmental pollution [38]. Heavy metals have relatively high density and are toxic and hazardous for life if present above a permissible limit. Harmful substances and chemicals used in fertilizers, insecticides and pesticides may leach in water bodies [39, 40]. Flawed mining processes, discharge of industrial effluents containing metallic solutions, dumping of solid waste and chemicals such as metal-based biocides used in agricultural processes are some of the major causes of heavy metal accumulation in rivers. Industrial waste is another dominant class of contaminants that cause critical environmental deterioration. Industries related to dyeing, tanning, printing, battery manufacturing units, etc. largely operate alongside the rivers and discharge their effluent directly into the mainstream, thus polluting them heavily and affecting the water quality (Table S1 describes the current limit values imposed by the legislation on industrial discharges into rivers). Different types of chemicals which are responsible for the increased water pollution in Indian water bodies and their rate of production per year have been depicted in Fig. 1.

These chemicals once landed up into the water possess severely negative effects on the living beings and on the environment. Unfortunately, water pollution leads to more than 14,000 deaths per day, high rate of infant mortality, degradation in biodiversity, outbreak of chronic diseases and many more [41]. Table 1 summarizes the major pollutants found in the Indian rivers, their sources, and toxic effects on living species.

3. Government’s Schemes to Combat Water Pollution

Considering the continually deteriorating quality of our water resources and the adverse effects it poses on all forms of life, government of India launched various schemes and programs to combat water pollution. In this regard, the Water (Prevention and Control of Pollution) act of 1974 was the very first initiative of the government towards curbing water pollution. The purpose of this act was to prevent and control water pollution, as well as to maintain and restore the wholesomeness of water [53]. Central/state pollution control board (CPCB/SPCB) was established under this act as a regulating body for pollution control. The CPCB is the apex body in field of water quality management. The CPCB in collaboration with SPCBs has developed a concept of “designated best use”, based on which it has graded the water bodies on the basis of their pH, dissolved oxygen (DO), biological oxygen demand (BOD), conductivity, free ammonia and total coliform matter. This classification or gradation of water bodies not only assists water quality managers and planners in setting water quality targets but also in identifying needs and priorities for water quality restoration programs for India’s various water bodies. Many programs have been launched by the Government of India to clean the rivers. The first such plan was the Ganga Action Plan (GAP). The ambitious GAP was launched on January 14^th, 1986, to clean the Ganga river. According to ministry of environment and forest, 6788.78 crore Indian currency was released by Prime minister late Shri Rajiv Gandhi to clean Ganga [54]. Nevertheless, only 39% of its primary target of sewage treatment was met as indicated in an audit report by the comptroller and auditor general (CAG). The complete top-down bureaucratic exercise and lack of data on water usage and wastewater generation were the most important reasons for failure of GAP [55].

After the failure of GAP, the government in 2009 took a more comprehensive step. A basin-wide and multi-sectoral approach was taken, and National Ganga River Basin Authority (NGRBA) was constituted. The NGRBA is a planning, financing, monitoring and coordinating body of the centre and state government whose aim is to ensure effective pollution abetment and conservation of national rivers. The NGRBA received USD 1 billion loan sanctioned by the world bank in 2011. This body was dissolved in 2016 and was renamed as National Council for Rejuvenation, Protection and Management of River Ganga [56]. The parliamentary committee on Environment and Forests states that the reason for the failure of NGRBA were that the social aspects of pollution in the rivers were ignored and their catchment areas were encroached upon and diverted for construction and development activities [57].

After the dissolution of NGRBA, a new mission called “Namami Gange” was launched by the government of India with a budget of more than $3 billion [58]. The major objective of this project was to improve the quality of Ganges with continuous and unpolluted flow while maintaining its ecological and geological integrity. The project programmes were based on recommendations of Ganga River Basin Management Plan (GRBMP) and the main activities included were construction of bigger sewage treatment plants with increased capacity, riverfront development programmes, biodiversity conservation and afforestation along river banks, public awareness and industrial effluent monitoring [56]. The government has also implemented National River Conservation Plan (NRCP) for abetment of pollution in identified stretches of various rivers. The states have also prepared action plan for sewage management and restoration of river quality in aquatic sources [59]. The goal of the NRCP is to assess the water quality of the state’s rivers, that are the major water sources, through the implementation of pollution reduction projects. The highlights of NRCP include 77 towns and 34 rivers in 16 states. The sanctioned cost of detailed project report was Rs. 5870.54 crores. A fund of Rs. 2510.63 crores have been sanctioned by the government of India whereas the expenditure has been 3339.96 crores. The total pollution load tackled has been estimated as 2520.43 MLD [60]. On the similar note, various other plans were launched to rejuvenate major rivers of the country. For instance, the Yamuna Action Plan was launched in 1993, with successive phase II in 2001, was aimed at rejuvenating river Yamuna [61]. Strengths, achievements and weaknesses of different government schemes to clean major rivers of India have been documented in table 2. Apart from these major undertakings by government, the CPCB has adopted various methodologies to curb water pollution (Fig. S1).

Thus, the government is taking numerous steps towards cleaning national rivers (Fig. 2), however despite these efforts and investing huge amount of budget, the quality of our water resources is still unacceptable. The CAG report of 2017 stated that the ‘Namami Gange’ mission does not have a river basin management plan even after NGBRA notifications. The coliform level in Ganga was found to be 3343 times higher than prescribed limit of 2016–17. Mercury metal is still being under-reported [56]. Disregarding the guidelines, people are still bathing and washing in rivers, idols are still being immersed, no proper cremation ghats are present across the rivers and untreated water is still being discharged into water bodies. According to WHO report of 1992, only 209 towns out of 3119 towns have partial sewage treatment facility whereas only 8 have full water treatment facility [53].

A new water policy and action plan has been prepared which suggests new policies that India should adopt to curb water crisis and pollution. The action programme of the plan states that community partnership and privatization, change in institutional structure, watershed project implementation, legal framework changes, financial assistance and modernization will help in outnumbering the shortcomings of previous programmes.

4. Wastewater Remediation Technologies

Besides Government’s water policies and schemes, many wastewater remediation technologies have also been developed and applied to deal with a variety of contaminants present in the water bodies. These technologies include various physical, chemical, and biological methods for wastewater remediation where a variety of materials have been used (Fig. S2) [62–73]. Further, various thermal and electro-chemical technologies are available that are used to treat saline wastewater [74–76]. Among all, adsorption is one of the best available technologies as it is convenient, has broad applicability, high efficiency, good selectivity, and cost effectiveness [77–81]. On this perspective, our research group is working to develop various efficient and reusable materials as adsorbents to selectively remove contaminants [82–88] and as catalysts that have remarkable efficiency for degrading toxic water pollutants [89–91]. Membrane processing, ion exchange, electrochemical precipitation, photo-chemical treatment, solvent extraction, adsorption and chemical- and biological-degradation are some of the other most employed technologies for this purpose [92–103]. However, majority of these techniques work effectively under certain operational conditions and can be futile in other circumstances. Table S2 summarizes merits and demerits of some of the mentioned techniques [63].

5. Methodology

This study was conducted by reviewing published literatures including research articles, reports from CPCB, SPCB and other government and non-government organizations, case studies, scientific opinions, and websites. Literature was searched by using different electronic means majorly Google Scholar, Research Gate, Science Direct and PubMed. The following terms were used while searching: ‘COVID-19 pandemic’, ‘lockdown’, ‘water’, ‘positive impact’, ‘environment’, ‘Indian rivers’, ‘water quality’, ‘aquatic life’, etc. Further we restricted our search to articles published in English language.

6. COVID-19 Lockdown and Improvement in Water Quality

A significant improvement has been seen in the quality of water within 10 days from imposement of the lockdown, which the various schemes of the government with crores of rupees pumped in, were unable to do for past few years. Referring to Fig. 1, it is clear from the trends of the graph that the amount of chemical production increased up-till 2019 but the lockdown imposed in view of COVID-19 pandemic dented the production of these chemicals, thus reducing the pollutants and hence the pollution in Indian rivers. Moreover, lockdown offered an opportunity to assess the water quality of some of the major rivers in India and compare it with pre-lockdown period [104]. Some of the rivers that improved during the lockdown period are discussed below.

6.1. River Ganga

The river Ganga, being one of the largest rivers on the Earth, is known to be the lifeline of millions of Indians. The national river flows over 29 cities, 97 towns and thousands of villages and thereby is severely polluted with industrial effluents and domestic sewages (Fig. S3). The nationwide lockdown appeared to be a gift to Ganga as there was an improvement seen in the quality of water within 10 days which the various schemes of the government with crores of rupees pumped in, were unable to do for past few years. Since the river was extensively polluted, COVID-19 lockdown served as an opportunity for CPCB and SPCBs to study the water quality of the river system before and during the lockdown period [105]. It is reported that water collected from 42 out of 65 monitored locations (64.6%) before lockdown and 25 out of 54 monitored locations (46.3%) during lockdown is categorized well within the desirable limits of primary water quality criteria for outdoor bathing. As per the report of Uttarakhand pollution control board, the Ganga water at Haridwar and Rishikesh was investigated ‘fit for drinking’ (Class A) giving a positive sign towards restoration of the river as the levels of DO, BOD and TC were within prescribed water quality criteria. Following this, the water quality observed between Haridwar, and Kanpur was found fit for outdoor bathing (Class B). A huge withdrawal of water was avoided since there was a complete halt on the water-intensive agriculture. Excessive rainfall during the lockdown period further improved the river flow leading to dilution of pollutants in the river. This resulted in an increase in the concentration of DO (above 5 mg L⁻¹) at all the locations [105]. Overall moderate improvement in water quality of river Ganga was noticed with respect to the parameters i.e., DO, BOD and FC.

