Is Fecal Sludge and Septage Management (FSSM) the answer to environmental sanitation? Yes, the sanitation service chain employed in FSSM ensures that the sludge collected from the households is treated. Post treatment, the end products can be reused or be safely disposed into the environment.
The aim of FSSM is:
- To break the fecal-oral transmission of pathogens and protect environmental health
- To reduce the pollution load for the surface water bodies by restricting indiscriminate disposal
FSSM caters to the sludge in the onsite containment units such as a septic tank; which may pose questions regarding holistic nature of the approach towards solving environmental sanitation crisis.
But FSSM is not a comprehensive solution.
The septic tank effluent and the grey water flowing into the road side drains leading to surface water bodies are also the major cause of environmental pollution. However, by implementing FSSM, it is ensured that the treatment performance of the onsite containment unit is maintained, providing primary treatment to the blackwater and decreasing the environmental pollution to an extent.
In case of tier I and tier II cities, the impact of FSSM is significant because the sheer quantum of the sludge which is collected is large. This means that the septic tanks which are desludged at the time interval of 3-5 years are being maintained; thus, reducing the pollution load discharged into the environment. In the absence of Faecal sludge and Septage Treatment Plant (FSTP), indiscriminate disposal of sludge adds to significant pollution load. The Urban Local Bodies (ULBs) of tier I cities generally have a better management system and resources. This enables them to develop and implement byelaws thereby providing an opportunity to sustain a good tax collection efficiency. These management aspects play a crucial role in the operation and maintenance (O&M) of the FSTPs thereby ensuring sustainability of investments made through grants or funds.
Apart from tier I cities, the smaller ULBs also known as semi urban centers are characterized by low population densities, face diverse challenges. These ULBs are not only struggling with inadequate human resource capacity, but also lack management system for maintaining its assets thereby leading to lower tax collection efficiency. In such cases, the FSTPs are more of a burden to the ULBs rather than assets. Scientific land disposal mechanism such as entrenchment (deep row entrenchment) is a perfect fit in such cases. Entrenchment with minimal capital investment (which can be self-funded by ULBs without relying on grants or funds) and very low O&M cost is more affordable and sustainable solution for smaller ULBs.
In semi urban centers, it is more important to focus on wastewater (septic tank effluent and grey water) flowing through network of pucca and kaccha nallas into the surface water bodies. For this, intercepting drains and providing secondary treatment using natural treatment systems and not treatment plants are recommended. These treatment systems do require a large area and capital investment which can be constraints. However, the area and capital investment required is comparable to that required for FSTP. In absence of tertiary treatment, the treatment systems will not be able to meet the stringent norms recommended by the Central Pollution Control Board. In spite that, this will still lead to higher reduction of pollution load as compared to functioning FSTP meeting the stringent discharge standards.
In fact, for Semi urban cities, each rupee invested for treatment of liquid waste potentially provides more sustainable environmental returns as compared to investment in setting up one FSTP.
Due to the lack of appropriate case study and literature, this premise is theoretically proven for a ULB practicing scheduled desludging at an interval of 3 years with a daily collection of septage up to 10 KLD. It is to be noted that such a ULB will also produce wastewater close to 1 MLD which also needs to be managed. Although, the concentration of septage [mg of COD per liter] is typically thirty times higher than that of wastewater, the pollution load [kg of COD per day] of 1 ML wastewater will be still over two times higher than that of 10 KL septage.
If the parameters of area and capital investment for wastewater treatment system (1 MLD) and FSTP (10 KLD) are kept same, the decentralized-non mechanized wastewater treatment system will be able to provide secondary treatment. Assuming an average treatment efficiency, the wastewater treatment system will be able to remove half of the COD load from the wastewater, making it more beneficial as compared to having an FSTP.
Not to forget that quantum of treated end products in the case of wastewater treatment system will be much larger as compared to the an FSTP. Thus, if managed well can feed the urban lakes and ponds or if managed by a Public Private Partnership approach, then a good revenue stream is available to ULB along with managing the liquid waste at the city scale.
In case of demand desludging, where the daily collection of the sludge is variable and the desludging time interval is more than 5 years, the management of septic tank effluent and grey water should become the priority. Scientific surface disposal in the form of entrenchment combined with natural wastewater treatment system will conform to all aspects of sustainability and be more beneficial for the ULB as compared to only setting up an FSTP. The entrenchment of septage will reduce the fecal oral transmission of the pathogens as pathogens cannot travel more than few meters in soil strata and wastewater treatment system will reduce the pollution load to surface water bodies. The end product, that is the bio solids can be recovered the entrenchment system and applied in agriculture after following Guidelines for safe reuse of wastewater and excreta recommended by the World Health Organization.
Lastly, looking at the race of installing FSTPs in various states, it is necessary to understand that FSTPs might not be the appropriate and the only indicator to measure the success of FSSM in absolute sense. Simple and safe disposal techniques (and not technologies) are also equally effective in semi urban cities for completing the sanitation service chain of FSSM.
Author: Dhawal Patil