Lakes and water bodies also referred to as wetlands are one of the most productive ecosystems contributing to ecological sustainability thereby providing necessary linkages between land and water resources. The quality and hydrologic regime of these lakes and wetlands is directly dependent on the integrity of its watershed. In last couple of decades, rapid urbanization coupled with the unplanned anthropogenic activities has altered the wetland ecosystem severely across globe. Changes in land use and land cover (LULC) in the wetland catchments influence the water yield and water quality for the lakes. Apart from LULC changes, the inflow of untreated domestic wastewater, industrial effluents, dumping of solid wastes and rampant encroachments of catchment has threatened the sustenance of urban wetlands. This is evident from the nutrient enrichment and consequent profuse growth of macrophytes, impairing the functional abilities of the wetlands. Reduced treatment capabilities of the wetlands have led to the decline of native biodiversity, prevailing unhygienic conditions with mosquito menace, contamination of groundwater levels, affecting the livelihood of wetland dependent population. Decline in the services and goods of wetland ecosystems have influenced the social, cultural and ecological spaces as well as of water management. This necessitates a systematic lake rejuvenation paradigm and associated monitoring of wetlands to mitigate the impacts through appropriate management strategies. A combination of LULC analysis in the catchment using remote sensing data acquired through the space-borne sensors facilitates identification of valley zones and wetland area. This in turn aids in maintaining records for encroachment and consequent action. Factor like nature of the catchment, wastewater quality and quantity influx, garbage dumping etc. related to water quality are the most important pressure driving the productivity of these rapidly disappearing wetland systems and are reasons for today’s dominance of exotic organisms with increasing heterogeneity of biotic components at an intermediate spatial and temporal scale. Nutrient (C, N and P) influx being the most significant reason for the present deterioration of these wetland and water bodies. Suitable catchment management practices with strategic control of untreated industrial and domestic effluents getting into these water bodies will be key for a sustainable city management plan. Recommended de-silting and de-weeding the water bodies, complete treatment of municipal and industrial wastewater, a ban in P use in detergents, removal of encroachments, fencing and green belt around the water bodies, and growth of essential N-rich aquatic vegetation for the livelihood of nearby dependent communities and provision to retain the natural floating islands for in-situ bioremediation. Further strategic planning needs to be adopted at the higher level for increase in consensus for optimal water usage, provisions for rain water harvesting, ground water recharge etc. for fostering sustainable city management.

Vrishabhavathi Valley: Vrishabhavathi Valley is one of the three major valleys in Bengaluru, that flows south, joining Arkavathi, a tributary of river Cauvery. The catchment of V.Valley is nearly 170 sq.km covering about 90 Wards in BBMP. The catchment has about 70 lakes during the early 1970’s which has now reduced to ~35 as on 2017. Most of the lakes have been filled and converted into residential/industrial areas, the streams/rajakauveys are narrowed by dumping construction debris, solid wastes there by increasing instances of floods, mortalities in monsoons. Current population in V.Valley (2017) is about 40 lakhs with water demand of 596 MLD (150 lpcd). V.Valley generates about 480 MLD (2017) of domestic sewage which is expected to reach 544 MLD by 2021with the current growth rate before it exits the BBMP limits. The valley has current treatment capability of 265 MLD (working) and 80 MLD (under construction) which is insufficient to treat the domestic waste.
Major watersheds of V.Valley are (i) Vrishabhavathi valley, (ii) Katriguppe Valley (joins V.Valley at Rajarajeshwari nagar, before STP), (iii) Nagarabhavi Valley (joins V.Valley at Bangalore University Gate) (iv) Channasandara Valley (joins V.Valley behind RVCE/Global Village techpark, Rajarajeshwari nagar), (v) Sonnenahalli valley (joins V Valley near Vidyapeetha-Kengeri). Details describing watersheds as in Table 1

Highlights:

• Origin - at Bull temple, a small hillock next to Dodda Ganapathi Temple in Basavanagudi, Bangalore South, due to which it is known as Vrishabhavathi river (Vrishabh meaning Bull).
• Number of watersheds: 7 major watersheds  in Vrishabhavathi valley;
• Number of lakes: 70 (in 1970’s), now 35 (in 2017) ; after swallowing by land mafia (50% disappeared lake)
• Domestic sewage: 480 MLD (2017) and expected to reach 596 MLD (2021)
• Serious threats:
• Encroachments (rampant in each lake – for example Prakashnagara / Balehannu kere and many such lakes),
• Sustained inflow of untreated sewage and industrial effluents, 
• nexus of senseless local politicians, bureaucrats, consultants and civil contractors [evident from narrowing and concretizing storm water drains, completely ignoring hydrological functions (groundwater recharge, bioremediation, mitigation of floods) of drains and also violating NGT guidelines on storm water drains and buffer regions].
• Health issues: Contaminated fodder, fish and vegetable (contamination of food chain) due to polluted water in the lake with untreated industrial effluents (containing heavy metals, etc.). Respiratory and cancer episodes with volatile organic compounds and aerosols in the air environment. Breeding of disease vectors and instances of Chikangunia, Dengu, etc.