The higher rainfall also attributed to the increase in the turbidity and suspended solids in the river after the lockdown. The assessment of BOD of Ganga River before and during the lockdown makes it evident that there was a major decrease in BOD during the lockdown period at most of the stations. At the same time, a marginal decrease in chemical oxygen demand (COD) values have been noted due to complete restrictions on industrial activities. The lockdown also ensured the reduction in nitrate concentration and the values of ammoniacal nitrogen were also seen less than the prescribed criteria of 1.2 mg L⁻¹ limit along with an improvement in bacterial quality of the river [105].

According to the of data of CPCB, out of 36 monitoring stations, the water quality at 27 points was found suitable for bathing (Class B) and 9 points suitable for propagation of wildlife and fisheries (Class C). The data also shows an increase in DO values of the river at most of the locations. Overall analysis on river Ganga before and during lockdown period is depicted in Fig. S4.

6.2. River Yamuna

Yamuna, the largest tributary of the river Ganga is known to be one of the most polluted rivers in the world. The 2% of Yamuna’s total length flows through National Capital Territory (NCT) of Delhi and receives 79% of its total pollution in this stretch of about 48 km making it the worst affected stretch of the entire river (Fig. S5). A study was conducted by Patel et al. to ascertain the impact of restricted anthropogenic activities on the water quality and a significant improvement in the water quality index (WQI) was recorded out of 9 monitoring stations [106]. A notable reduction in the concentration of polluting parameters, despite not receiving a substantial amount of rainfall, was also observed during the lockdown phase between 6^th April to 14^th April 2020 when compared to the pre-lockdown phase [106]. Whereas in some areas of NCT, the Yamuna water quality did not meet the prescribed limit of WQI values (except Palla and Surghat), even after 3 weeks of complete lockdown which highlights the concern over the deterioration in the water quality of Yamuna. The mean concentrations of BOD and COD (considering all monitoring stations) had changed by −42.83% (net reduction of 11.82 mg L⁻¹) and −39.25% (net reduction of 32.06 mg L⁻¹), respectively when compared with the previous year’s reduction amounts of 19.78% and 10.45%, respectively [106]. Despite all this, the water quality parameters in some monitoring stations like Khajori Paltoon did not even meet the Class B and Class C standards.

The lockdown has proven to be boon for the river and a finding by Delhi Pollution Control Committee (DPCC) showed that the river Yamuna in Delhi has cleaned by around 33%. The analysis of monitoring stations at Delhi revealed that:

Four critical parameters during pre-lockdown period were pH (7.2–8.7), DO (17.1mg/L), BOD (7.9–78 mg/L) and FC (1300–920000 MPN/100mL) at the 05 monitored locations while during lockdown these parameters were found to be pH (7.1–7.8), DO (1.2–8.3 mg/L) and BOD (2–6.1 mg/L).
Before lockdown, BOD at all monitored locations was not conforming to the limits described for primary water quality for outdoor bathing while during lockdown BOD at 1 monitoring station was complying within the limits.
Overall decreasing trend was noted for DO (51.46%) at 01 location and BOD (74.70% – 90.20%) at 03 monitoring locations.

6.3. River Godavari

Godavari is the second longest river in India which traverses via Telangana, Andhra Pradesh, and Chhattisgarh (Fig. S6). CPCB in association with Maharashtra Pollution Control Board (MPCB), Telangana State Pollution Control Board (TSPCB), Andhra Pradesh Pollution Control Board (APPCB) monitored the water quality to access the impact of lockdown on the river water quality. It was revealed that 29 out of 37 monitoring locations were in accordance with the water quality criteria for outdoor bathing [104]. A maximum reduction in BOD levels from 6.8 to 6.2 mg L⁻¹ and FC levels from 70 to 47 MPN/100mL were seen at Tapovan. An increasing trend in the levels of DO at 19 locations, BOD at 5 locations and FC at 5 locations were also observed.

Overall assessment of the data obtained from different SPCBs revealed that:

Maharashtra: It was observed that DO was increased at 9 locations (1.5% – 61.3%), decreased at 3 locations (1.5–3.1%) while 2 locations showed no variation. Similarly, BOD (7.7–27.3 %) and FC (28.6 %) was increased at 3 and 1 locations, respectively. While decreasing trend in BOD (5.9–29.5 %) and FC (15–45.5 %) was recorded at 10 and 4 locations, respectively.
Telangana: It was observed that DO was increased at 9 locations (4.2–46.3%), decreased at 3 locations (1.4–28.6%) while 4 locations showed no variation. Similarly, BOD (14.3–33.3%) and FC (46.7–100%) was increased at 2 and 3 locations, respectively. While decreasing trend in BOD (3.3–30%) was recorded at 5 locations.
Andhra Pradesh: It was observed that DO was increased at 1 location (1.5%), decreased at 5 locations (1.5–26.2%) while 1 location showed no variation in DO. Similarly, BOD (5.6–57.1%) and FC (33.3%) was increased at 3 and 1 locations, respectively. While decreasing trend in BOD (13.3–40.9%) and FC (26.7–63.6%) was recorded at 4 and 5 locations, respectively.

Thus, when compared with pre-lockdown period, it was evident that lockdown emerged as a tool for cleaning the river [104].

6.4. River Gomti

River Gomti, a tributary of river Ganga, enters Lucknow after a journey of 190 km which flows in the middle of city and is employed for drinking and other domestic purposes at many locations (Fig. S7). A study was conducted by Khan et al. to evaluate the impact of COVID-19 lockdown on the heavy metal pollution status on the river Gomti at Lucknow city [107]. 30 samples from well-mixed segments (three at each sampling station) were collected from the river, across a total stretch of nearly 61 km in June 2020 to analyse the heavy metal levels within the water samples. The assessment of pollution levels and influence of heavy metals in water quality is classified using an index called heavy metal pollution indices (HPI). A considerable improvement in HPI was witnessed at all sites, with an overall average improvement of 19.15% in June 2020 when compared with pre-lockdown period signifying the impact of closure of industrial enterprises on the river water. The average concentration of As, Cd, Pb, Mn, and Cr metal at all sites showed a reduction of approximately 29%, 15.13%, 11.21%, 9.62%, and 16.37%, respectively which signifies the effectiveness of control measures (Fig. 3) [107].

The maximum improvement in the values of HPI was observed at site S1 (Chandrika Devi) with a drastic reduction of 32.2% due to the halt in agricultural activities. At the same time a decrease of 25.28%, 14.46, and 16.78% in the HPI values was observed at sites S2 (IIM Road), S3 (Harding Bridge), and S4 (Arti Sthal), respectively. Stations S8 (Dilkusha Bridge), S9 (Shahid Path) and S10 (Bharwara STP Discharge point-Gomti Confluence) situated at downstream locations also showed a notable improvement of ~21.2%, ~32%, and ~19.2 in individual HPI values, confirming the positive impact of the COVID-19 lockdown (Fig. S8) [107].

6.5. River Damodar

Damodar, a river of total length 563 Km, flows across the states of Jharkhand and West Bengal (Fig. S9). There are many industries established in both sides of the river which highlights the importance to evaluate the changes in the water quality during the lockdown period. A study was conducted by Chakraborty et al. in which water samples from 11 discharge sites of industries were collected before (December 2019) and during the lockdown period (July 2020) [108]. The significant change in the pH level of the river from 7.04–8.21 before lockdown to 6.12–7.72 was observed during the lockdown period which is directly related to the lesser disposal of effluents from the industries. Lower mixing of waste materials in the river resulted in the decrease in the TDS from 665.6 to 806.4 mg L⁻¹ in pre-lockdown period to 480 to 563.2 mg L⁻¹ during lockdown period [108]. Since TDS and EC are linked to each other, decrease in TDS decreases the EC which ranged from 1040 to 1260 μS cm⁻¹ in pre-lockdown period and from 750 to 880 μS cm⁻¹ during lockdown period which was lower than the standard limit according to WHO (2011).

The mean cation concentration of major cations (Ca²⁺, Na⁺, Mg²⁺, K⁺) were lowered down to their standard limit set by WHO (2011) as compared to their high concentration before the lockdown session. Similar results were seen in case of anions (SO₄²⁻, Cl⁻, NO₃⁻ and F⁻) which is allocated to the fact that no mixing of industrial toxic elements took place during the lockdown.

6.6. River Bhogavati

Bhogavati River, which originates near Osmanabad city of Maharashtra (Fig. S10), was studied at village Balinga in Kolhapur district of Maharashtra after three weeks of the enforcement of nationwide lockdown to compare the physico-chemical parameters of the water quality before and after the lockdown. It was found that the water quality parameters like pH, TDS, hardness, EC, etc. showed betterment in the quality of water during lockdown (Fig. 4) [109].

Table 3 compares various water quality parameters recorded before and during the lockdown period for major rivers in India.

