The benefits of restoring urban lakes in the tropics.

Lake restoration in developing economies, particularly in the tropics, is a major challenge given the severe levels of pollution from untreated wastewater and the warm climate conducive to microbial and algal growth. Restoration goals are often ill-defined or unachievable. Here we describe the successes that can be achieved through a control, compared with intervention case study of the two urban lakes in Bengaluru, India, one of the world's largest and fastest growing mega-cities. The unrestored control, Bellandur Lake, was severely polluted by 231 million litres per day (MLD) of untreated wastewater. The restoration site, Jakkur Lake, receives 10 MLD of treated wastewater and also receives some tertiary treatment by circulating the effluent through a constructed wetland before it enters the lake. The water quality of Bellandur Lake can only be described as extremely bad. Organic pollution levels in the main inflow were high (BOD5 of 199 mg/l, faecal coliforms 6.9 Log MPN/100 ml, total suspended solids (TSS) of 285 mg/l) leading to the complete deoxygenation of lake even at the surface. The levels exceeded use-base standards for bathing water and fisheries. The high levels of organic pollution and low oxygen conditions also led to extreme levels of methane emissions that occasionally led to the lake surface catching fire. Total nitrogen (TN) and total phosphorus (TP) concentrations in the lake were extremely high (47 mg/l and 6.3 mg/l) respectively with low Secchi depth (SD). Despite the high nutrient levels, very little phytoplankton growth occurred (chlorophyll-a of 0 mg/l), most likely due to the high TSS loads which restricted light availability. In comparison, the wastewater treatment and wetland at Jakkur Lake markedly reduced organic pollution of the main inflow (BOD5 of 32 mg/l, faecal coliforms 4.1 Log MPN/100 ml, TSS of 48 mg/l). Levels of coliforms in the lake were above the standards for bathing waters. Total nitrogen (TN) and total phosphorus (TP) concentrations in the lake reduced (10.5 mg/l, 2.4 mg/l) but still classify the lake as extremely hypereutrophic. The lower TSS levels did, however, enable dense phytoplankton blooms to develop (max chlorophyll-a of 600 µg/l) which are in part responsible for the higher levels of dissolved oxygen in the lake water, albeit and as expected with large diurnal fluctuations. The comparison highlights the benefits that standard wastewater treatment provides to restore urban tropical lakes in context of rapidly urbanising catchments, and even though Jakkur Lake is by no means fully restored, it sustains water quality that allow propagation of fisheries and shore-based recreation. It also greatly contributes to greenhouse gas emission reductions. Further restoration measures are likely needed for urban tropical lakes, particularly to tackle pollutant loads in monsoon periods, but restoring community pride in the uses of a lake is an important milestone of the restoration efforts.

Environmental surveillance of antimicrobial resistance in a rapidly developing catchment.

Development and spread of AMR from various sources such as hospitals, pharmaceutical industries, animal farms and human habitations is not well understood. We conducted a pilot study to assess the prevalence of AMR by taking a case of rapidly developing catchment in Western India. For this, we selected four sub-catchments/regions with a dominant source of antibiotics, viz. areas with (a) dense poultry farms (4 farms/km2), (b) sparse number of poultry farms (2 farms/km2), (c) agricultural fields and (d) habitation (village). The environmental samples (soil, litter and water) were subjected to Kirby-Bauer/antibiotic disc susceptibility test to assess the resistance pattern in the bacterial species. Preliminary investigations showed the presence of seven multidrug-resistant bacterial species in the litter from poultry farms, with five species having a MAR index greater than 0.2. No evidence of AMR was observed in the vicinity (water and soil) of the poultry farms. This could be attributed to the rigorous disinfection protocols followed at the poultry farms to prevent infection in the fresh batch of chickens. However, in agricultural fields where the litter is used as manure, seven multiple drugs resistant with two species scoring a MAR index greater than 0.2 were observed. MAR index of less than 0.2 was observed for Escherichia coli and Enterobacter species isolated from village and control site (soil), respectively, indicating negligible contamination by antibiotics at sub-catchments. This study provides an approach to investigate the effects of multiple factors on the prevalence of AMR at the catchment scale.

A multi-pronged approach to source attribution and apportionment of heavy metals in urban rivers.