Table 1: Current condition of V.Valley watersheds.

Recommendations:

Constructed Wetlands: The loss of ecologically sensitive wetlands is due to the uncoordinated pattern of urban growth happening in Bangalore. This is due to a lack of good governance and decentralized administration evident from a lack of coordination among many para-state agencies, which has led to unsustainable use of the land and other resources. Failure to deal with water as a finite resource is leading to the unnecessary destruction of lakes and marshes that provide us with water. This failure in turn is threatening all options for the survival and security of plants, animals, humans, etc.

There is an urgent need for:

• Restoring and conserving the actual source of water—the water cycle and the natural ecosystems that support it—are the basis for sustainable water management.
• Reducing the environmental degradation that is preventing in attaining the goals of good public health, food security, and better livelihoods.
• Improving the human quality of life that can be achieved in ways while maintaining and enhancing environmental quality.
• Reducing greenhouse gases to avoid the dangerous effects of climate change is an integral part of protecting freshwater resources and ecosystems.

A comprehensive approach to water resource management is needed to address the myriad water quality problems that exist today from nonpoint and point sources as well as from catchment degradation. Watershed-based planning and resource management is a strategy for more-effective rejuvenation, protection and restoration of aquatic ecosystems and for protection of human health. In this regard, recommendations to improve the situation of the lakes are:

• Decentralised treatment of sewage and solid waste (preferably at ward levels). Sewage generated in a locality /ward is treated locally and letting only treated sewage into the lake (Integrated wetlands ecosystem as in Jakkur lake). Integrated wetlands system consists of sewage treatment plant, constructed wetlands (with location specific macrophytes) and algal pond integrated with a lake. Constructed wetland aid in water purification (nutrient, heavy metal and xenobiotics removal) and flood control through physical, chemical, and biological processes. When sewage is released into an environment containing macrophytes and algae a series of actions takes place. Through contact with biofilms, plant roots and rhizomes processes like nitrification, ammonification and plant uptake will decrease the nutrient level (nitrate and phosphates) in wastewater.  Algae based lagoons treat wastewater by natural oxidative processes. Various zones in lagoons function equivalent to cascaded anaerobic lagoon, facultative aerated lagoons followed by maturation ponds. Microbes aid in the removal of nutrients and are influenced by wind, sunlight and other factors (Ramachandra et al., 2014). This model is working satisfactorily at Jakkur. The sewage treatment plant removes contaminants  (evident from lower COD  and BOD) and mineralises organic nutrients (NO3-N,  PO43- P)  to inorganic constituents. Integration of the conventional treatment system with wetlands [consisting of reed bed (with typha etc.) and algal pond] would help in the complete removal of nutrients in the cost effective way. Four to five days of residence time in the lake helps in the removal of pathogen apart from nutrients. However, this requires regular maintenance through harvesting macrophytes and algae (from algal ponds). Harvested algae would have energy value, which could be used for biofuel production. The combined activity of algae and macrophytes helps in the removal of  ~45% COD, ~66 % BOD, ~33 % NO3-N and ~40 % PO43- P.  Jakkur lake acts as the final level of treatment that removes ~32 % COD, ~23% BOD, ~ 0.3 %  NO3-N and ~34 % PO43- P.  The lake water with a nominal effort of sunlight exposure and filtration would provide potable water. Replication of this model in rapidly urbanizing landscapes (such as Bangalore, Delhi, etc.) would help in meeting the water demand and also mitigating water scarcity through recharging of groundwater sources with remediation.

• Better regulatory mechanisms such as
• To make land grabbing a cognizable, non bailable offence
• Implementation of the polluter pay principle
• Ban on construction activities in the valley zones
• Restriction of diversion of the lakes for any other purposes
• Decentralised treatment of sewage and solid waste and restriction for entry of untreated sewage into the lakes
• Encouraging involvement of local communities: Decentralised management of lakes through involvement of local communities in the formation of local lake committees involving all stakeholders.

Taking advantage of remediation capability of aquatic plants (emergent macrophytes, free floating macrophytes) and algae, constructed wetlands have been designed and implemented successfully for efficient removal of nutrients (N, P, heavy metals, etc.). Different types of constructed wetlands (sub surface  0.6 m depth, surface: 0.4 m, could be either horizontal or vertical) are given in Figure 1. Area required for constructed wetlands depends on the influent sewage quality and expected treatment (BOD removal, etc) is given in equation 1 (Vymazal et.al, 1998). Estimates show that to treat 1 MLD influent, area required is about 1.7 hectares. Figure 2 gives the design of wetlands to treat 1 MLD.

