FIELD INSIGHTS INTO BIOME’S WORK

Date: 04/08/2024

Members visited: Rajani, Bhavani, Amulya, Ruchitha, Ruthu, Trisha and Taabish.

We had the opportunity to embark on a fascinating field visit to Devanahalli Sihineerukere lake, open well in Hunasamaranahalli and rainwater harvesting at Sonnappanahalli Government School. This journey not only offered a glimpse into an essential water resource but also provided valuable insights into the complexities of water management practices.

During the visit, we met 26 students and 4 leaders from the TYCIA Foundation who had travelled to Bangalore as part of their Leadership Program, focusing on Bengaluru’s water situation and conservation efforts. The students who participated were from countries such as South Africa, the USA, Nepal, Lebanon, and Madagascar. The visit was expertly coordinated by Bhavani and Rajani from Biome Environmental Trust.

About TYCIA

Turn Your Concern Into Action (TYCIA) Foundation is a not-for-profit organization founded in 2011. It adopts a holistic approach to creating meaningful change, focusing on marginalized and often overlooked communities. TYCIA's initiatives range from training programs for tribal farmers to customized educational solutions for incarcerated youth. Through these efforts, the foundation is dedicated to empowering vulnerable sections of society by providing equitable, quality opportunities to bridge social inequalities.

Sihineerukere Lake, Devanahalli

An open well is a basic hole in the ground that provides access to underground water. These wells draw water from the shallowest level in the area, usually found in unconfined shallow aquifers. These aquifers are layers of soil or rock close to the surface where water is stored without pressure. Shallow aquifers are replenished when rain or surface water percolates down into them, a process known as recharge. The water levels in these aquifers can rise and fall depending on how much water flows in or out.

Lakes in Bengaluru, once the main source of drinking water, now receive 2.1 million liters per day (MLD) of treated wastewater from Bengaluru, which is pumped into several lakes in Devanahalli, including Sihineerukere, through the HN Valley Project. An open well next to the lake, with a depth of 30 feet, receives natural water and has the potential to yield up to 1.5 lakh litres of water daily.

What we learned about

Rain Gauge
A rain gauge is a tool used to measure how much rain falls over a certain period. It typically consists of a cylindrical container with a funnel that directs the rain into a measuring tube. The amount of collected rainwater is then measured in millimetres or inches, providing an accurate reading of precipitation levels.

TDS (Total Dissolved Solids)
A TDS meter measures the amount of dissolved solids in water. These solids can include salts, minerals, and organic matter.

UV Disinfectant Tank
A UV disinfectant tank uses ultraviolet (UV) light to purify water by killing or inactivating microorganisms such as bacteria, viruses, and protozoa. UV disinfection is an effective and chemical-free method of treating water.

How it works: Water enters the UV disinfectant tank and passes through a chamber that houses the UV light source. As the water flows through the chamber, it is exposed to UV light at a specific wavelength (typically 254 nanometres), which penetrates the cells of microorganisms, effectively inactivating them.

Hunasamaranahalli open well 

Our next stop was at the Hunasamaranahalli Open Well, located opposite the Academy of Aviation and Engineering. Hunasamaranahalli, located 22 kilometres from Bengaluru, is a small town within the Yelahanka taluk of the Bengaluru Urban District in Karnataka. The Hunasamaranahalli Town Municipal Council (TMC) was established on March 26, 2021, by merging the gram panchayats of Hunasamaranahalli and Sonnappanahalli.

(image source: urbanwaters)

This well, originally dug by a farmer 70-80 years ago to irrigate agricultural fields, has a diameter of 24 feet and a depth of 60 feet. Initially, the well's stone lining was only at the bottom 20 feet and the top 13 feet, starting from the parapet level. In the past 5-6 years, improvements were made, including clearing vegetation by the nearby Legend Hill View Apartment and repair work by Hotel Arna. The parapet wall was repaired, and the stone lining was extended an additional 10 feet in depth and also was beautified by warli art. This well now provides approximately 1.5 lakh litres of water daily to the TMC, which pumps it to a sump tank near the Sonnappanahalli Panchayat office for distribution to areas such as Shaktinagar, Muneshwar Camp, and nearby wards.

