Wastewater treatment using Soil Biotechnology at Herohalli Lake

Several of the lakes in Bangalore face a common problem of inflow of sewage from neighboring communities into the lake. Though violating a law shying away from the ground reality wouldn't solve the problem in any way. Hence, a group of people which included citizens, developers, organizations from the Sarjapur/bellandur region of Bangalore, embarked on a visit to Herohalli Kere to understand the mechanisms of Soil Biotechnology which has been used to treat wastewater entering the lake. The below write up summarizes the observations made during the visit by the participants:

Lake description

The lake is spread across 25 acres. The jurisdiction of Herohalli Lake is with BBMP. In other words, the maintenance of the lake is the responsibility of BBMP. Couple of years back, the lake had completely dried up. Being a landlocked lake without any natural inflows or outflows, BBMP thought of piloting a solution. The plan was to restore the lake by diverting sewage from a major sewage channel into the lake, treat it in a local STP (Soil Biotechnology in this case) and then release the treated sewage into the lake. In this case, the technology for treating the sewage is called Soil Biotechnology which works on similar principles of sewage treatment yet in a different way.

The lake is surrounded by independent houses which means that their sewage is not treated by privately run STPs. Moreover, majority of sewage inflow is domestic. However, there are some polluting industries in the neighborhood, which release chemicals (dye, etc.) periodically (illegally!) into the sewage. At that time, the inlet sluice gate is closed to prevent the polluted sewage from entering the plant. The staff has to keep a constant watch on the incoming sewage.

Process description

The process is called soil biotechnology (SBT). The technology is developed in-house by IIT-Bombay researchers and been implemented at Herohalli through Vision earthcare.

According to the design engineer, the plant is designed for 1.5 MLD and works at approximately 70% capacity.

Components of the process/system:

1. Jackwell:

1.5 MLD sewage is pumped from Jackwell. A screen chamber separates materials like plastic, etc.

2. After initial pumping from Jackwell, the sewage passes through following chambers for further screening:

• Manual screen chamber
• Mechanized 10 mm screen chamber
• Grit chamber
• Oil layer skimming chamber

3. Primary sedimentation tank (PST)- Settling/Anaerobic/Hydrolysis reaction

Tank capacity 200 cu.m. 3-4 hours retention time.

4. Soil bioreactor:

Area: 50m*40m

Volume of bioreactor: 3000 cu.m

Water holding capacity: 300 cu.m

The plant has two SBT tanks of equal size, one of which is considered as secondary stage and the second tank is considered as the tertiary stage. The roles are reversed every 3 months.

The Soil bed consists of:

1. A thin layer of gravel at top (prevents soil erosion)
2. 1.25m deep active media in the middle, primarily made of crushed laterite rock, soil, and clay brick. The active media also contains bacterial culture. A large number of earthworms are released in this layer, which keep the layer aerated and feed on the biodegradable material to reduce it quickly.
3. 0.2 mm Jelly at the bottom (acts as filter media)

The water is pumped as follows:

1. Water coming from the primary filtering stage is pumped by 2x 5BHP pumps into the first SBT tank.
2. A grid of 2” CPVC pipes is laid on the top of the SBR tank, in which pipes are laid parallel to each other and 1m apart.
3. Each pipe has 8mm dia holes on its sides, 50 cm apart.
   
   Sewage pours out of these holes onto the gravel (top layer of the SBT tank). 
4. The sewage passes through the three layers, and reaches the bottom.
5. The tank bottom has a gentle slope towards the rear end of the plant. The water is collected at the back of the SBT tank, and again pumped to a second identical tank that is used as tertiary treatment stage.
6. According to the design engineer, the first tank treats the BOD/COD, and only then the second tank can treat the nitrates and phosphates.
7. Treated water from secondary treatment chamber collected in the recycling tank and diverted to tertiary treatment plant and finally let into the lake through 4” diameter pipes. Slope has been provided to do so.  