7. Impact of COVID-19 Lockdown on Aquatic Species

A wide variety of aquatic species including plants, animals and other small living organisms can be found in the water bodies. Increasing pollution of surface water and climate change poses some serious and threatening effects on the survival of these aquatic plants and animals. The lockdown not only boosted the physical health of water resources, it also contributed largely towards improving the biological health. Studies have ascertained that due to positive changes in water quality, aquatic life is flourishing in the rivers, especially the number of fishes has found to be increased when compared with pre-lockdown period. A news article by ‘Timestravel’, Kolkata published that Gangetic dolphin were located at Kolkata ghats after a good 30 years [117]. Moreover, a report published by ‘ActionAid Association’ states that “there has been increase in aquatic species in Mahanadi, Narmada, Ganga, Yamuna and Nagavali while there was large majority reported increase of aquatic life in Krishna (75%), Kaveri (70%), Gandak (75%), Godavari (80%) and Gomati (78%)” (Fig. 5) [118].

8. Analysis and Interpretation

8.1. Potential Reasons for Improvement in Water Quality

8.1.1. High rainfall during the period

The surplus rainfall during the lockdown was the result of simultaneous occurrence of higher number of western disturbances, which improved the self-cleansing properties of the rivers. India Meteorological Department, New Delhi observed that the Ganga basin experienced 60% increase in rainfall than normal from March 1 to May 6, 2020, leading to the dilution of pollutants in the river [105].

8.1.2. Reduction in the discharge of untreated water into natural sources

The COVID-19 lockdown ensured the reduction in discharge of untreated industrial wastewater from the tanneries to the rivers which majorly destroys the quality of the rivers. When these effluents get mixed with the domestic sewages, they badly affect the self-cleansing properties of the rivers. It was analysed that there was a total reduction of 1300 to 1340 MLD of toxic industrial effluents during the period [105].

8.1.3. Halt on activities such as tourism, bathing and cloth washing

Since there was complete restriction on activities such as tourism, fairs, bathing and washing clothes, which usually has a severe impact on the quality of river, the rivers did not experience any problems related to solid wastes and littering by the visitors [105].

8.1.4. Decline in electricity demand

According to the Power System Operation Corporation, in India, the daily demand for electricity got lowered by 32.2% to 1.91 billion units (kWh) on account of mandated nationwide lockdown which impacted the hydropower production during the period. This allowed more water to flow into the rivers and diluting various pollutants coming into the rivers [105].

8.2. Interpretation and Key Findings

In this work, we attempted to recognize the effect of restrictions imposed during COVID-19 lockdown on Indian river water quality. We collected and compiled research data from various published literature for six major rivers of India, namely Ganga, Yamuna, Godavari, Gomti, Damodar and Bhagovati to evaluate impact of lockdown on water quality. This investigation of water quality parameters for different rivers will help researchers to understand key steps that should be incorporated in the existing water management system to achieve long term benefits. Some of the key findings of the work are:

During lockdown, discharge of domestic and industrial effluents such as heavy metals, plastics, wastewater, crude oil, etc. have been reduced or stopped largely, therefore, decrease in pollution level was seen. Due to which not only chemical health but physical and biological health of rivers was improved.
Physical: Major improvements were seen in terms of cleanness, colour, transparency, and odour of water.
Chemical: Studies revealed that there has been significant improvement in water quality in terms of DO, BOD, COD, FC, TDS, pH, and other parameters. Moreover, the concentration of heavy metal pollutants has been reduced.
Biological: We analysed that there have been considerable changes in aquatic life too. It has been observed that the presence of aquatic species especially fishes have increased due to decrease in water pollution. There has been rise in aquatic species in various rivers including Ganga, Yamuna, Godavari, and Gomati. Even the Gangetic dolphin could be located at Kolkata ghats after a good 30 years.
Few studies also reported the increase in the presence of migratory birds around water bodies. 100% increase was seen around river Ganga and Yamuna while 80% was observed around Gomati River.
Reduction in the discharge of untreated water, decrease in human interferences, halt on activities such as tourism, bathing and cloth washing, decline in electricity demand and high rainfall during the period due to improved climatic conditions are described as potential reasons for improvement in water quality.
It is a matter of concern that how much pre-treatment is required for effluents prior to discharging it into rivers. Government needs to ensure that no effluent could enter river stream without proper treatment. Simply investing high budget projects will not help in cleaning rivers. Rather it requires strict punishments against industries discharging untreated waste into the water.
The findings indicates that nature has self-capacity of healing, cleansing, and maintaining its resources until human interferences are minimal.
With the resumption of industrial activities, tourism and other human interventions, the pollutants will eventually reappear in the water bodies therefore, it is essential to learn lessons from nature and inculcate them in future strategies on the priority basis.

9. Recommendations and Future Directions

India is presently undergoing a decrease in freshwater resources. Scarcity of water is an issue in many parts of the country. If the country’s water use efficiency does not improve, it may face drought conditions within the next couple of decades. Therefore, water management in India has been a concern whose amplitude has grown exponentially over the last 50 years attributed to a myriad of factors. Major river water management challenges in India can be broadly classified as a) water accessibility, variance and increasing withdrawals b) the ecosystem and quality c) project development d) water-sharing conflicts e) water oversight and organizations and f) challenges induced by urbanization and climate change [119]. To overcome these challenges, there is an urgent need for the modifications in water-related guidelines, strategies, and regulatory frameworks.

COVID-19 lockdown showed us that how the shutting down of industrial units, decrease in discharge of untreated industrial and municipal waste and halt on human activities (like tourism, bathing, cloth washing, etc.) in water bodies has led to significant improvements in river water quality and facilitated flourishing of new lives in polluted rivers. However, there is a considerable uncertainty about how long these improvements will sustain after the complete upliftment of restrictions which were imposed during the lockdown period. Most likely, with the resumption of industrial activities, tourism and other human interventions, the pollutants will eventually reappear in the water bodies. In this scenario, we strongly believe that the teachings from the lockdown will surely help in the better management of our resources, and these should be reflected in the future plans and models for the rejuvenation of water systems. Therefore, in this section, we have tried to highlight gaps in the existing water management plans and recognize the various key factors that should be considered in future strategies for better management. In our view, future strategies should focus on the following key areas:

Appropriate measures and policies must be adopted by CPCB to ensure adequate wastewater treatment. Before the discharge of sewage and different effluents into the water bodies, they must be treated and bring to the prescribed limits.
Emphasis should be given to provide affordable sanitation in urban areas to reduce introduction of human waste in the water bodies. Besides, awareness drives should be conducted among slum communities which will help in improving waste management, increasing health awareness, and improving sanitation facilities to reduce contamination of water bodies.
Adaptation of fully integrated river basin planning techniques over isolated wastewater treatment methods (one treatment plant per municipality) would prove to be more sustainable and resilient approach. Integrated approaches would allow for more effective expenditures by developing effluent regulations based on the specific circumstances of distinct water bodies.
From an Indian perspective, the integrated water resource management (IWRM) strategy is extremely relevant and beneficial. This plan is divided into three categories (water, land and livelihood management) and offers particular recommendations based on the vulnerabilities and livelihood opportunities in specific geographical locations. It also takes into account different geomorphological, hydrological, pedological, ecological, and sociocultural features.
Proper land management and water conservation policies should be implemented which will help in sustainably managing the fresh water resources and water table. This will help in dilution of pollutants in water bodies.
Green infrastructure can become a major opportunity as it offers a solution to many water woes. Vegetated rooftops, roadside planting, absorbent gardens and other such measures can cut down the pollutants reaching to rivers and lakes and will help in increasing the quality of rivers. Protection and creation of forest patches in catchment areas will also benefit in reducing pollution levels in the rivers.
To verify noncompliance with treatment of wastewater and discharge, strict quality regulation and enforcement are required. The SPCBs are not well equipped to handle it and hence a new system must be developed.
Strict implementation of rotatory lockdown must be executed near riversides. This would definitely improve water quality.

Sufficient financing is also required to make the necessary changes to the current system. Once funding is secured, resources should be directed toward repairing existing sewage treatment plants. The emphasis should be on ensuring that the treatment load meets the needs of the area, with room for the inevitable growth in population. Funding must be invested in the purchase of generators, which will allow treatment plants to operate during frequent power outages. To keep treatment malfunctions to a minimum, a task force of qualified scientists and engineers must collaborate to train more people on how to run and keep the current systems. This is a multifaceted problem with no simple solution; however, strategic action must be a top priority for the Government of India in aimed at improving the lives of the people who live along the river and the river ecology [120].

10. Opportunities for Future Research

Real-time monitoring of pollutant concentration in water and availability of proper waste disposal and treatment technologies also play a key role in restoration of water quality. Therefore, current state-of-art is to develop novel, cost-effective and efficient methods for wastewater remediation. Although a lot of treatment processes have been reported in the literature including adsorption, extraction, membrane filtration, ion exchange, chemical precipitation, bioremediation, thermal and electrochemical techniques, but still there are some demerits associated with them such as cost, efficiency, and large-scale implementation. In our view, these barriers can be overcome by integrating two or more techniques together in a synergistic means to produce better results. Therefore, more such hyphenated processes should be developed in near future and scaled to pilot level. Besides, development in sensitive and quick detection techniques for real-time pollution monitoring is much desirable. Smart sensors that are flexible, portable and are capable for simultaneous detection of different analytes could be an area to worth exploring in the near future.