Rainwater harvesting at Sonnappanahalli Govt School

Our final visit was to the government school at Sonnappanahalli, which has a student capacity of 350 and a daily water demand of 5,000 litres. Under ITC Limited’s CSR initiative, a rainwater harvesting setup was implemented to create a sustainable water conservation model for the surrounding community.

Rainwater Harvesting System
Rooftop runoff is collected through 4-inch diameter pipelines, with the initial runoff being deposited directly into the ground using a manual valve. A Y-joint prevents debris from entering the filter, which diverts water into a reject pipe. The remaining rainwater is collected in a harvesting pit layered with larger stones, charcoal, and smaller aggregates. The setup’s underground sump is designed to accommodate 12,000 litres. It is 20 feet deep and 4 feet in diameter, with capacity based on the region’s average rainfall.

The school’s backyard well, which supplies 50,000 litres daily after rejuvenation, has been polluted by contaminants from nearby neighbourhood soak pits.

The Anganwadi buildings, located beside the school, were also modified with sloped terraces and a parapet wall to prevent rainwater from flowing across the building's external walls. This modification helps prevent prolonged exposure to water and allows for rainwater collection. Additionally, taps in the school were fitted with aerators to regulate water usage.

(Image source: urbanwaters)

Key Learnings

• Groundwater Recharge helps contribute to the replenishment of groundwater levels when managed properly, allowing rainwater to percolate and recharge the aquifer.
• There is great environmental impact using rainwater reduces the demand on traditional water sources, supports sustainable water use, and helps manage stormwater runoff, reducing the risk of flooding and erosion.
• Community participation in rainwater harvesting systems can be implemented at individual, community, or institutional levels, promoting water conservation and increasing local water availability.

Written by:

Amulya S

Ruchitha Singh B

Ruthu M

How is wastewater treated? Exploring a Sewage Treatment Plant.

Date of visit: 29/07/2024

Members visited: Deeksha, Ayushi, Apeksha, Nikita, Neelima, Avinash, Krishna, Taabish, Trisha, Amulya, Ruchitha and Ruthu.

As Bachelors of Planning students interning at Biome, we recently had the opportunity to visit one of the Sewage Treatment Plant (STP) in Bengaluru on July 29, 2024, which has a treatment capacity of 40 million liters per day (MLD). The visit provided us with valuable insights into the complex and essential process of treating sewage. Upon our arrival at the plant, we were welcomed by a knowledgeable staff member who guided us through the treatment process, focusing on the activated sludge process (ASP). This process is crucial for removing contaminants from the sewage and making the water safe for discharge or reuse.

What is an STP?

As per CPHEEO manual, 80% of water supply may be expected to reach the sewers. Sewage treatment plant (STP) treats sewage or wastewater generated from domestic, industrial, or commercial sources to remove contaminants and produce treated effluent that is safe for discharge or reuse. 

Three stages of sewage treatment are:

PRIMARY TREATMENT	SECONDARY TREATMENT	TERTIARY TREATMENT
Primary treatment: It consists of removal of large suspended organic solids. It is usually accomplished by sedimentation settling basins. The liquid effluent from primary treatment typically contains a significant amount of suspended organic material.	Secondary treatment: Here the effluent from primary treatment is treated through biological decomposition of organic matter which is carried out either by anaerobic or aerobic conditions.	Tertiary treatment: The purpose of tertiary treatment is to provide a final treatment stage to further improve the quality of the effluent, before being discharged to the receiving environment. (Tertiary treatment is not performed at the STP we visited).

Sewage treatment plant technologies:

• Activated Sludge Process (ASP) 

• Sequential Batch Reactor (SBR) 

• Membrane Bio Reactor (MBR) 

• Moving Bed Bio Reactor (MBBR) / Fluidized Aerobic Bed rector (FAB)

(Source: KSPCB)

Treatment Process at STP

1. Pumping and Screening: The journey of sewage treatment begins with the raw sewage being pumped from the canal to the inlet chamber. The inlet chamber, equipped with three screen channels with the size of 25mm each, removes large debris such as wood, rocks, plastics, papers, and even dead animals. This step is vital to prevent damage to downstream equipment and ensure smooth operation.