Heavy metal (HM) contamination of water bodies is caused by both first generation (industries) and second generation (distributed sources, domestic sewage, sediments) sources. We applied a multi-pronged approach to quantify the contribution of first and second generation sources to the HM load in a stream located in an industrialised catchment. We found that, despite strict regulation, first generation sources contributed significantly to the HM load (60%-80%), showing the ineffectiveness of current regulation. Domestic sewage contributed significantly to Cu, Ni, and Mn load (15%-20%). The contribution of distributed sources and sediments to HM load is insignificant. In a 24-hour cycle, HM concentrations frequently exceeded FAO's irrigation water quality standards, with the highest concentrations observed at night. Empirically, the study highlights the continued plight of urban streams in rapidly industrialising centers and the failure to regulate first-generation sources. Methodologically, it demonstrates the importance of temporally intensive measurement of contaminant concentration and load. Policy implications include the need for ambient water quality standards, inclusion of HMs in such standards, load-based regulation, and a problem-oriented monitoring and enforcement approach.

Sustenance of Himalayan springs in an emerging water crisis.

Springs are a significant source of high quality and perennial freshwater supply for remote communities and sustain rich biodiversity and ecosystems in the Himalayas. About 60-70% of the Himalayan population directly depends on springs to meet their domestic and livelihood needs. Despite that, decline in approximately 60% of low discharge springs have been reported in the last couple of decades. In addition, nitrates and faecal coliform contamination linked to septic tanks, open defecation, and fertiliser application have been reported. A high degree of urbanization with 500 growing townships and 8-10 large cities has further threatened the sustenance of these vital resources, causing a severe water crisis in the Himalayas. Spring rejuvenation can enhance water access and livelihoods and help achieve several sustainable development goals (SDGs). However, multiple challenges hinder the success of such initiatives. A fundamental limitation is the poor understanding of complex groundwater (spring) systems and their interactions with human societies. This review identified crucial knowledge gaps by synthesizing available knowledge on springs and revival efforts from peer-reviewed journals and reports by practitioners and governing bodies. The review also highlights the limitations of spring revival approaches and recommends future management options. There is a critical lack of comprehensive data as a large research on the Himalayan spring systems results from small-scale spring centric studies focussing primarily on hydrology. In contrast, the impacts of hydrogeology, ecology, socio-economics and developmental activities on springs are less explored. Lack of scientific inputs on the hydrogeological regime and limited support by the state is a barrier to scaling spring rejuvenation programs. Long term monitoring, location-specific mapping of local hydrogeological and socio-economic settings at aquifer scale and collaborations among different stakeholders are essential to facilitate holistic knowledge development on spring systems and successful spring revival. The authors recommend ensuring sustenance by recognizing the value of springs in the mainstream programs and policies and develop appropriate management framework for the management of spring systems.

A novel approach to baseline water quality assessment at local and catchment scale: a case study from Berambadi, India.

Optimal design and maintenance are necessary for the sustainability of wastewater treatment systems. In this study, we present the outcome of a novel approach to baseline assessment conducted prior to the design and deployment of a decentralized wastewater treatment system at a school in rural India. The baseline water quality monitoring protocol was deployed to assess (a) the quality and quantity of wastewater (greywater and blackwater) flows from the school and (b) the status of surface water and groundwater quality in the catchment. Hourly greywater flows and water quality trends were monitored across four seasons at the school. Average freshwater consumption at the school was 518 ± 322 L/day for hand washing and 287 ± 97 L/day for cooking meals. Greywater generation showed high hourly variations in COD levels. Greywater generated from hand wash and kitchen sources contributed to 110 g/day and 96 g/day of BOD5 respectively and 214 g/day and 141 g/day of COD respectively. Based on additional data from a self-reporting sanitation survey, the organic contaminant load generated from the toilet was estimated to be 1.5 ± 0.1 kg COD/day. At the catchment scale, both groundwater and surface water quality were monitored seasonally to assess the impact of raw sewage and stormwater inputs. Compared with borewells, high nitrate-N levels (> 10 mg/L) were observed in the village hand pump samples throughout the year. Maximum nitrate-N (16 mg/L) and fecal coliforms (3.9 log MPN/100 mL) levels were observed in surface waters during monsoons, indicating the impact of sewage and surface runoff on water quality. The proposed approach is useful to estimate data on freshwater use and wastewater generation at the school and hence to make the case for, and design of, a sustainable water management intervention.