11. Conclusions

In this article, we presented a snapshot of the primary impacts of COVID-19 lockdown on the water quality of densely populated territory, India. Data reviewed in the article suggest that there is overall marginal enhancement in water quality of river Yamuna and Godavari with respect to primary water quality criteria for outdoor. River Ganga showed improvements in DO and decline in BOD at few monitoring stations. The critical parameters for river Gomati were found to be in the range of pH (8.76), DO (6.35 mg/L) and BOD (3.50 mg/L) at different locations. Overall majority of the rivers showed improvements in DO, BOD, FC, and pH. The key factors leading to these improvements have been analysed in the review. Reduction in discharge of domestic and industrial effluents, decline in the consumption of electricity and improved climate conditions including changes in the rainfall patterns are major factors responsible for the enhancement of water quality. Based on the learnings from lockdown, we have presented various recommendations. In our view, the foremost priority must be to ensure that no industrial discharge could enter the river without proper treatment. Industries operating along-side rivers should be shut immediately and strict actions must be taken against polluting industries. Emphasis should also be given to provide affordable sanitation and green infrastructure. Protection and creation of forest patches in catchment areas will benefit in reducing pollution levels in the rivers. Besides, adaptation of IWRM strategy that takes into account different geomorphological and sociocultural features would be very beneficial. We also propose strict implementation of rotatory lockdown near riversides which would definitely improve the water quality. Besides, advanced wastewater and industrial effluent treatment plants and techniques should be introduced. We believe that the suggestions and future directions discussed in this review will help in revising the present strategies and will contribute towards the permanent restoration of water resources.

Supplementary Information

eer-2022-144-suppl.pdf

Notes

Conflict of Interest

The authors declare that they have no conflict of interest.

Author Contributions

G.A. (Senior Researcher-Lecturer) Conceptualization, original draft preparation, T.S. and K.K.T. (Undergraduate students) Original draft preparation, P.P. and C.G. (Assistant Professors) Organization, reviewing and editing and R.K.S. (Senior Professor) Reviewing and editing.

Funding sources

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

References

1. Coronavirus disease (COVID-19). World Health Organization. [Internet]. [cited 20 October 2021]. Available from: https://www.who.int/health-topics/coronavirus#tab=tab_1

2. Kumar D. Half a million COVID-19 cases in India: How we got to where we are. [Internet]. [cited 20 October 2021]. Available from: https://thewire.in/covid-19-india-timeline

3. The Economic Times. [Internet]. 2021. [cited 20 October 2021]. Available from: https://economictimes.indiatimes.com/news/india/one-year-since-a-complete-lockdown-was-announced-we-look-back-on-how-india-fought-covid/first-lockdown-announced/slideshow/81662838.cms?from=mdr

4. Joshi A, Bhaskar P, Gupta PK. Indian economy amid COVID-19 lockdown: A prespective. J. Pure Appl. Microbiol. 2020;14:957–961. https://doi.org/10.22207/JPAM.14.SPL1.33

5. Gurumurthy K, Priya AJ, Don KR. Effect of Lockdown on Indian Economy. Annals of RSCB [Internet]. 2021. [cited 20 October 2021]. Available from: https://www.annalsofrscb.ro/index.php/journal/article/view/2123

6. Abiad A, Arao RM, Dagli S, et al. The economic impact of the COVID-19 outbreak on developing Asia. Asian Development Bank. [Internet]. 2020. [cited 20 October 2021]. Available from: https://www.adb.org/publications/economic-impact-covid19-developing-asia

7. Kirti KT. The Economic Transcript. What Should be India’s economic pathway? [Internet]. 2020. [cited on 20 October 2021]. Available from: https://tetofficial.com/economic-pathway/

8. Kirti KT. The Economic Transcript. Financial Emergency [Internet]. 2020. [cited on 20 October 2021]. Available from: https://tetofficial.com/financial-emergency/

9. Bakar NA, Rosbi S. Effect of Coronavirus disease (COVID-19) to tourism industry. Int. J. Adv. Eng. Res. Sci. 2020;7:189–193. https://dx.doi.org/10.22161/ijaers.74.23

10. Lenart-Boroń AM, Boroń PM, Prajsnar JA, et al. COVID-19 lockdown shows how much natural mountain regions are affected by heavy tourism. Sci. Total Environ. 2022;806:151355. https://doi.org/10.1016/j.scitotenv.2021.151355

11. Hamadani JD, Hasan MI, Baldi AJ, et al. Immediate impact of stay-at-home orders to control COVID-19 transmission on socioeconomic conditions, food insecurity, mental health, and intimate partner violence in Bangladeshi women and their families: an interrupted time series. The Lancet Glob. Health. 2020;8:e1380–e1389. https://doi.org/10.1016/S2214-109X(20)30366-1

12. Thakur K, Kumar N, Sharma N. Effect of the pandemic and lockdown on mental health of children. Indian J. Pediatr. 2020;87:552. https://doi.org/10.1007/s12098-020-03308-w

13. Pulighe G, Lupia F. Food first: COVID-19 outbreak and cities lockdown a booster for a wider vision on urban agriculture. Sustainability. 2020;12:5012. https://doi.org/10.3390/su12125012

14. Karnan C, Sandhya SV, Gauns M, Pratihary A. Impact of lockdown on the environmental quality along the Indian coast and a tropical estuary. Cont. Shelf Res. 2021;15:104511. https://doi.org/10.1016/j.csr.2021.104511

15. Lokhandwala S, Gautam P. Indirect impact of COVID-19 on environment: A brief study in Indian context. Environ. Res. 2020;188:109807. https://doi.org/10.1016/j.envres.2020.109807

16. Kour G, Kothari R, Dhar S, Pathania D, Tyagi VV. Impact assessment on water quality in the polluted stretch using a cluster analysis during pre-and COVID-19 lockdown of Tawi river basin, Jammu, North India: an environment resiliency. Energy Ecol. Environ. 2021;29:1–2. https://doi.org/10.1007/s40974-021-00215-4

17. Chakraborty B, Bera B, Adhikary PP, et al. Positive effects of COVID-19 lockdown on river water quality: evidence from River Damodar, India. Sci. Rep. 2021;11:1–6. https://doi.org/10.1038/s41598-021-99689-9

18. Somani M, Srivastava AN, Gummadivalli SK, Sharma A. Indirect implications of COVID-19 towards sustainable environment: an investigation in Indian context. Bioresour. Technol. Rep. 2020;11:100491. https://doi.org/10.1016/j.biteb.2020.100491

19. Jung SP, Kim YJ, Kang H. Denitrification rates and their controlling factors in streams of the Han River Basin with different land-use patterns. Pedosphere. 2014;24:516–528. https://doi.org/10.1016/S1002-0160(14)60038-2

20. Çadraku HS. Groundwater quality assessment for irrigation: case study in the Blinaja river basin, Kosovo. Civ. Eng. J. 2021;7:1515–1528. http://dx.doi.org/10.28991/cej-2021-03091740

21. Guiamel IA, Lee HS. Watershed modelling of the Mindanao River Basin in the Philippines using the SWAT for water resource management. Civ. Eng. J. 2020;6:626–648. http://dx.doi.org/10.28991/cej-2020-03091496

22. Xu H, Xu G, Wen X, Hu X, Wang Y. Lockdown effects on total suspended solids concentrations in the Lower Min River (China) during COVID-19 using time-series remote sensing images. Int J. Appl. Earth Obs. Geoinf. 2021;98:102301. https://doi.org/10.1016/j.jag.2021.102301

23. Sarkar S, Roy A, Bhattacharjee S, Shit PK, Bera B. Effects of COVID-19 lockdown and unlock on health of Bhutan-India-Bangladesh trans-boundary rivers. J. Hazard. Mater. Adv. 2021;4:100030. https://doi.org/10.1016/j.hazadv.2021.100030

24. Hamidi SA, Abbasi B, Hamidi H. Investigation of COVID-19 Lockdown Effects on Water Quality in Natural Bodies of Water in the Great Lakes Region. In : World Environmental and Water Resources Congress; 2021. p. 675–681. https://doi.org/10.1061/9780784483466.061

25. Haghnazar H, Cunningham JA, Kumar V, Aghayani E, Mehraein M. COVID-19 and urban rivers: Effects of lockdown period on surface water pollution and quality-A case study of the Zarjoub River, north of Iran. Environ. Sci. Pollut. Res. 2022;29:27382–27398. https://doi.org/10.1007/s11356-021-18286-5

26. Tokatlı C, Varol M. Impact of the COVID-19 lockdown period on surface water quality in the Meriç-Ergene River Basin, Northwest Turkey. Environ. Res. 2021;197:111051. https://doi.org/10.1016/j.envres.2021.111051

27. Arora S, Bhaukhandi KD, Mishra PK. Coronavirus lockdown helped the environment to bounce back. Sci. Total Environ. 2020;742:140573. https://doi.org/10.1016/j.scitotenv.2020.140573

28. Manoiu VM, Kubiak-Wójcicka K, Craciun AI, Akman Ç, Akman E. Water Quality and Water Pollution in Time of COVID-19: Positive and Negative Repercussions. Water. 2022;14:1124. https://doi.org/10.3390/w14071124

29. Balamurugan M, Kasiviswanathan KS, Ilampooranan I, Soundharajan BS. COVID-19 Lockdown disruptions on water resources, wastewater, and agriculture in India. Front. in Water. 2021;3:603531. https://doi.org/10.3389/frwa.2021.603531

30. Rupani PF, Nilashi M, Abumalloh RA, Asadi S, Samad S, Wang S. Coronavirus pandemic (COVID-19) and its natural environmental impacts. Int. J. Environ. Sci. Technol. 2020;17:4655–4566. https://doi.org/10.1007/s13762-020-02910-x

