Themes

Infrastructural Innovations

While conventional sewerage is usually an effective system for sewage collection and transportation and treatment, for various reasons, widespread adoption in all sizes of urban areas in India has not been possible. Under the principles of City-wide Inclusive SanitationCWIS focuses on providing urban areas with access to and benefits from adequate and sustainable sanitation services, including the safe, effective, and sustainable management of all human waste along the whole sanitation service chain, there is growing recognition that improving and expanding non-sewered sanitation approaches will be a crucial aspect of current and future urban development and sanitation planning—because it is already what many people around the world use, and it has the potential to be cost and resource effective for many cities and communities. In many cases, septage management may also be comparatively economical than conventional sewerage systems, in terms of capital cost and O&M cost.

The National FSSM policy, announced by the GOI in February 2017 for widespread implementation of FSSM in all ULBs, has also placed emphasis on the necessity of implementing septage management plans with appropriate faecal sludge and septage treatment facilities. However, multiple difficulties are faced throughout the sanitation service chain while adopting FSSM for non-sewered connections in the cities. These challenges can be broadly covered under collection and containment, conveyance systems, and treatment aspects of non-sewered connections.

(Figure-1: Challenges faced across the non-sewered connections. Source: Ministry of Housing and Urban Affairs Government of India)

  • Lack of awareness/ willingness, availability of space and finances to build the supply, compromise in quality, and dilapidated or insanitary toilets
  • Inaccessible septic tanks, absence of septic tank covers also hinder collection systems
  • In many cases, due to lack of space, the superstructure is built right above the septic tank rendering it difficult to desludge without breaking the slab
  • Single pit toilets, insanitary toilets, unlined septic tanks, outlet of septic tank directly to drains are also challenges in the collection system which pose a high risk to environment.

  • Very low desludging frequency against the recommended cycle, unsafe handling of septage by desludging operators and lack of monitoring mechanism for informal sector
  • Lack of awareness about environmental hazards leads to desludging of septic tanks on when they are full
  • Due to such infrequent cleaning of septic tanks, overflow of effluent mixed with sludge is often witnessed in drains
  • The septage in the septic tank also solidifies over time making it difficult to desludge

  • Due to lack of treatment facilities for septage, it is disposed in hazardous manner in open in the city
  • After desludging, septage is generally disposed at the solid waste dumping site of the city, or in open land or water bodies in the city outskirts

While efforts have been made to address the access component of the sanitation service chain, the current situation of the rest of the value chain in most cities is considered poor, according to an NIUA report: most septic tanks do not have access covers and are larger than the standard sizes so that the desludging period is increased. Only 2-4% of total septic tanks are cleaned annually and due to less demand, the cities have poor infrastructure to cater to the same. There is little to no treatment provision for septage and it is disposed of haphazardly without treatment into the environment. Thus, there is a need to address the entire sanitation service chain in Indian cities. This includes ensuring access to toilets, enforcing regulations for appropriate collection systems, moving towards periodic cleaning of septic tanks as per norms and treatment and reuse of collected septage.

FAECAL SLUDGE AND SEPTAGE MANAGEMENT TECHNOLOGY AND FINANCING MODULE - Part A (NIUA)

It would be crucial for city, state, and local governments to make corrections to the issues in the household-level on-site systems to maximize the benefits from sanitation investments as non-networked sanitation can be positioned in mainstream planning and governance systems for citywide sanitation. The management of on-site sanitation cannot be accomplished by a septic tank alone. The standard "septic tank system" is a full-service remedy and consists of a tank and a subsoil dispersion system. However, the household must voluntarily participate in the installation of soak pits next to current septic tanks and the upgrading of septic tanks to newer, more advanced on-site systems.