Greenhouse gas budgets of severely polluted urban lakes in India.

Inland waters are important sources of greenhouse gases and emissions from polluted subtropical systems may be contributing to the observed global increase in atmospheric methane concentrations. Here we detail a scoping study where dissolved concentrations of greenhouse gases methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) were measured in two contrasting urban lakes in Bangalore (Bengaluru), Karnataka, India, from June 2018 to February 2020. Bellandur Lake is a severely polluted system whilst Jakkur Lake has been subject to partial restoration via treatment of organic matter inputs. Methane concentrations in Bellandur Lake were three orders of magnitude higher than in Jakkur Lake, with a mean concentration of 3.02 ± 1.57 mg CH4-C L-1 compared to 1.72 ± 1.22 µg CH4-C L-1. At Bellandur Lake, dissolved CO2 concentrations were of the same order of magnitude as for CH4, whereas at Jakkur Lake dissolved CO2 concentrations were two orders of magnitude greater than for CH4. Concentrations of N2O were negligible in both lakes. Extrapolating our data to estimate greenhouse gas fluxes, mean daily methane fluxes from Bellandur Lake were consistently in excess of 1000 mg CH4 m2 d-1, rendering the lake a source of GHGs to the order of 148,350 ± 21,790 ton yr-1 CO2-e yr-1, compared to 100 ± 37 ton CO2-e yr-1 from Jakkur Lake, with CH4 contributing primarily to this difference. We propose that the contribution of severely polluted urban lakes to global CH4 production warrants further investigation, particularly as our evidence suggests that standard secondary wastewater treatment to support restoration of these systems has the potential to significantly reduce CH4 emissions.

Sustainable water resources through harvesting rainwater and the effectiveness of a low-cost water treatment.

Increases in world population and climate change are some of the pressures affecting water resources for current and future water availability. The variability in water availability can reduce agricultural yields, food supplies and potentially leads to malnutrition and spread of diseases in water-poor countries. Even some water-rich countries can experience prolonged periods of dry weather, causing a drop in water reservoirs levels, forcing more restricted water resources management. Rainwater harvesting is one key option in adapting to water shortage and future demands that may alleviate the pressure on existing water resources. This work evaluates a roof top rainwater harvesting system (RWHS) installed as part of a decentralised wastewater treatment system designed to enable a circular economy by providing a more reliable water supply system in a remote public school in rural India. The effectiveness of the RWHS in reducing the pressure on a groundwater supply was assessed along with the physical, chemical and microbial characteristics of the stored rainwater over time. Further, the application of a low-cost primary treatment to make the harvested water safe to use for multiple purposes was investigated. The results revealed that the harvested water was of acceptable quality at the start of collection, however, microbial abundance increased when the rainwater was stored for a long time without treatment. Thus, a chlorine dosing regimen for the RWHS was designed based on laboratory and field experiments. The results also demonstrated that the low-cost chlorination process was effective in the field in reducing microbial abundance in the stored water for more than 30 days. However, as the residual chlorine level was reduced with time to <0.2 mg/l in the storage vessel, the microbial abundance increased, albeit to a much lower level that meets the Indian bathing water standards. The results provide evidence that installed RWHS has reduced the pressure on existing water supply at the school by up to 25% of the water that used for washing and flushing with no treatment, and with regular chlorination, greater savings and multiple uses of the stored rainwater can be achieved.

Provisional green infrastructure: transdisciplinary approaches to address contamination in urban streams.

Surface water contamination has emerged as an area of major concern in rapidly growing cities in the Global South, including and especially in the Indian megacity context. We argue here that nallahs (open drainage channels in Indian megacities) should be more widely recognized as a potential locus of intervention. These combined stormwater and wastewater networks offer opportunities for flexible, frugal and inclusive retrofits to improve surface and groundwater quality. We propose and define the concept of provisional green infrastructure (PGI) as a speculative innovation typology describing in-stream interventions. We argue that PGI should be employed as a shared boundary concept guiding transdisciplinary action and research within the highly unpredictable, space-constrained, and contaminated watersheds. Citing case studies throughout the region and ongoing research in the city of Bangalore, we demonstrate in-stream modifications may be capable of achieving significant improvement in the quality of urban wastewater and may play a complementary role in closing persistent capacity gaps in the operation of both centralized and decentralized treatment practices within megacities. Anticipating the larger diffusion of PGI practices across the region by various early adopters and non-state actors, we suggest a cogent research agenda focused on identifying various generalizable 'upscaling' opportunities for deploying in-stream interventions across various organizational and spatial domains.