31. Water resources in India. [Internet]. [cited on 20 October 2021]. Available from: https://en.m.wikipedia.org/wiki/Water_resources_in_India

32. Save The River. [Internet]. 2020. [cited on 20 October 2021]. Available from: https://savetherivers.in/importance-of-rivers/

33. Rivers of India. [Internet]. [cited on 20 October 2021]. Available from: http://117.252.14.242/rbis/India_Information/rivers.htm

34. Singh S, Malik D, Thakur J, Kaur A, Singh RK, Nijhawan S. A comparative analysis of the physico-chemical properties and heavy metal pollution in three major rivers across India. Int. J. Sci. Res. 2014;3(8)1936–1941. Available from: https://www.researchgate.net/profile/R-K-Singh-4/publication/265168811_

35. Strokal M, Bai Z, Franssen W, et al. Urbanization: an increasing source of multiple pollutants to rivers in the 21st century. npj Urban Sustainability. 2021;1:1–3. https://doi.org/10.1038/s42949-021-00026-w

36. Singh M, Müller G, Singh IB. Heavy metals in freshly deposited stream sediments of rivers associated with urbanisation of the Ganga Plain, India. Water, Air, Soil Pollut. 2002;141:35–54. https://doi.org/10.1023/A:1021339917643

37. Spehar RL, Fiandt JT. Acute and chronic effects of water quality criteria-based metal mixtures on three aquatic species. Environ. Toxicol. Chem. 1986;5:917–931. https://doi.org/10.1002/etc.5620051008

38. Chabukdhara M, Nema AK. Assessment of heavy metal contamination in Hindon River sediments: a chemometric and geochemical approach. Chemosphere. 2012;87:945–53. https://doi.org/10.1016/j.chemosphere.2012.01.055

39. Duruibe JO, Ogwuegbu MO, Egwurugwu JN. Heavy metal pollution and human biotoxic effects. Int. J. Phys. Sci. 2007;2:112–118. Available from: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.933.1106&rep=rep1&type=pdf

40. Kerich EC. Households drinking water sources and treatment methods options in a regional irrigation scheme. J. Human, Earth, Future. 2020;1:10–19. https://doi.org/10.28991/HEF-2020-01-01-02

41. Owa FD. Water pollution: sources, effects, control and management. Mediterr. J. Soc. Sci. 2013;4:65. http://dx.doi.org/10.5901/mjss.2013.v4n8p65

42. Singh MR, Gupta A. Water pollution-sources, effects and control. Centre for Biodiversity, Department of Botany, Nagaland University; 2016. Available from: https://www.researchgate.net/profile/Asha-Gupta-6/publication/321289637_WATER_POLLUTION-SOURCESEFFECTS_AND_CONTROL/links/5a194005aca272df080a9dd3/WATER-POLLUTION-SOURCES-EFFECTS-AND-CONTROL.pdf

43. Singh AK, Chandra R. Pollutants released from the pulp paper industry: Aquatic toxicity and their health hazards. Aquat. Toxicol. 2019;211:202–16. https://doi.org/10.1016/j.aquatox.2019.04.007

44. Khan AS, Anavkar A, Ali A, Patel N, Alim H. A Review on Current Status of Riverine Pollution in India. Biosci., Biotechnol. Res. Asia. 2021;18(1)9–22. http://dx.doi.org/10.13005/bbra/2893

45. Kar D, Sur P, Mandai SK, Saha T, Kole RK. Assessment of heavy metal pollution in surface water. Int. J. Environ. Sci. Technol. 2008;Dec 1 5(1)119–24. https://doi.org/10.1007/BF03326004

46. Ramakrishna V, Babu BV. Fresh water depletion–a crisis: Causes & remedies. Environment & People. 1999;6(1)33–39. Available from: https://www.researchgate.net/profile/Galgotias-University/publication/237610803_FRESH_WATER_DEPLETION_-_A_CRISIS_CAUSES_REMEDIES/links/0c96053877fa242afc000000/FRESH-WATER-DEPLETION-A-CRISIS-CAUSES-REMEDIES.pdf

47. Anju A, Ravi SP, Bechan S. Water pollution with special reference to pesticide contamination in India. J Water Resour Protec. 2010;2010 http://dx.doi.org/10.4236/jwarp.2010.25050

48. Mohapatra SP, Gajbhiye VT, Agnihotri NP, Raina M. Insecticide pollution of Indian rivers. Environmentalist. 1995;1:41–44. https://doi.org/10.1007/BF01888888

49. National Research Council. An Assessment of the Health Risks of Seven Pesticides Used for Termite Control. Prepared for US Dept Navy, Washington, DC. 1982. https://doi.org/10.17226/665

50. Lindane (Gamma-Hexachlorocyclohexane). [Internet]. [Cited on 20 October 2021]. Avaliable from: https://www.epa.gov/sites/default/files/2016-09/documents/lindane.pdf

51. Hazardous Substances Fact Sheet-Methyl Parathion. [Internet]. [cited on 20 October 2021]. Available from: https://nj.gov/health/eoh/rtkweb/documents/fs/1283.pdf

52. Persistent Organic Pollutants Toolkit-Heptachlor. [Internet]. [Cited on 20 October 2021]. Available from: http://www.popstoolkit.com/about/chemical/heptachlor.aspx#:~:text=Heptachlor%20is%20a%20non%2Dsystemicis%20soluble%20in%20organic%20solvents

53. Nkosi BR, Odeku KO. A Comparative Perspective of Water Pollution Control. Mediterranean J. Social Sci. 2014;5(23)2600. http://dx.doi.org/10.5901/mjss.2014.v5n23p2600

54. Ganga Clean Up. [Internet]. 2017. [cited on 20 October 2021]. Available from: https://swachhindia.ndtv.com/ganga-action-plan-over-rs-4800-crore-spent-since-1986-says-ministry-of-environment-and-forests-9829/

55. Babu S. Curious case of Ganga Action Plan. [Internet]. 2009. [cited on 20 October 2021]. Available from: https://www.indiawaterportal.org/articles/curious-case-ganga-action-plan

56. Chaudhary M, Walker TR. River Ganga pollution: Causes and failed management plans. Environ. Int. 2019;126:202–206. https://doi.org/10.1016/j.envint.2019.02.033

57. Shrivastava SK. Clean Ganga and Yamuna mission a failure. [Internet]. 2012. [cited on 20 October 2021]. Available from: https://www.downtoearth.org.in/news/clean-ganga-and-yamuna-mission-a-failure-38246

58. Ministry of Jal Shakti. [Internet]. [cited on 20 October 2021]. Available from: https://www.pib.gov.in/PressReleseDetailm.aspx?PRID=1696301

59. Chopra L, Arora S. Pollution: Causes, Effects, Management and Recent Initiatives by Indian Government. Waste Management and Utilization Techniques. 157. https://www.researchgate.net/profile/Mohamed-El-Khateeb-3/publication/319631825_Environmental_pollution_prevention_via_heavy_metal_removal/links/59f89bc9458515547c269ca2/Environmental-pollution-prevention-via-heavy-metal-removal.pdf#page=169

60. National River Conservation Directorate. Ministry of Jal Shakti. [Internet]. [Cited on 20 October 2021]. Available from: https://nrcd.nic.in/

61. Parmar S, Singh V. Water quality parameters of river Yamuna in Delhi after 20 years of the Yamuna action plan. Int. J. Sci. Nature. 2015;6(4)662–669. Available from: https://www.researchgate.net/profile/Shobhika-Parmar/publication/286440112_WATER_QUALITY_PARAMETERS_OF_RIVER_YAMUNA_IN_DELHI_AFTER_20_YEARS_OF_THE_YAMUNA_ACTION_PLAN/links/5b5e7409458515c4b2522586/WATER-QUALITY-PARAMETERS-OF-RIVER-YAMUNA-IN-DELHI-AFTER-20-YEARS-OF-THE-YAMUNA-ACTION-PLAN.pdf

62. Sonune A, Ghate R. Developments in wastewater treatment methods. Desalination. 2004;167:55–63. https://doi.org/10.1016/j.desal.2004.06.113

63. Crini G, Lichtfouse E. Advantages and disadvantages of techniques used for wastewater treatment. Environ. Chem. Lett. 2019;17:145–155. https://doi.org/10.1007/s10311-018-0785-9

64. Awual MR, Yaita T, Suzuki S, Shiwaku H. Ultimate selenium (IV) monitoring and removal from water using a new class of organic ligand based composite adsorbent. J. Hazard. Mater. 2015;291:111–119. https://doi.org/10.1016/j.jhazmat.2015.02.066

65. Zinatloo-Ajabshir S, Morassaei MS, Amiri O, Salavati-Niasari M. Green synthesis of dysprosium stannate nanoparticles using Ficus carica extract as photocatalyst for the degradation of organic pollutants under visible irradiation. Ceram. Int. 2020;46:6095–6107. https://doi.org/10.1016/j.ceramint.2019.11.072

66. Zinatloo-Ajabshir S, Salehi Z, Salavati-Niasari M. Preparation, characterization and photocatalytic properties of Pr₂Ce₂O₇ nanostructures via a facile procedure. RSC Adv. 2016;6:107785–107792. https://doi.org/10.1039/C6RA18470G

67. Zinatloo-Ajabshir S, Emsaki M, Hosseinzadeh G. Innovative construction of a novel lanthanide cerate nanostructured photocatalyst for efficient treatment of contaminated water under sunlight. J. Colloid Interface Sci. 2022;619:1–13. https://doi.org/10.1016/j.jcis.2022.03.112