Conveyance and treatment systems need ongoing financing for construction and maintenance. Subsoil dispersion methods are not appropriate for urban settings, despite their conventionality. Their spatial density also serves as a crucial and restricting component. Most Indian cities have neighbourhood-level density is high, making the promotion of subsoil dispersion systems an undesirable alternative. Technologies for desludging and conveyance trucks should be purchased based on assessment of local conditions in the city. Parameters for assessment of desludging trucks include distance of treatment site, road width, characteristics of septage, fuel requirement, size of septic tanks/pits, and the financial budget of emptying services. Based on this, choice between conventional vacuum tankers, mini tankers/ vacutugs, and mechanized gulpers can be made.

For selecting an appropriate conveyance system, an assessment of water availability, ground condition, ground water level and contamination is required. Human-powered or motorized emptying and transport options can be explored, and subsequently, the sludge and septage emptied from OSS must be transferred via transfer stations (permanent/mobile) or holding tanks.

For treatment, it is important to realise that for the conversion of faecal sludge (FS) into a product that is safe for end use or disposal, several processes need to take place. FS typically contains large volumes of water and hence needs to be dewatered, which can be achieved on its own, or in combination with solid / liquid separation. Depending on the end goal, further treatment needs could include converting organic matter into a stabilised form and/or pathogen reduction.

(Figure 2: Infrastructure Technology Options for Value Chain)

General selection criteria for an appropriate FSS Treatment Technology takes into consideration:

  • Local context – characteristics of sludge, quantity of sludge discharged, climate, land availability, cost, and interest in end-use
  • O&M requirement – skills needed for O&M and monitoring, availability of spares, repair capacity (see Principle 4)
  • Costs – Investment costs, O&M costs, affordability for payer (end-users, households, ULB)
  • Technical Performance – effluent and sludge quality, and conformance to regulations and standards.
(Figure 3: General selection criteria for an appropriate FSS Treatment Technology)
Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries: a Practical Guide
Decentralized Wastewater and Fecal Sludge Management: Case Studies from India ADBI

There is a great need for the development of appropriate inclusive Sanitation technologies, even though solutions for entire inclusive Sanitation systems will not rely on technology alone and must be considered within the local context. New technologies are in general based on pioneering developments in research, and historically research agendas have been driven by countries where centralised sewer-based sanitation solutions are the accepted norm. This points to a need for solution-oriented inclusive Sanitation research to be conducted in countries where it is directly relevant. In addition, for new knowledge to get taken up and influence policy, it requires local researchers working together with the urban governments that are responsible for inclusive Sanitation. Due to the urgent need for technical solutions, research and implementations need to continue to be conducted in parallel, getting to scale as rapidly as possible. Technologies need to be selected not only based on the specific characteristics of FS, but also on factors such as the local market demand for resource recovery of treatment products. Provided here are some examples of current research.

COLLECTION AND TRANSPORT

Currently, the best available technology for sludge removal is vacuum trucks, but they are typically expensive and cannot reach households located on narrow streets and alleys. The BMGF-funded Omni-ingestor project aims to develop equipment that is more dexterous, evacuates FS more quickly, can remove dense FS efficiently (> 40% solids) and is also able to dewater FS onsite. As water is heavy and therefore expensive to transport; dewatering FS and treating the effluent onsite would allow for the treated water to be directly reclaimed or safely disposed of in drains. This would greatly reduce transport costs and allow for more emptying operations performed between trips to the FSTP, as well as reducing time spent in traffic. Various prototypes are currently being developed by the private sector.

ONSITE TREATMENT TECHNOLOGIES

Achieving reliable levels of treatment with onsite sanitation technologies presents a very challenging problem due to factors such as the lack of technical management, demands for reliable energy and high costs. Some examples of technologies include hydrothermal carbonisation, microwave technology, supercritical oxidation, pyrolysis, and electrochemical processes.