Total process time: approximately 12 hours

Approximately 3 ton of sludge is settled in primary sedimentation tank. In course of time the sludge which settles will be hydrolyzed and will dissolve in the water itself.

 

Discussion points:

Quality of treated sewage	Inlet BOD 250, OUtlet BOD 4. Outlet COD 37.3
Power requirement	3 Pumps, total 7 kw power
Land required	General rule: 1 sq.m per KLD. Possible to customize
Capital cost	2-3 cr
Operation and Maintenance costs	60-70 k per month operating fee, 6-7k electricity cost per month
Maintenance requirement	Cleaning of screens, removal of sludge, de-clogging of pipe holes
Operator attention	Throughout attention by operator needed. Checking the blocked holes of the pipe in the soil bioreactor, color of the incoming sewage as garment industries nearby
Reliability
Resource recovery	Sludge is recovered. Emptied on the soil bed itself. Plastic, paper recovered burnt here but can be recycled in other cases.
Ability to handle load fluctuations/seasonal changes
Chemicals/Industrial effluents	Inflow of garment industry, plant is switched off.

Questions:

Following are some of the questions (some have been responded) that would help evaluate the technology in a better way: 

1. BOD/COD and other water quality parameters after Primary sedimentation tank?

Typically about 70%-75% of incoming BOD/COD. However this is to be tested

2. Final output water quality all parameters? Especially nitrates and phosphates

Test report: https://drive.google.com/open?id=0B3Cww_NACAiDVkVjQTdRa2JaMVE&authuser=0

Nitrate and Phosphate data not available

3. Approved by KSPCB or not?

4. Existing sewage in the lake. What can be done?

Over a period of time, plan is to visit and understand few more technologies like conventional sewage treatment, phytorid, etc. 

Lake Bio-remediation meeting

BIOME, WIPRO, MAPSAS and other lakes communities have come together to try and understand how bio-remediation technologies can be applied to deal with the sewage inflow into some of the rejuvenated/to be rejuvenated lakes around Sarjapura Road.

Hence on 25^th November the first meeting was arranged to discuss bioremediation methods, to bring together the community working on different lakes in Bangalore on a same platform and decide on the further agenda for 15 lakes selected for the project was the objective of the meeting.

Following are the key points/deliberations happened during the meeting:

   A.     The lakes that have been narrowed down for this project are:

 

   B.     An initial discussion was led by Priya from MAPSAS who explained about the links between the lakes through kaluves and hence the importance of controlling the sewage entering in the lakes.

   C.     Mr. Vishwanath explained about viewing lakes as an ecosystem with space for biodiversity, treatment, recharge zones, etc. He cited example of Jakkur lake wherein a treated sewage water from BBMP maintained STP goes into a constructed wetland and then into the lake. He suggested that things that can be studied for lake should include percolation study, water balance, nitrate and phosphate removal, biodiversity, etc.

   D.    Some legal issues were also discussed:

1. Areas without BWSSB underground drainage network are not allowed to dispose of their sewage either with or without treatment. Zero discharge i.e. 100% reuse of wastewater generated within the premises
2. Areas with BWSSB underground drainage network are allowed to dispose of their sewage with at least secondary treatment 
3. The discharge standards for sewage treated water are close to drinking water standards

   E.     An important part of the meeting was presentations by vendors implementing bio-remediation technologies. Presentations were made by Visionearthcare on soil biotechnology (SBT), Hydrocreatives on Phytorid, and CDD on Decentralized wastewater treatment system (DEWATS).

  

Soil biotechnology (SBT): Have done for Herohalli Lake in Bangalore.