68. Mahdavi K, Zinatloo-Ajabshir S, Yousif QA, Salavati-Niasari M. Enhanced photocatalytic degradation of toxic contaminants using Dy₂O₃-SiO₂ ceramic nanostructured materials fabricated by a new, simple and rapid sonochemical approach. Ultrason. Sonochem. 2022;82:105892. https://doi.org/10.1016/j.ultsonch.2021.105892

69. Zonarsaghar A, Mousavi-Kamazani M, Zinatloo-Ajabshir S. Hydrothermal synthesis of CeVO4 nanostructures with different morphologies for electrochemical hydrogen storage. Ceram. Int. 2021;47:35248–32559. https://doi.org/10.1016/j.ceramint.2021.09.067

70. Zinatloo-Ajabshir S, Salavati-Niasari M. Facile route to synthesize zirconium dioxide (ZrO₂) nanostructures: structural, optical and photocatalytic studies. J. Mol. Liq. 2016;216:545–551. https://doi.org/10.1016/j.molliq.2016.01.062

71. Zinatloo-Ajabshir S, Morassaei MS, Amiri O, Salavati-Niasari M, Foong LK. Nd₂Sn₂O₇ nanostructures: green synthesis and characterization using date palm extract, a potential electrochemical hydrogen storage material. Ceram. Int. 2020;46:17186–17196. https://doi.org/10.1016/j.ceramint.2020.03.014

72. Zinatloo-Ajabshir S, Morassaei MS, Salavati-Niasari M. Eco-friendly synthesis of Nd₂Sn₂O₇-based nanostructure materials using grape juice as green fuel as photocatalyst for the degradation of erythrosine. Composites, Part B. 2019;167:643–653. https://doi.org/10.1016/j.compositesb.2019.03.045

73. Zinatloo-Ajabshir S, Ghasemian N, Mousavi-Kamazani M, Salavati-Niasari M. Effect of zirconia on improving NO_x reduction efficiency of Nd₂Zr₂O₇ nanostructure fabricated by a new, facile and green sonochemical approach. Ultrason. Sonochem. 2021;71:105376. https://doi.org/10.1016/j.ultsonch.2020.105376

74. Panagopoulos A. Techno-economic assessment of zero liquid discharge (ZLD) systems for sustainable treatment, minimization and valorization of seawater brine. J. Environ. Manage. 2022;306:114488. https://doi.org/10.1016/j.jenvman.2022.114488

75. Panagopoulos A. Water-energy nexus: desalination technologies and renewable energy sources. Environ. Sci. Pollut. Res. 2021;28:21009–21022. https://doi.org/10.1007/s11356-021-13332-8

76. Panagopoulos A, Haralambous KJ. Minimal Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) strategies for wastewater management and resource recovery-Analysis, challenges and prospects. J. Environ. Chem. Eng. 2020;8:104418. https://doi.org/10.1016/j.jece.2020.104418

77. Dias JM, Alvim-Ferraz MC, Almeida MF, Rivera-Utrilla J, Sánchez-Polo M. Waste materials for activated carbon preparation and its use in aqueous-phase treatment: a review. J. Environ. Manage. 2007;85:833–846. https://doi.org/10.1016/j.jenvman.2007.07.031

78. Awual MR. A novel facial composite adsorbent for enhanced copper (II) detection and removal from wastewater. Chem. Eng. J. 2015;266:368–375. https://doi.org/10.1016/j.cej.2014.12.094

79. Awual MR, Yaita T, Shiwaku H. Design a novel optical adsorbent for simultaneous ultra-trace cerium (III) detection, sorption and recovery. Chem. Eng. J. 2013;228:327–335. https://doi.org/10.1016/j.cej.2013.05.010

80. Awual MR. Assessing of lead (III) capturing from contaminated wastewater using ligand doped conjugate adsorbent. Chem. Eng. J. 2016;289:65–73. https://doi.org/10.1016/j.cej.2015.12.078

81. Awual MR. Ring size dependent crown ether based mesoporous adsorbent for high cesium adsorption from wastewater. Chem. Eng. J. 2016;303:539–546. https://doi.org/10.1016/j.cej.2016.06.040

82. Arora G, Yadav M, Gaur R, et al. Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation. Nanoscale. 2021;13:10967–11003. https://doi.org/10.1039/D1NR01010G

83. Sharma RK, Pandey A, Gulati S, Adholeya A. Silica modified with 2, 6-diacetylpyridine-monosalicyloylhydrazone: a novel and selective organic–inorganic sorbent for separation of molybdenum ions in a newly designed reactor. Chem. Eng. J. 2012;210:490–499. https://doi.org/10.1016/j.cej.2012.09.022

84. Sharma RK, Pandey A, Gulati S, Adholeya A. An optimized procedure for preconcentration, determination and on-line recovery of palladium using highly selective diphenyldiketone-monothiosemicarbazone modified silica gel. J. Hazard. Mater. 2012;209:285–292. https://doi.org/10.1016/j.jhazmat.2012.01.022

85. Sharma RK, Solanki K, Dixit R, Sharma S, Dutta S. Nanoengineered iron oxide-based sorbents for separation of various water pollutants: current status, opportunities and future outlook. Environ. Sci.: Water Res. Technol. 2021;7:818–860. https://doi.org/10.1039/D1EW00108F

86. Yadav M, Gupta R, Arora G, Yadav P, Srivastava A, Sharma RK. Current status of heavy metal contaminants and their removal/recovery techniques. Contaminants in Our Water: Identification and Remediation Methods. American Chemical Society; 2020. p. 41–64.

87. Sharma RK, Pant P. Preconcentration and determination of trace metal ions from aqueous samples by newly developed gallic acid modified Amberlite XAD-16 chelating resin. J. Hazard. Mater. 2009;163:295–301. https://doi.org/10.1016/j.jhazmat.2008.06.120

88. Sharma RK, Pant P. Solid phase extraction and determination of metal ions in aqueous samples using Quercetin modified Amberlite XAD-16 chelating polymer as metal extractant. Int. J. Environ. Anal. Chem. 2009;89:503–514. https://doi.org/10.1080/03067310802691680

89. Sharma RK, Gulati S, Pandey A, Adholeya A. Novel, efficient and recyclable silica based organic–inorganic hybrid Nickel catalyst for degradation of dye pollutants in a newly designed chemical reactor. Appl. Catal. B. 2012;125:247–258. https://doi.org/10.1016/j.apcatb.2012.05.046

90. Sharma RK, Arora B, Sharma S, et al. In situ hydroxyl radical generation using the synergism of the Co-Ni bimetallic centres of a developed nanocatalyst with potent efficiency for degrading toxic water pollutants. Mater. Chem. Front. 2020;4:605–620. https://doi.org/10.1039/C9QM00628A

91. Sharma RK, Yadav S, Gupta R, Arora G. Synthesis of magnetic nanoparticles using potato extract for dye degradation: A green chemistry experiment. J. Chem. Edu. 2019;96:3038–3044. https://doi.org/10.1021/acs.jchemed.9b00384

92. Awual MR. Solid phase sensitive palladium (II) ions detection and recovery using ligand based efficient conjugate nanomaterials. Chem. Eng. J. 2016;300:264–272. https://doi.org/10.1016/j.cej.2016.04.071

93. Awual MR, Yaita T, Kobayashi T, Shiwaku H, Suzuki S. Improving cesium removal to clean-up the contaminated water using modified conjugate material. J. Environ. Chem. Eng. 2020;8:103684. https://doi.org/10.1016/j.jece.2020.103684

94. Awual MR. A facile composite material for enhanced cadmium (II) ion capturing from wastewater. J. Environ. Chem. Eng. 2019;7:103378. https://doi.org/10.1016/j.jece.2019.103378

95. Awual MR, Hasan MM. A ligand based innovative composite material for selective lead (II) capturing from wastewater. J. Mol. Liq. 2019;294:111679. https://doi.org/10.1016/j.molliq.2019.111679

96. Awual MR, Yaita T, Shiwaku H, Suzuki S. A sensitive ligand embedded nano-conjugate adsorbent for effective cobalt (II) ions capturing from contaminated water. Chem. Eng. J. 2015;276:1–10. https://doi.org/10.1016/j.cej.2015.04.058

97. Islam A, Teo SH, Awual MR, Taufiq-Yap YH. Improving the hydrogen production from water over MgO promoted Ni-Si/CNTs photocatalyst. J. Clean. Prod. 2019;238:117887. https://doi.org/10.1016/j.jclepro.2019.117887

98. Hasan MN, Shenashen MA, Hasan MM, Znad H, Awual MR. Assessing of cesium removal from wastewater using functionalized wood cellulosic adsorbent. Chemosphere. 2021;270:128668. https://doi.org/10.1016/j.chemosphere.2020.128668

99. Awual MR. Novel ligand functionalized composite material for efficient copper (II) capturing from wastewater sample. Compos. B. Eng. 2019;172:387–396. https://doi.org/10.1016/j.compositesb.2019.05.103

100. Awual MR. Efficient phosphate removal from water for controlling eutrophication using novel composite adsorbent. J. Clean. Prod. 2019;228:1311–1319. https://doi.org/10.1016/j.jclepro.2019.04.325

101. Kubra KT, Salman MS, Hasan MN, Islam A, Hasan MM, Awual MR. Utilizing an alternative composite material for effective copper (II) ion capturing from wastewater. J. Mol. Liq. 2021;336:116325. https://doi.org/10.1016/j.molliq.2021.116325