2. Grit Removal and Organic Matter Separation: After screening, the sewage passes through a grit classifier, where sand and other fine particles are removed. In the grit classifier, organic matter is effectively removed using a centrifugal pump. This pump helps separate heavier particles and organic matter from the wastewater.

3. Conveyor plate: The next stage involves the removal of oil and grease-like substances using a conveyor plate. This marks the end of the primary treatment phase, where solid particles are effectively removed.

4. Anaerobic Zone: In the anaerobic zone, sewage sludge undergoes methane fermentation, facilitating the decomposition of macromolecular organic matter into simpler compounds. This biological process also helps in the removal of phosphorus content without the need for chemical additives.

Phosphorus is accumulated in the sludge and subsequently removed through sedimentation. The organisms responsible for this process, known as polyphosphate-accumulating organisms (PAOs), store phosphorus by building up reserves of polyphosphate.

PAOs break down internally stored polyphosphate to generate energy for the uptake of volatile fatty acids (VFAs) like acetate. This process results in the release of orthophosphate (PO₄³⁻) into the surrounding water.

5. Anoxic Zone: The anoxic zone plays a crucial role in the biological removal of nitrogen contents. The anoxic tank facilitates the process of denitrification, where nitrates (NO3) are reduced to nitrites (NO2) and potentially further reduced to nitrogen gas (N2), reducing the nitrogen content in the wastewater. 

Denitrification is a process where nitrates (NO₃⁻) are reduced to gaseous nitrogen (N₂) by facultative anaerobes, such as certain fungi. These organisms thrive in anoxic conditions by breaking down oxygen-containing compounds like nitrates to obtain oxygen. In aquatic environments, nitrogen is present in multiple forms, including dissolved nitrogen gas (N₂), ammonia (NH₄⁺ and NH₃), nitrite (NO₂⁻), nitrate (NO₃⁻), and organic nitrogen, which can exist as proteinaceous matter or in dissolved or particulate phases.

6 NO3- + 5 CH3OH → 5 CO2 + 3 N2 + 7 H2O + 6 OH-

6. Aeration Basin: The sewage then moves to the aeration basin, where oxygen is added to support the growth of aerobic bacteria. These bacteria further break down organic matter. A mixed liquor recycle pump recirculates a portion of the sewage back to the anoxic zone to enhance the denitrification process. After aeration, both Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are significantly reduced. This process enhances the degradation of organic pollutants, leading to clearer and cleaner effluent.

The BOD value is the amount of oxygen, dissolved in water, that is consumed by aerobic bacteria that degrade a certain amount of organic material in the wastewater.

The COD value indicates the amount of oxygen required to chemically oxidize the totality of organic matter in the wastewater.

An extended aeration process is used, where wastewater remains in the aeration tank for an extended period, typically 24 hours. This allows for more complete degradation of organic material, further reducing both BOD and COD levels.

As in the activated sludge treatment process, microorganisms, including bacteria, are used to degrade and consume the organic matter present in wastewater. Here the wastewater is mixed with a combination of these microorganisms, referred to as "mixed liquor."

As the microorganisms feed on the organic pollutants in the wastewater, they metabolize this organic matter, breaking it down into simpler substances like carbon dioxide (CO₂) and water (H₂O). During this process, the microorganisms require and consume dissolved oxygen, which is supplied by aerating the tank. The aeration ensures that there is enough oxygen available for the microorganisms to thrive and efficiently degrade the organic waste

Standards to maintained as per CPCB

pH	6.5-8.5
E. coli	500 MPN/100 mL
COD	250 mg/L
BOD	30-50 mg/L

7. Secondary Classifier: The remaining mixture proceeds to the secondary classifier, where sludge and water are separated. The secondary classifier is crucial as it helps in the removal of fine particles and residual solids from the wastewater after primary and secondary treatments. This step ensures the quality of treated water before further processes or discharge.

8. Chlorination: The final step in the treatment process involves disinfection. The treated water, now referred to as effluent, is passed through a chlorine contact tank, where chlorine is added to kill any remaining bacteria. The chlorine is neutralized, if necessary, before the water is discharged to the minor irrigation department for further use. 