Urbanisation and emerging economies: Issues and potential solutions for water and food security.

Urbanisation will be one of the 21st century's most transformative trends. By 2050, it will increase from 55% to 68%, more than doubling the urban population in South Asia and Sub-Saharan Africa. Urbanisation has multifarious (positive as well as negative) impacts on the wellbeing of humans and the environment. The 17 UN Sustainable Development Goals (SDGs) form the blueprint to achieve a sustainable future for all. Clean Water and Sanitation is a specific goal (SDG 6) within the suite of 17 interconnected goals. Here we provide an overview of some of the challenges that urbanisation poses in relation to SDG 6, especially in developing economies. Worldwide, several cities are on the verge of water crisis. Water distribution to informal settlements or slums in megacities (e.g. >50% population in the megacities of India) is essentially non-existent and limits access to adequate safe water supply. Besides due to poor sewer connectivity in the emerging economies, there is a heavy reliance on septic tanks, and other on-site sanitation (OSS) system and by 2030, 4.9 billion people are expected to rely on OSS. About 62-93% of the urban population in Vietnam, Sri Lanka, the Philippines and Indonesia rely on septic tanks, where septage treatment is rare. Globally, over 80% of wastewater is released to the environment without adequate treatment. About 11% of all irrigated croplands is irrigated with such untreated or poorly treated wastewater. In addition to acute and chronic health effects, this also results in significant pollution of often-limited surface and groundwater resources in Sub-Saharan Africa and Asia. Direct and indirect water reuse plays a key role in global water and food security. Here we offer several suggestions to mitigate water and food insecurity in emerging economies.

Assessing local materials for the treatment of wastewater in open drains.

In the present study, three low-cost filter aggregate materials were tested and compared for organic matter and fecal coliform (FC) removal at the laboratory scale. Setups were subjected to synthetic wastewater at two hydraulic loading rates (HLR), i.e. 4 cm/day and 40 cm/day. The hydraulic retention time (HRT) at the two HLRs varied from 4 days to 12 h, respectively. The result obtained shows that the biochemical oxygen demand (BOD5) removal efficiency of aggregate materials decreased with the increase in HLR. Both at high and low HLR, the terracotta aggregate material exhibited maximum BOD5 loading removal and without significant difference for the case of FC removal efficiency for all the three aggregate materials. At higher HLR, cell debris and biofilm loss from the aggregate material contributed to the chemical oxygen demand (COD) levels in the treated water. The terracotta aggregate material provided best organic matter removal at both HLRs. The study demonstrates the potential of incorporating inexpensive and readily available local materials into decentralized, frugal green infrastructure interventions capable of lowering the quantum of harmful biological contaminants in open storm water channels in rapidly urbanizing cities of developing countries, and that the terracotta aggregate material provided best organic removal at both HLRs.

Efficiency evaluation of sewage treatment plants with different technologies in Delhi (India).

Physical, chemical and microbiological efficiencies of Sewage Treatment Plants (STPs) located in Delhi's watershed in context of different treatment technologies employed in these plants have been determined. There were in all seventeen STPs treating domestic wastewater which were studied over a period of 12 months. These STPs were based on Conventional Activated sludge process (ASP), Extended aeration (Ex. Aeration), physical, chemical and biological removal treatment (BIOFORE) and oxidation pond treatment process. Results suggests that except "Mehrauli" STP which was based on Extended aeration process and "Oxidation pond", effluents from all other STPs exceeded FC standard of 10(3) MPN/100 ml for unrestricted irrigation criteria set by National river conservation directorate (NRCD). Actual integrated efficiency (IE(a)) of each STP was evaluated and compared with the standard integrated efficiency (IE(s)) based upon physical, biological and microbiological removal efficiencies depending upon influent sewage characteristics. The best results were obtained for STPs employing extended aeration, BIOFORE and oxidation pond treatment process thus can be safely used for irrigation purposes.