102. Bolisetty S, Peydayesh M, Mezzenga R. Sustainable technologies for water purification from heavy metals: review and analysis. Chem. Soc. Rev. 2019;48:463–487. https://doi.org/10.1039/C8CS00493E

103. Bashir A, Malik LA, Ahad S, et al. Removal of heavy metal ions from aqueous system by ion-exchange and biosorption methods. Environ. Chem. Lett. 2019;17:729–754. https://doi.org/10.1007/s10311-018-00828-y

104. Central Pollution Control Board. Assessment of Impact of Lockdown on Water Quality of Major Rivers. [Internet]. 2020. [Cited on 20 October 2021]. Available from: https://cpcb.nic.in/upload/Assessment-of-Impact-Lockdown-WQ-MajorRivers.pdf

105. Dutta V, Dubey D, Kumar S. Cleaning the River Ganga: Impact of lockdown on water quality and future implications on river rejuvenation strategies. Sci. Total Environ. 2020;743:140756. https://doi.org/10.1016/j.scitotenv.2020.140756

106. Patel PP, Mondal S, Ghosh KG. Some respite for India’s dirtiest river? Examining the Yamuna’s water quality at Delhi during the COVID-19 lockdown period. Sci. Total Environ. 2020;744:140851. https://doi.org/10.1016/j.scitotenv.2020.140851

107. Khan R, Saxena A, Shukla S. Assessment of the impact of COVID-19 lockdown on the heavy metal pollution in the River Gomti, Lucknow city, Uttar Pradesh, India. Environ Qual Manag. 2021;1–9. https://doi.org/10.1002/tqem.21746

108. Chakraborty B, Roy S, Bera A, et al. Cleaning the river Damodar (India): impact of COVID-19 lockdown on water quality and future rejuvenation strategies. Environ. Dev. Sustainability. 2021;23:11975–11989. https://doi.org/10.1007/s10668-020-01152-8

109. Patil SN, Prasad SR. An Impact of Nationwide Lockdown on Physico-chemical Parameters of Bhogavati River Water. ES Energy & Environ. 2020;11:28–39. https://dx.doi.org/10.30919/esee8c931

110. Dissolved Oxygen. [Internet]. [Cited on 20 October 2021]. Available from: https://www.enr.gov.nt.ca/sites/enr/files/dissolved_oxygen.pdf

111. Central Water Commission. [Internet]. [Cited on 20 October 2021]. Available from: http://cwc.gov.in/water-quality-status-rivers-india

112. Biological Oxygen Demand [Internet]. [Cited on 20 October 2021] Available from:https://www.researchgate.net/post/What_is_the_permeable_limit_of_Biochemical_Oxygen_Demand_BOD_in_wastewater_discharge

113. Rahmanian N, Ali SH, Homayoonfard M, et al. Analysis of physiochemical parameters to evaluate the drinking water quality in the State of Perak, Malaysia. J. Chem. 2015;2015:716125 https://doi.org/10.1155/2015/716125

114. Singh RK, Chaturvedi A, Kumari K. Water-quality assessment of Damodar River and its tributaries and subtributaries in Dhanbad Coal mining areas of India based on WQI. Sustainable Water Resour. Manag. 2019;5:381–386. https://doi.org/10.1007/s40899-017-0159-7

115. Seth BL. Centre for Science and Environment. [Internet]. [cited on 20 October 2021]. Available from: https://www.cseindia.org/content/downloadreports/7996

116. Schellenberg T, Subramanian V, Ganeshan G, Tompkins D, Pradeep R. Wastewater discharge standards in the evolving context of urban sustainability-The case of India. Front. Environ. Sci. 2020;8:30. https://doi.org/10.3389/fenvs.2020.00030

117. TimesTravel. Lockdown effect: Gangetic dolphins spotted at Kolkata ghats after 30 years. [Internet]. 2020. [Cited on 20 October 2021]. Available from: https://timesofindia.indiatimes.com/travel/things-to-do/lockdown-effect-gangetic-dolphins-spotted-at-kolkata-ghats-after-30-years/articleshow/75375783.cms

118. ActionAid Association (India). River Ecology: An assessment of the impact of the COVID-19 lockdown 2020. [Internet]. 2020. [Cited on 20 October 2021]. Available from: https://www.actionaidindia.org/wp-content/uploads/2020/09/River-Ecology-An-assessment-of-the-impact-of-COVID-19-lockdown-V3.pdf

119. Jain SK. Water resources management in India-challenges and the way forward. Curr. Sci. 2019;117:569–576. https://doi.org/10.18520/cs/v117/i4/569-576

120. S Sen S. Environmental Flow Concept and Ground Reality: Around the World and India. 2021. Available from: https://www.researchgate.net/publication/349287928_Environmental_Flow_Concept_and_Ground_Reality_Around_the_World_and_India

121. Central Pollution Control Board. General standards for discharge of environmental Pollutants. [Internet]. [cited 25 March 2022]. Available from: https://cpcb.nic.in/displaypdf.php?id=R2VuZXJhbFN0YW5kYXJkcy5wZGY=

Fig. 1

Overview of different chemicals production in India. (Data Source: GoI, Annual Report 2020–21)

Fig. 2

Timeline of different river cleaning plans by government of India.

Fig. 3

Variation in pH and heavy metals (μg/L) across all sites in a) pre COVID-19 lockdown phase (October 2019) and b) amid lockdown in June 2020. Reproduced with permission from ref. [107]

Fig. 4

Showing betterment in parameters like pH, TDS, hardness, EC during lockdown period. Reproduced with permission from ref [109].

Fig. 5

Changes in aquatic species.

Table 1

Major Pollutants Present in Indian Rivers, their Sources and Toxic Effects on Living Species.

Major Pollutants	Key Sources	Toxicity and adverse effects	Ref.
Inorganic Pollutants
Arsenic	Pulp paper industries, laboratory waste, etc.	Cause cancer of lungs, liver, bladder and skin and arsenic skin lesion, neurological problems, pulmonary disease, peripheral vascular disease, hypertension, and cardiovascular disease	[42, 43]
Lead	Pulp paper, paint, glass and Industries, household, laboratory waste, etc.	Affects blood, central nervous system and the kidneys, damages the neurologic, hematologic, and renal systems in human and causes cognitive impairment in children, peripheral neuropathy in adults, and developmental delay.	[42–45]
Mercury	Metal, electroplating and thermal power plant industries, laboratory waste, etc.	Minamata disease, Chromosomal aberrations and neurological damages to humans. In aquatic ecosystem it causes biomagnification.	[42–44]
Cadmium	Electroplating, preparation of Cd-Ni battery, control rods, shields for nuclear reactor, television phosphors, etc.	Itai-itai disease, nephritis and nephrosis kidney and liver damage, renal dysfunction and gastrointestinal damage. Toxic to the kidney of the sea bass.	[42–44]
Copper	Electroplating, pulp paper industry, pesticide, production mining, etc.	Headache, nausea, vomiting, diarrhoea and kidney malfunctioning. Lipid peroxidation and DNA damage in the European eel.	[43–45]
Zinc	Effluents from electroplating and pulp paper industries, sewage discharge, immersion of painted idols, etc.	Vomiting, diarrhoea, icterus, liver and kidney damage, the neurological and nervous system, damage the fetal brain.	[43–45]
Chromium	Mines, electroplating, sulphite pulping, etc.	Gastrointestinal, hepatic, renal, neuronal damage, carcinogenic in human and harmful effects of chromium on DNA have been described in fish, DNA damage of Chinook salmon.	[43, 44]
Nickel	Stainless steel manufacturing units, electroplating factory discharge, pulp paper industry, etc.	Neurotoxic, genotoxic and carcinogenic agent, nickel dermatitis, causes oxidative stress to fish.	[43–45]
Alkaline earth metals	Pulp paper industries, laboratory waste, etc.	Ca and Mg causes neurotoxicity, toxicity to juvenile channel catfish, Ba affects the nervous system, causing cardiac irregularities and tremors.	[43, 45]
Anions (like Cl⁻, SO₄²⁻, PO₄³⁻, NO₃⁻, CO₃²⁻, Cr₂O₇²⁻, etc.)	Rainwater from polluted soil surface, detergents, industrial, household, laboratory waste, etc.	Cl⁻, SO₄²⁻, NO₃⁻, CO₃²⁻ causes acidification and hardening of water which disturbs the pH level thus affecting the nutrient cycle, PO₄³⁻ causes retarded growth of plants, elongation of roots, CO₂ fixation, photosynthesis, cation uptake, pollen germination and growth of pollen tubes, destruction of chlorophylls and cell membranes, Cr₂O₇²⁻ is carcinogenic.	[42, 46]
Fluorides	Industrial, household, laboratory waste, etc.	Concentration less than 0.5 mg L⁻¹ causes dental carries and mottling of teeth but prolonged exposure to higher levels above 0.5 mg L⁻¹ lead to adverse effect on human health leading to fluorosis.	[42]
Organic Pollutants
Chlorophenol	Pulp and paper industries, etc.	Estrogenic and mutagenic disorder, affect oxidative phosphorylation, and prevent ATP synthesis.	[43]
Tannins	Pulp and paper industries, etc.	Inhibition of several enzymatic activities in the fish.	[43, 44]
Resin acids and fatty acid	Pulp and paper industries, etc.	Inhibit methanogenic bacteria which makes the anaerobic treatment of wastewaters troublesome	[43]
Dioxins and furans	Pulp and paper industries, etc.	Leads to biomagnification into food chains and various degrees of toxic effects occurs.	[43]
Biocide	Pulp and paper industries, etc.	Neurotoxic effects, many of them are carcinogenic, and have effects on the reproduction and cell development, especially in the early stages of life.	[43]
Nonylphenol ethoxycarboxylates	Pulp and paper industries, etc.	Kidneys and hormone levels in humans.	[43]
Nitrilotriacetic acid, EDTA^, DTPA^	Pulp and paper industries, etc.	Hydronephrosis and nephromegaly to humans.	[43]
DDT^*	Pesticide from agricultural activities, etc.	Carcinogenic, causes vomiting, tremors and seizures.	[47, 48]
beta-HCH^*	Pesticide from agricultural activities, etc.	Carcinogenic.	[47, 48]
Aldrin and Dieldrin	Pesticide from agricultural activities, etc.	Headache, dizziness, nausea, general malaise and vomiting, followed by muscle twitching, myoclonic jerks and convulsions.	[49]
Gamma-HCH or lindane	Insecticides from agricultural activities, etc.	Irritation of the nose and throat, anaemia and skin effects, effects on the nervous system, such as seizures and convulsions, effects on the cardiovascular and musculoskeletal systems.	[50]
Methyl parathion	Insecticides from agricultural activities, etc.	Causes rapid, fatal, organophosphate poisoning with headache, dizziness, blurred vision, tightness in the chest, sweating, nausea and vomiting, diarrhoea, muscle twitching, convulsions, coma and death.	[51]
Heptachlor	Insecticides from agricultural activities, etc.	Headache, dizziness, incoordination, tremors, and seizures.	[52]
Induction of coliform bacteria due to contamination of PPI waste water	Pulp and paper industries, etc.	fishes have been noted an adverse effect on their reproductive system in multiple ways i.e., masculinization, lower plasma sex hormone, reduced gonad size, and reduced vitellogenin in the female, circulating sex hormone, fecundity, delayed maturity and change in secondary sex characteristics.	[43]
Crude Oil	Oil spillage	Depletes the oxygen content of water body by reducing light transmission, inhibiting the growth of planktons and photosynthesis in macrophytes	[42]
Macrophytes (like Salvinia, Azolla, Eichhornia)	Sewage and drain water, etc.	Reduced dissolved oxygen (DO) and increased biological oxygen demand (BOD).	[42, 43]
Micro-organisms (like Salmonella sp., Shigella sp., Escherichia coli and Vibrio cholera)	Contaminated water bodies from fecal coliform of E. Coli.	It causes typhoid fever, diarrhoea, dysentery, gastroenteritis and cholera. Ground water contamination, according to Larry 2006, leads to death of more than 14000 people daily around the world.	[42, 43]
Fly ash	Industrial waste, vehicular emissions, etc.	Oxygen cut-off in aqua culture and reduced uptake of essentials leading to plant death.	[42]
Thermal waste water	Industrial, household, nuclear and laboratory waste, etc.	Oxygen depletion, reduced photosynthesis rate due to inhibition of enzyme activity with increased temperature.	[42]