The water, after undergoing secondary treatment, is tested for various parameters such as pH, COD, BOD, and E. coli etc. as per CPCB standards and are tested before being sent to Minor irrigation department. The data represents the monthly average of the recorded values.

LEARNINGS FROM THE VISIT

• We gained a deeper understanding of the Activated Sludge Process, which is a core treatment method used in the plant and various stages involved in the process i.e., screening, removal, anaerobic, anoxic and aerobic conditions, secondary classifier and chlorination.

• Difference between the anaerobic and anoxic zones with their respective functions. Even though both the processes take place in absence of oxygen, the nutrient removed in each process is different. Anaerobic zone plays a vital role in removing phosphorus content from wastewater while anoxic zone removes all the nitrogen contents. Contributing to pollution reduction. 

• Knowledge on extended aeration process, as the process in aeration zone takes place for 24 hours and significance of reducing BOD and COD in wastewater treatment while maintaining standards as per CPCB.

• Continuous monitoring, regular testing, and thorough data analysis are crucial for optimizing the treatment process and maintaining high standards of quality control. These practices help to identify and address any issues promptly, ensuring that the treatment plant operates efficiently and does not lead to any negative impacts on the environment or public health.

CONCLUSION

The field visit to the Sewage Treatment Plant was an enlightening experience. It underscored the complexity and importance of modern sewage treatment processes. We gained a deeper understanding of the necessity of investing in and maintaining robust water infrastructure. Furthermore, the visit highlighted the need for continuous research and innovation to enhance the efficiency and effectiveness of water treatment systems. This experience has deepened our appreciation for the critical role that such facilities play in sewage treatment infrastructure, safeguarding public health and the environment.

APPENDIX A: Detailed reactions 

In the first step of nitrification, ammonia is oxidized to nitrite by ammonia-oxidizing bacteria according to the following equation:

NH3 + O2 → NO2– + 3H++ 2e–

In the second step, nitrite is further oxidized to nitrate by nitrite-oxidizing bacteria according to the following equation:

O2– + H2O → NO3– + 2H+ +2e–

The energy reactions involved in this process can be illustrated as follows:

6 NO3- + 2 CH3OH → 6 NO2- + 2 CO2 + 4 H2O (Step 1)

6 NO2- + 3 CH3OH → 3 N2 + 3 CO2 + 3 H2O +6 OH- (Step 2)

Overall,

6 NO3- + 5 CH3OH → 5 CO2 + 3 N2 + 7 H2O + 6 OH-

APPENDIX B: Consolidated analysis for month june-2024 at STP

RAW SEWAGE ANALYSIS

SL NO	PARAMETER	VALUES	LIMIT
1	Total flow (MLD)	1219.18	-
2	Average flow (MLD)	40.64	-
3	To old plant flow (MLD)	0.00	-
4	inlet bypass flow (MLD)	0.00	-
5	ISPS flow (MLD)	615.60	-
6	Average ISPS flow (MLD)	20.52	-
7	pH	7.16	6.5-7.5
8	BOD (mg/L)	298.67	<350
9	Total suspended solids (mg/L)	428.67	<450
10	COD (mg/L)	733.00	<800
11	Total phosphorus (mg/L)	7.05	<7
12	NH4-N (mg/L)	34.87	<45
13	TKN (mg/L)	48.53	<70

TREATED WATER ANALYSIS

SL NO	PARAMETER	VALUES	LIMIT
1	Treated Water (MLD)	1201.18	-
2	Average treated water	40.04	-
3	pH	7.26	6.5-9
4	BOD	5.03	<10
5	Total suspended solids	5.32	<20
6	COD	30.27	<50
7	DO	3.21	2-3.5
8	NH4-N	0.71	<5
9	Total phosphorus	0.70	<1
10	FRC	0.91	<1
11	Total nitrogen	5.00	<10

POWER AND CHEMICAL CONSUMPTION

SL NO	POWER CONSUMPTION	UNIT	VALUES	LIMIT
1	Total power consumption (BESCOM)	MWH	685.11	1158
2	Liquid	Kg	6005.88	-
3	Polyelectrolyte	Kg	760.00	-
4	Diesel	LTRS	1415.68	-

Written by:

Ruchitha Singh B

Amulya S

Ruthu M