The sludge from pit latrines or septic tanks is typically dumped untreated into open sewers, irrigation fields, open lands, or surface waterways as they get full. Several (FSTPs) have been established in various parts of the country to address the difficulties in preserving public health and the environment. However, there are some specific issues at every FSTP observed with FSTPs

Case study: Scheduled Desludging Activites

Irregular receival of FS: Some FSTPs receive FS more frequently than the plant's treatment capacity and occasionally less frequently than the plant's treatment capacity. These irregularities may result in performance issues. Scheduled desludging activity could provide a solution to this issue by providing a continuous FS supply for treatment.

Case study: Requirement for Sufficient Spacing

Space constraint: Sufficient spacing is required for optimisation of co-composting process specifically mixing ratio of dry FS and MSW/vegetable waste. Clustered approach with FSTPs that are closer to each other, or a private provider willing to coordinate with nearby cities could address this issue.

Case study: Public Private Partnerships (PPP)

Low availability of vacuum trucks: In few cases, only one vacuum truck for the delivery of FS is available leading to over-burdening of the truck/owner for FS delivery. Through public private partnership (PPP), private providers can carry out desludging activity with their own trucks. This would performance-based contract and would reduce the capex burden on local government and improve the service.

Case study: Supplementary Heating Sources 

Insufficient solar energy to run FSTPs: Some FSTPs uses solar energy to operate, increasing the system's energy efficiency. However, the energy produced from solar radiation is insufficient to fulfil the FSTP's energy needs. As an energy reserve, supplementary heating sources including fuel, grid electricity or electricity from renewable sources, and heat pumps could be used. Energy storage devices are used to store solar thermal energy during periods of high sunlight and use it during periods of low or no sunlight.

Case study: Assessment of Treatment Units

Industrial effluents: In some FSTPs, industrial effluent is received occasionally instead of FS from the vacuum trucks, and it becomes difficult for the current treatment system to remove the pollutants, particularly heavy metals. To distinguish between residential and industrial sludge, and to assess the performance of the treatment units, tests such as color, odor, temperature, pH, and electrical conductivity are needed to be carried out on a weekly basis.

Academic institutions and philanthropies are developing ground-breaking technologies that improve efficiency, cost-effectiveness, and quality of sanitation infrastructure. Some examples:

  • The Research Triangle Institute is developing an integrated toilet technology that will separate solid and liquid waste, dry and burn solid waste using a combination of mechanical, solar, and thermal energy (primarily driven by down-draft gasification), disinfect liquid waste, and convert the resulting combustion energy into stored electricity.
  • Caltech is developing a comprehensive, human waste treatment and toilet system that has at its core a photovoltaic-powered (PV), self-standing electrochemical chemical reactor that generates hydrogen for energy and nitrogen for fertiliser as by-products of treatment.
  • Loughborough University is developing a system that is comprised of a draining balance tank; filters; high temperature pressure reactor; and evaporator-sodium chloride separation. The system operates in three stages: solids-liquid separation, followed by auto-thermal treatment of the solids to provide heat for water and salt separation.
Faecal Sludge Management: Systems Approach for Implementation and Operation (Chapter 5: Overview of Treatment Technologies, Chapter 18: Way Forward)
Compendium of Sanitation Systems and Technologies (2e), Swiss Federal Institute of Aquatic Science and Technology (Eawag)

Sanitation is a multi-step process in which human excreta and wastewater are managed from the point of generation to the point of use or ultimate disposal. A Sanitation System is a context-specific series of technologies and services for the management of these wastes (or resources), i.e., for their collection, containment, transport, transformation, utilization or disposal. A sanitation system is comprised of Products (wastes) that travel through technologies that can be selected according to the context. By selecting a Technology for each Product one can design a logical Sanitation System. A sanitation system also includes the management, operation and maintenance (O&M) required to ensure that the system functions safely and sustainably.

By ordering and structuring tried and tested technologies into one concise document, the following matrix is a useful planning tool to help sanitation professionals make more informed decisions.

SEE ATTACHED EXCEL SHEET WITH MATRIX

Cost Analysis of Faecal Sludge Treatment Plants in India: Life Cycle Costing & Contracting Models of FSTPs

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