EDTA is ethylenediaminetetraacetic acid; DTPA is Diethylenetriamine pentaacetate; DDT is Dichlorodiphenyltrichloroethane and beta-HCH is beta-hexachlorocyclohexane.

Table 2

Strengths, Achievements and Weaknesses of Different Government Schemes to Clean Major Rivers of India.

Scheme	Total Investment	Strengths	Weaknesses	References
GAP	Rs. 462.04 Cr. (360.96 million USD)	- Initial Vision - Nalas Interception and Diversion Strategy - Establishment of Institutional Infrastructure - Making local governments and state governments pay for operations and maintenance - Peer review and oversight by a variety of stakeholders - Appointment of independent agencies to monitor water quality	- The extent of the concerns covered is limited - In the Ganga Basin, there is partial coverage in terms of sewage collection, treatment, and disposal. - Failure to make use of existing monitoring data - Failure to monitor and regulate industrial pollution, resulting in its control. - Inconsistent upkeep - Assets that aren’t performing as well as they should - Finance models that are unclear and unviable - The impact of aid on planning in general, and programme prioritisation and technology selection in particular - The absence of a well-defined policy, legal, and institutional structure - Inappropriate policy of dumping treated sewage and effluent into the river	[1,2,3,4]
NGRBA	Rs. 4607.82 Cr. (951.82 million USD)	- A more holistic, basin-wide, and multi-sectoral strategy - Strong institutional framework - Regulatory and developmental roles - Optimal asset performance	- Inadequate research and data - Lack of political will - Inadequate monitoring leads to encroachment and diversion of land for development and building - The Ganga and its tributaries’ ecological flows were not factored into the basin management plan - The importance of major and minor tributaries was overlooked in the basin-wide environment management strategy - Municipal and planning authorities’ lack of long-term participation	[2,3,4]
NMGC or Namami Gange Project	Rs. 20,000 Cr. (3208.72 million USD)	- Development along the river - Massive financing from government agencies - Preservation of biodiversity - Ganga basin reforestation - A five-state Ganga committee for effective project monitoring - New sewage treatment plants - 887 MLD of current STPs will be rehabilitated - Public awareness campaign - Monitoring of industrial effluents by the use of real-time water quality monitoring stations	- Inadequate policy and legal framework - There is a lack of cooperation among the many riparian governments - There has been a little attention on the river’s ecological and geological integrity, and minor tributaries of the Ganga have not been included thus far - There are insufficient environmental flow allocations - Inadequate industrial pollution control	[3,4,5]
YAP (GAP phase II)	Rs. 2285.48 Cr. (749.58 million USD)	- New infrastructure is being built to prevent raw sewage from overflowing - Utilization of an upflow unaerobic sludge blanket (UASB) reactor and an oxidation pond - Disinfection of STP effluents pilot - Access to low-cost sanitation - Decentralised STPs as a test bed - Non-sewerage components and a few unorthodox interventions that have an impact on river pollution (such as improved crematoria, river front development, and public engagement and community awareness)	- Inadequate budgetary allocations and resources for the operation and maintenance of wastewater treatment facilities have resulted in - A primary focus on the engineering-centric approach has resulted in - No focus on river ecological entities has resulted in - A lack of cooperation between central and state governments and municipal authorities has resulted in	[4,6]

Table 3

Comparing Water Quality Parameters of the Rivers Discussed Above Before and During the Lockdown.

S. No.	Water quality parameter	Site/State	Name of the river	Permissible limit	Before lockdown	During lockdown	Ref.
1.	DO (mg L⁻¹)	Maharashtra (For 14 monitored sites)	Godavari	6.5–8	3.1–6.9	5–6.8	[104, 110]
		Maighat	Gomti	6.5–8	6.20	6.35	[110, 111]
		Uttarakhand (For 6 monitored sites)	Ganga	6.5–8	9.6–11.6	9.8–10.6	[104, 110]
		Delhi (For 5 monitored sites pre-lockdown and 3 monitored sites during lockdown)	Yamuna	6.5–8	17.1	1.2–8.3	[104, 110]

2.	BOD (mg L⁻¹)	Maharashtra (For 14 monitored sites)	Godavari	<5	2.2–8.8	2.4–6.2	[104, 112]
		Maighat	Gomti	<5	3.72	3.50	[111, 112]
		Uttarakhand (For 6 monitored sites)	Ganga	<5	1.0–1.2	0.6–1.2	[104, 112]
		Delhi (For 5 monitored sites pre-lockdown and 3 monitored sites during lockdown)	Yamuna	<5	7.9–78	2–6.1	[104, 112]

3.	pH	Maharashtra (For 14 monitored sites	Godavari	6.5–8.5	7.1–8.1	7–8.1	[104, 113]
		Maighat	Gomti	6.5–8.5	8.48	8.76	[111, 113]
		Uttarakhand (For 6 monitored sites)	Ganga	6.5–8.5	6.6–7.9	7.5–8.2	[104, 113]
		Delhi (For 5 monitored sites pre-lockdown and 3 monitored sites during lockdown)	Yamuna	6.5–8.5	7.2–8.7	7.1–7.8	[104, 113]
		Uttar Pradesh (For 10 monitored stations)	Damodar	6.5–8.5	7.04–8.21	6.12–7.72	[113, 114]

4.	Electrical conductivity (μS cm⁻¹)	Bhadrachalam	Godavari	<1000	307	212	[111, 115]
		Varanasi	Ganga	<1000	485	542	[111, 115]
		Delhi	Yamuna	<1000	688–2485	273–1657	[111, 115]
		Uttar Pradesh (For 10 monitored stations)	Damodar	<1000	1040–1260	750–880	[114, 115]

5.	FC (MPN/100mL)	Maharashtra (For 14 monitored sites	Godavari	<500	2–70	2–47	[104, 116]
		Uttarakhand (For 6 monitored sites)	Ganga	<500	17–60	12–60	[104, 116]
		Delhi (For 5 monitored sites pre-lockdown and 3 monitored sites during lockdown)	Yamuna	<500	1300–920000	No data available	[104, 116]

6.	COD (mg L⁻¹)	Maighat	Gomti	250	31	34	[111]
		Uttar Pradesh	Ganga	250	6.14–17.7	6.0–33.2	[116]
		Delhi	Yamuna	250	28 to 574	6 to 383	[111]