A = Qd(lnCo – lnCt) / KBOD
where  A = area; Qd= ave flow (m3/day); Co & Ct = influent & effluent BOD (mg/L);   KBOD = 0.10

For example to treat influent (raw sewage: BOD: 60-80) and anticipated effluent (with BOD 10), area required is about 1.7 to 2 hectares. Table 1 lists bioremediation potential of macrophytes.

Table 1: Nutrient and heavy metal removal by Macrophytes

Quantities of elements that could be removed by continual culture of some aquatic plants (kg/ha/year) ( Reference:handbook of utilization of aquatic plants,FAO, http://www.fao.org/docrep/003/x6862e/X6862E11.htm)

RESTRICT PHOSPHATE BASED DETERGENTS IN INDIA
To mitigate Foaming or Algal Bloom in Water bodies of India

Source: Ramachandra T V, Durga Madhab Mahapatra, Asulabha K S, Sincy Varghese, 2017. Foaming or Algal Bloom in Water bodies of India: Remedial Measures - Restrict Phosphate (P) based Detergents,  ENVIS Technical Report 108, Environmental Information System,  CES, Indian Institute of Science, Bangalore 560012

Surface Aeration for Lakes  to increase the dissolved oxygen levels in the water body.

The wastewater treatment bioprocesses transform minute solids and dissolved organic matter present in wastewaters into organic and inorganic solids that can be settled by application of flocculants.
Process analysis:

• Microbes as bacteria – transforms particulate carbonaceous colloidal matter and dissolved organics present in wastewater into bulkier cellular lumps/tissues and into gases as a metabolic by product.
• The gases escape into the environment
• The cellular masses are removed with the help of sedimentation tanks or clarifiers.
• The main objectives of Bio-treatments are to reduce organic matter in wastewaters mainly measured in the form of BOD, COD and TOC.
• Bio-treatments also remove nutrients (N and P) from wastewaters.
• These bioprocesses are used in tandem with other physico-chemical processes for attaining optimal effluent quality.
• Bio-processes technologies used in wastewater treatment can be broadly divided into three categories – Aerobic, Anaerobic and Anoxic
• These processes can be run either as suspended growth system or attached growth system or as a combination of both.

Working of Conventional Wastewater Treatment Systems: The conventional treatment set up for wastewaters comprise of primary, secondary and tertiary treatments (Table 3) that involves various steps

Screening is essentially to remove larger floating solids that take a very long tome for breakdown and decomposition. The screen comprises of an ordered array of flat metal plates that are welded to the horizontal bars at ~ 4 cm – 2 cm spacing. During the course of the water flow, the screens are juxtaposed perpendicular to the flow direction. The large amount of floating materials, sand debris, polymers etc stuck to the screen is removed manually or through other mechanical means. These floatable materials are then carried out as solid waste for proper disposal.

The grit removal process mainly intends to remove heavy and inert inorganic matter. Grit, dense coarse materials, sand, shells, gravel and other heavy inorganic matter tend to settle by sedimentation in the settling basin within a minute. The materials are then send to proper disposal sites.

The primary clarification happens in a settling basin that is intended for settling of heavier inorganic matter. These clarifiers have detention period of ~ 120 minutes and are mostly circular in shape. The settled materials on various parts of the clarifiers are scraped and pushed towards the centre with the help of rakers and the settled material mostly known as primary sludge are then transported to the through the primary sludge pump to the sludge digesters. Importantly in this exercise ~40 % of BOD and ~70 % of suspended solids are removed.

Secondary treatment involving suspended aerobic processes in carried out with the help of aerobic microbes. At this stage, the wastewater are mostly devoid of particulate inorganic and organic matter and comprise of decomposed or semi-decomposed organic matter i.e. carbohydrates, proteins, lipids, fibres etc., in the presence of oxygen and aerobic bacteria these compounds are broken down into simpler forms as carbon dioxide, ammonia, water etc. The microbial activity transforms these dissolved forms into flocculating biomass and the finer organic matter into settleable mass. The oxygen is provisioned through the help of surface aerators that helps in the growth of aerobic bacteria that are required for the decomposition of organic matter. The powerful surface aerators droves the wastewater through a mechanical churning process from the bottom of the aeration tank units and splatters it over the surface thus ensuring oxygenation mobilisation.