Their detailed presentation can be found http://www.slideshare.net/biomeshubha/sbt-for-lakes-bioremediation

a.     No external aeration is required as the different porous layers in the medium/bed help in aeration.

b.     One time media installation. No need to change soil media frequently

c.      No sludge formation

d.     Space: 1 sq.m/KLD

e.     No foul odor

f.       Have established 65 plants across India. Also experience in designing for lakes

g.      Not designed for removal of nitrates and phosphates specifically yet it works in their removal

h.     Herohalli plant details: Design capacity-1.4 MLD, Area- 1650 sq. m, cost- 3 crores, power consumption-125 units/day

Phytorid technology

Their detailed presentation can be found here: http://www.slideshare.net/biomeshubha/phytorid-for-bioremediation-of-lakes

a.     Plants have been designed particularly for BOD reduction and some amount of COD reduction also happens

b.     Power Cost: Rs. 1/KL

c.      Sedimentation tank: needs to be cleaned once in a year

d.     Issues with phytorid bed: Plants grow over a period and hence need to be cut as suited by the community. The disposal of cut plants is similar to other plants.

e.     No foul odor as water is not seen from above, no exposure

f.       Bacterial addition: once in a lifetime of the plant

g.      Space: for sedimentation tank/underground primary settling tank- 0.2/0.3 sq.m/KL and for phytorid bed- 0.9 sq.m/kl

h.     Cost per MLD: 1.3 crores

i.       Sensor based system

j.       Capacity range: 3 KLD -1.5 MLD

k.      The system needs to be placed in open as it needs sunlight for the plants to grow

l.       Water load fluctuation: the plants can survive without water (especially this may happen in dry season) for two months. Even if little amount of water is available, the plants can survive on fewer nutrients.

m.   If slope/gradient is available then no pumping is required

Decentralized wastewater treatment system (DEWATS):

Their detailed presentation is available here: http://www.slideshare.net/biomeshubha/how-dewats-can-be-implemented-to-bioremediate-lakes

a.     Shared case study of Bandhwa Talab in Raipur, Chattisgarh.

b.     This system based on phytotechnology which uses Canna indica plant which has shallow fibrous root system

c.      No color, odor and pathogens after passing the water through the bed of plant

d.     Based on requirement design can be customized

e.     The flow should be checked daily, sludge removal from the settling tank (primary treatment) is also required

f.       Treats only organic waste, domestic sewage

g.      Cost varies with capacity

   F.      Further deliberations and studies are needed on:

1.     Assuming that some amount of sewage already exists within the lakes, which of the systems would be useful?

2.     It is essential to conduct water balance study for every lake. Water balance means, calculating percentage of water coming, sewage coming, water percolating, evaporation, etc.

3.     Understanding the suitability of the system based on cost, maintenance, power consumption and mostly its ability to handle water load fluctuation, etc.

Based on primary data collection from each of the implemented technologies, water balance for some of the lakes and finally deliberations on bio-remediation technologies would help in seeking most suitable method to tackle the issue at hand.

We would like to thank the participants:

Vendors: Sharan Kumar from Visionearthcare for SBT, Mr. Himanshu from Hydrocreatives for Phytorid, Mr. Andrew Jacobs from CDD for DEWATS

Devarabisanahalli lake/Adarsh residents

Halanayakanahalli lake group

Priya representing MAPSAS

WIPRO

Students from Christ University

RWH in Vivek Khanna's home, Shubh Enclave, Haralur Road

Vivek Khanna at Kasavanahalli kere

Rainwater Harvesting was implemented in Vivek Khanna's residence in Shubh Enclave in early 2009.  The system comprised storage of rooftop rainwater in a large 15,000 liter sump as well as 2 recharge wells of 5ft diameter and 30ft depth. 

A chance encounter with Vivek Khanna at Kasavanahalli lake today revealed that his sump fills up with water every time it rains reducing his dependence on ground water. His recharge wells have not only kept his borewell running but also resulted in water in the newly dug borewells of his downstream neighbours (probably because of the recharge) where as some of the other newly dug borewells in the layout do not yield !! His new neighbours are now interested in getting RWH implemented in their homes

Recharge Well - just completed in 2009

Each of these stories reiterates the benefits of rainwater harvesting - both storage and recharge. Many thanks to him for sharing this story with us

The relationships between the recharge wells in his home as well as the nearby borewells would also be good cases to study as part of the aquifer mapping project

Newly constructed recharge well in 2009

Underground RWH filter construction in progress

Biome attends the WEDC International Conference to present research from the Resource Recovery and Reuse Project

Since April 2014, Biome has been working on a multidisciplinary research initiative funded by the Swiss Development Corporation (SDC) lead by an international partnership of organizations that includes the International Water Management Institute (IWMI), the World Health Organization (WHO), the Swiss Tropical and Public Health Institute (STPHI) and Sandec (Department of Water and Sanitation in Developing Countries) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag).

