Rural Water and Sanitation

Excreta as resource: Looking at recovery, reuse of faecal sludge in UP

A critical link in faecal sludge and septage management value chain is reuse of by-products generated, which include treated water as well as biosolids

 
By Ekta Gupta, Praveen Chature, Rahul Mankotia
Last Updated: Thursday 28 May 2020

 

More than half the urban population in India does not have an access to sewerage network and is dependent on onsite sanitation systems (OSS). The faecal sludge from OSS needs to be regularly emptied and safely disposed of so that it does not contaminate the environment.

This issue has been largely ignored in India, but with the National Faecal Sludge and Septage Management Policy in 2017, it has gained traction. Now, a number of faecal sludge treatment plants (FSTP) are being implemented across the country.

The situation is no different in Uttar Pradesh, the most populated state in the country. A state septage management policy was issued in 2019 and the state decided to implement FSTPs. Two FSTPs are already operational in Jhansi and Unnao.

However, a critical link in faecal sludge and septage management (FSSM) value chain is reuse of the by-products generated from FSTPs, which include treated water as well as biosolids.

The reuse of biosolids or manure in particular, has huge potential in agrarian states like Uttar Pradesh. One such project in pipeline, where the reuse component has been emphasised upon, is in Chunar. Delhi-based non-profit Centre for Science and Environment (CSE) is the knowledge partner.

The calculation (in table below) shows the revenue generation potential of this by-product which can help in sustainability of the project.

FSTP capacity (in Kilo litre a day) 10
Number of planted drying beds 6
Size of planted drying bed (in square metre) 56
Total FSS loaded on 6 beds (in kilogram) 60,480
Since dry FSS / compost contains 25% moisture, total weight would be (in kg) 80,640
Assume 10% loss during filtration and handling, net compost available (in kg) 72,576 kg (72.6 tonnes)
At conservative side, selling price at the site is assumed Rs 3,000 / tonne (Rs 3 / Kg)
Amount recovered by selling of total compost Rs 217,800 / year

Revenue generation potential of the FS by-product. Source: CSE, India

There are around 60 FSTPs of 32 kilo litres per day (KLD) being implemented in major cities in Uttar Pradesh through Atal Mission for Rejuvenation and Urban Transformation funding. From these cities alone, there is a potential of 13,200 tons / annum of compost generation per annum, with potential to generate Rs 4 crore / annum revenue per annum.

Manure is not the only resource which can be recovered from excreta. The faecal sludge also contains organic carbon that can be used to generate energy in the form of heat or electricity — the calorific value of faecal sludge is as high as many other commonly used organic fuels.

They following case-studies suggest possible models to mainstream resource recovery and reuse component in the FSSM value chain.

FSTP in Sakhipur, Bangladesh

CSE had organised a study visit for officials from Uttar Pradesh to this facility. This FSTP is unique, since the dried faecal sludge from FSTP and organic municipal solid waste are co-composted to ensure improved final compost.

The project addresses the twin problems of solid waste and faecal sludge management. Currently, the plant handles 1,200 tons of faecal sludge and 125 tons of solid waste annually. It produces approximately 24 metric tons of compost every year.

The municipal authority has dedicated farmer schools that educate and sensitise local farmers on various best practices. Through such initiatives, the ULB has been able to sell compost directly to local farmers for $0.20 / kg, and have been able to generate high demand by farmers for the compost. Source segregation and sourcing organic waste is a challenge for this project. 

Waste to Energy plant using biomethanisation in Nashik

During CSE’s visit to Nashik while conducting surveys for Shit Flow Diagram, the team came across a pilot project with potential to be a model for resource recovery from faecal sludge.

The Waste-to-Energy plant in Nashik uses biomethanation potential method using biogas digester to co-digest food waste (FW) collected from hotels and septage from public toilets in 2:1 ratio.

  • Advantages: This process generates two revenue by-products — biogas that is used for electricity generation / cooking and slurry, which is treated using sludge drying beds. This treated sludge is used in SWM plant for co-composting with organic solid waste to produce the organic fertiliser. The fertiliser is sold to local farmers.
  • Limitations: The problem with this facility is segregation. According to GIZ’s guidelines, only cooked FW can be used in the plant, but mixed wet waste is delivered instead.
  • There is a lack of FW supply to generate electricity due to contract (limited to hotels). These limitations demand additional manpower / resources in order to run the plant efficiently.

Based on the table below, if the plant is running in full capacity of 30 tons / day, it should generate 2,600 cubic metre of biogas, power generated would be 4,800 kilo watts and sludge generated would be 3 ton / day.

In an optimistic scenario, revenue generation would be Rs 25 lakh a month. But this is not the case in the current scenario. Due to contract with the NMC, source for FW is limited to the hotels in the city hence, insufficient to run the plant at full capacity.

At present, 20 ton / day FW is required but only 5 tons / day FW is received. However, if the entire city’s FW is supplied, then this is the best source for revenue generation and resource recovery.

Sanitation remains foremost a ‘social model’ and is seldom considered a business. Resource recovery and reuse approach helps in shifting the focus from waste being regarded as something to be disposed to waste being regarded as a valuable resource and move towards a more circular economy.

Source of collected Faecal Sludge (FS) Public Toilets
Technology/ Process used to destroy pathogens from septage Hygenisation ( Proposed )
Plant capacity (t / d)  30 t / d
Quantity of FS collected (KLD)  10 KL / d
Number of vehicles used to collect FS  1
Number of vehicles used to collect food waste every day  2
The ratio of food waste (FW) to FS used for the co-processing (FW: FS)  2:1
Quantity of biogas generated (m3 / d)  2,600 m3 (Approx.)
Power generated in the plant (units / day)  4,800 KW
Power supplied to MSEB (units / day)  3,300 KW
Quantity of Sludge generated (t /d) ( dry compost )  3 t / d
Quantity of matter disposed at the landfill (t / d)  0 ( Zero Discharge)
Quantity of leachate generated (KLD) ( Digester Overflow liquid )  23 KLD
O & M cost of the plant (Rs / month)  Rs 5 lakh per month 
Revenue generated (Rs / month) ( power + C&T + P&D + Compost )  Rs 25 lakh per month

 Source: Interview with the waste to energy plant operator

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