Secondary treatment involving attached growth processes involves of wastewater over a combination of media that acts as substrates for attachment and growth of microbes over the surfaces. In this biological process the surface grown biological microbial assembly absorbs the organic matter the wastewaters and starts multiplying of the surface of the substrates. When the weight of the surface biomass becomes critical is swept away by the trickling waters that captured in the subsequent settling units and are often recycled back. Various types of media can be used for development of the attached microbial communities as gravel, pebbles; granite of ~10-15 cm is often used in trickling filters.

The final round of settling the solids is performed by the secondary clarifiers where the microbial flocks comprising of cellular biomass and organic aggregates are made to settle. Usually these settling clarifiers are circular in shape and with a retention time of ~90-120 min. The same rakers are used to draw the settled sludge to the centre which is then carried for recirculation to the aerobic tanks or the trickling filters. The excess amount of the solid/sludge is transferred to the sludge thickeners that separate the excess water content in the sludge. This biological process ensures ~90% of BOD removal and ~90% of SS removal of the influent wastewater.

Table 3: Various wastewater treatment and process parameters

    
WWT Technologies working at Bangalore are

• ASP (Activated Sludge Process)
• EA (Extended Aeration)
• TF (Trickling Filters)
• UASB (Up-flow Anaerobic Sludge Blanket Reactor)
• SBR (Sequential Batch Reactor)
• MBR (Membrane Bio-Reactor)
• MBBR (Moving Bed Biofilm Reactor)
• CAB (Cascading Algal Bioreactor)

Comparative assessment of wastewater treatment process are given in Table 4.

Table: 4: Comparative assessment of wastewater treatment process

VI	Membrane Bio Reactor (MBR)
1	Treatment Process: Membrane Bio Reactor (MBR)
2	Sketch
3	Technical details and Operation A membrane bioreactor functions with a coupled activity of membrane filtration with a biological active sludge system. Such systems help in replacement of the sedimentation basin as observed in classical biological purification and aids in separation of sludge from the effluent. This helps to ensure that all floating matter is retained, whereby sedimentation is no longer a restrictive factor for sludge concentration.  A membrane reactor is thus able to process significantly higher sludge concentrations (10-20 g/l) with a lower reactor volume, compared to conventional systems. The membrane can either be placed next to the biological basin (1. External or separate system), or in the basin (2. Internal or submerged). External systems involve continuous cross-flow circulation along the membranes. Both tubular and flat plate membranes are used to realise this. An internal system involves the effluent being extracted from the active sludge using under-pressure. This normally involves the use of hollow fibres or flat plate membranes. Micro and ultra filtration membranes are used for both types of MBR. Land Area requirement: 0.45 Ha/MLD (No Tertiary Treatment required) Power requirement: 302 kWh/d/MLD
4	Feasibility Membrane reactors are have been used throughout the world, for industrial as well as municipal wastewaters now. Membrane bioreactors can be used for biologically degradable wastewater flows as municipality wastewaters. The quality of the MBR permeate is greatly determined by the quality of the influent. Disruptive substances (e.g. long fibres or sharp particles) that can block or damage the membrane must be removed before wastewater is added to the MBR. Undissolved matter can normally be sufficiently removed using a simple sieve (gauze width 0.5 - 2 mm). Dissolved substances, primarily high calcium contents and aluminium salts, can also cause damage to the membranes. Specific toxic partial flows from, the chemical industry are not suitable unless sufficiently diluted with other process effluents. Excess sludge is produced as a by-product and necessitates from the system on a regular basis. The cleaning fluids also need to be disposed of. AOX could form if cleaning is carried out using NaOCl. Pure oxygen (O2) can be used to introduce sufficient oxygen into the MBR. This will result in fewer problems with foam and odour-forming.The MBR combines a biological wastewater purification system with a physical process, which increases the complexity. Both steps require specific attention to process execution and optimisation of control parameters. Full-scale MBR systems are normally thoroughly automated. Close follow-up is needed to allow the process to run correctly.
5	Economics: Infrastructure/Capital Cost: Rs. 30 million/MLD OM Cost: Rs. 1.2 lakhs/MLD/Y Running cost: >2 paise/litre
6	Suitability in the present context: Suitable but can only used at decentralised levels

Figure 3 provides comparative account of performance of various wastewater treatment options. Table 5 lists the treatment efficiency and area requirement for WWTP, while Table 6 lists the relative advantages of various treatment technologies and Table 7 gives the comparative assessment of  capital and OM Cost. Proposed wastewater treatment set-up for sewage influx is given in Figures 4 and 5 respectively.

Table 5: Treatment efficiency and area requirement for WWTP

Table 6: Relative advantages of various treatment technologies

Table 7: Capital and OM Cost

Figure  3: A comparative account of treatment performance of the WWT technologies

Figure 4: Proposed wastewater treatment set-up for lakes in V. Valley

Figure 5: Proposed wastewater treatment set-up for downstream lakes receiving partially treated sewage