The ‘Resource Recovery and Reuse: From Research to Implementation Project’ aims to find enterprises and business models that have demonstrated their capacity for the safe reuse of waste, and to find ways in which these business models can be adopted or scaled up within their own setting or in other regions. The funding partner, SDC, has indicated that it would be inclined towards funding some of the scaling up activities after the research is completed. The project currently runs in four cities, Kampala, Lima, Hanoi and Bangalore with the aim that lessons can be shared across different contexts. Biome leads the institutional component of the research in Bangalore (the other components are lead by other partners that include the Community Health Department at St. Johns Hospital, IISc and Waste Wise Trust). This involves understanding both the larger environment around which activities and businesses that work with waste have arisen as well as the more localised conditions that influence the way institutions operate and function. Together with partners[1], our work has involved selecting a small number of interesting cases that demonstrate safe reuse and in order to understand how they function. Research was conducted primarily through interviews with the most important government agencies that deal with waste and wastewater, businesses that are at the centre of this work, and desk based study on the larger context of solid waste and wastewater management in the city.

 In September, a short paper based on the research conducted for the project was presented at the 37^th WEDC International Conference held in Hanoi, Vietnam. The conference has a long history with a strong focus on presenting the work of practitioners from the WASH sector working in developing countries and this year’s theme was ‘Sustainable Water and Sanitation Services for all in a Changing World’.

The paper, titled ‘Formal Approaches to Wastewater reuse in Bangalore’ was presented at the session on Sanitation Institutions and looked at the different approaches taken by the BWSSB and the KSPCB with regards to wastewater. It presents the contrasting perspectives of the utility and the regulator - the former’s concern with managing wastewater infrastructure and its approach of taking delicate steps towards expanding public treatment and reuse, while the latter’s challenge in regulating pollution and monitoring the city’s large number of private treatment plants. 

This is the first of three posts that will discuss the research and findings of the institutional component of the RRR project, whose first phase ends in December this year. 

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[1] Acknowledgments to Alexandra Evans (Loughborough University) and our research partners at IWMI with whom we have worked closely on this project.

Borewell pump test at SJR Verity

Yesterday (Nov 9, 2014), ACWADAM and Biome performed a pump test on one of the yielding borewells in SJR Verity which is located in Kasavanahalli road. This borewell is generally switched on for a period of 3 hours and switched off for 3 hours and then again the cycle restarts.

We started the test at around 830 AM by switching on the borewell and also measuring the static water level (distance between ground level and water level in the borewell). This level was around 17.5 m during the start of the pump test. We measured the yield or discharge rate of the borewell by catching the water falling in the sump in a 15 litre bucket and measuring the time taken for the same. Since we did not have a stop watch in both our mobile phones, played a song and stopped once the bucket got full to measure the time taken in minutes and seconds. The discharge rate came out to be 762 litres per hour. Subsequently, we kept measuring the static water level at every 5 minute interval and then at every 10 minute interval from the 40th minute. The discharge rate was again measured at the 90 minute and 150 minute mark respectively and it came out to be 692 litres per hour both times. The static water level stabilized at 19.4 m and we measured the levels till the 160th minute. Since the levels stabilized, we did not measure for 180 minutes.
For the recovery part, the borewell motor was switched off and then the rise in water levels was monitored. This rise was documented every 5 minutes for the first 40 minutes and then at a 10 minute interval. The rise stabilized at around the 16 m level and we recorded readings till the 150th minute mark.

Similar data collected from the other borewells would help us in getting a deeper understanding of the aquifer.

Thanks to SJR Verity residents for all the coordination.