How to Ensure Safe Disposal and Reuse of Treated Fecal Sludge and Other Sanitation Products?

Selecting the right processes and technologies for safe disposal or reuse is important to ensure the safety of the entire sanitation service chain, including in emergency relief. The aim is to minimise risks to people’s health and to protect the environment in the best way possible. Ensuring safe disposal or reuse requires the selection of Appropriate Technologies and clear Management and Operational Plans that follow local and international Standards. 

Relevance/Importance

The safe disposal or reuse of treated faecal sludge and other sanitation products is important for: 

• Public health: human excreta and other sanitation products, such as faecal sludge, contain pathogens (e.g. bacteria, viruses, worms and protozoa) that are hazardous to health. If not properly managed, these pathogens can be transmitted to humans through contaminated water, soil, or food, leading to public health risks 
• Environmental protection: faecal sludge, if not properly disposed of or reused, can pose a risk to the environment. Untreated faecal sludge can contaminate water sources, soil and air, leading to pollution and the degradation of ecosystems 
• Resource recovery: human excreta (urine and faeces) and all subsequent sanitation products (such as faecal sludge) contain nutrients (e.g. nitrogen, potassium and phosphorus), organic matter and energy that can be recovered and reused. These resources can be used e.g. as fertilisers in agriculture or as a source of renewable energy through biogas production 
• Social and economic benefits: the safe disposal and reuse of treated faecal sludge and other sanitation products can have social and economic benefits. Improved sanitation practices can improve the well-being of communities and enhance their quality of life. The productive use of treated faecal sludge in, for example, agriculture can also create jobs and income in the sanitation value chain 

Overview

Selecting Appropriate Technologies and their optimal System Configuration is necessary to ensure the highest possible efficiency of the entire sanitation system under the given framework conditions. The reuse and safe disposal of treated faecal sludge and other sanitation products is the last of the five functional groups of a sanitation system. It is just as important at this stage to protect people and the environment from risks in the best way possible. 

The technology and system selection for disposal and reuse depend on various factors. It is largely determined by the type and characteristic of the end product resulting from the previous step in the sanitation chain (e.g. dried faecal sludge) or the desired end product for reuse (e.g. biogas). Additionally, the selection of appropriate disposal and reuse technologies and their system configuration requires the consideration of factors such as geo-physical, socio-cultural, financial, institutional and regulative framework conditions as well as aspects related to skills and capacities.  

Different types of sanitation products require different treatment methods: 

• Surface disposal (see e.g. Surface Disposal and Sanitary Landfill) applies to solid end products such as stabilised sludge. It requires a significant amount of land and embodies an inherent hygiene risk if the product is not fully sanitised and contact with humans or animals cannot be avoided. The disposal site should be selected and designed to minimise the risk of groundwater contamination and other environmental impacts 
• Application of solids in agriculture (e.g. Application of Dried Sludge, Application of Pit Humus and Compost, ) makes use of the nutrients and organics contained in the dry material which can be either stabilised sludge or compost. It requires safe handling, demand for the products from agriculture and cultural acceptance. If the technology and human capacity are available, the sludge can also be further processed by, for example, composting or pyrolysis to improve the fertiliser properties of the sludge 
• Liquid products can either be Discharged into Surface Waters or infiltrated into the soil. Both can help recharge water resources (lakes, groundwater) but come with significant risks: only effluents that are pathogen-free and have low nutrient contents should be discharged into surface water. For soil infiltration (e.g. in Soak Pits or Leach Fields) it is important to know the soil filtration capacity and the groundwater table level. Liquids can also be used for Aquaculture or agricultural Irrigation but this again requires the control of pathogens and nutrient levels 
• Anaerobically digested sludge (e.g. in a Biogas Reactor) can result in some minor production of Biogas. The yield can be enhanced by adding organic solid waste or agricultural waste to the process. Biogas is then either burnt directly or used for cooking or heating 
• Urine could be collected separately and, after storage, be applied as liquid fertiliser in agriculture (see Application of Urine) 

Solids resulting from the treatment process must be stabilised before disposal or reuse. The stabilisation process may involve drying, composting, lime stabilisation or pasteurisation to reduce pathogens and must ensure that the biosolids meet local regulations for safe use. The quality of the solids must be tested regularly to meet the regulations for reuse and disposal. 

The Compendium of Sanitation Technologies in Emergencies, Section D (Use and/or Disposal) provides an overview of the different technologies and methods which can be used for treated faecal sludge and other sanitation products to ultimately return them to the environment, either as useful resources or reduced-risk materials. Topics like design, materials, applicability, operation and maintenance, health and safety as well as costs and social considerations are covered.  

The WHO Guide on Sanitation and Health (WHO 2018) describes key considerations of health risks associated with different technology solutions. Table 2.4 of Sanitation Quality Standards for Emergencies (FSM TWiG 2021) is a good and easily applied process for identifying the most suitable disposal route and corresponding Standards. The selected disposal route and standards should inform the treatment plant design (technology selection and sizing) and operation and management plans. Another useful orientation for control measures relating to the reuse of different sanitation products is provided in Sanitation Safety Planning, Annex 1-5 (WHO 2022). 

In emergency relief, humanitarian concerns are the priority, not sustainability and resilience, which is why disposal options are often more appropriate during an acute emergency phase than safe reuse options. However, reuse can contribute to the sustainability of the response by providing additional long-term benefits. The WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater Volume 2 (WHO 2006) and Volume 4 (WHO 2006) provide clear instructions about what to consider when reusing different products. The Guide to Sanitation Resource-Recovery Products and Technologies (McConville et al. 2021) provides information on all possible transformation technologies and reuse products.  

In addition to these guidelines, the Health and Safety of Operators and Workers must be protected through special education and Personal Protective Equipment.  

Process & Good Practice

• Design and operate the treatment plant according to the local disposal possibilities and specific end use/disposal objectives (as described in Table 2.4 of the Sanitation Quality Standards for Emergencies (FSM TWiG 2021)) 
• Use a risk assessment and risk management approach to identify, manage and monitor risk throughout the system (see Annex 1-5 “End Use or Disposal” of Sanitation Safety Planning (WHO 2022)). Ensure that, regardless of the source, both the liquid and solid fractions are treated before disposal or end use 
• Establish a process control and monitoring system based on the most suitable disposal route (see Table 2.4 of the Sanitation Quality Standards for Emergencies (FSM TWiG 2021) 
• Adopt a phased approach. The progression from the provision of emergency sanitation towards sustainable sanitation services should be seen as an ongoing process 
• Prioritise appropriately in each phase. During the acute emergency phase, the focus needs to be on:  
  • Public health 
  • Rapid scale-up: work towards servicing 100% of the population 
  • Pathogen reduction: monitor E coli in liquid effluent (<1000 CFU/100 ml) and helminth eggs in the solid effluent (< 1 n/g) 

• Ensure that after the acute emergency phase: 
  • Both treated liquid and solids should comply with national standards 
  • In cases where national standards cannot be met, a deviation is permissible with the agreement of the host government when reasons are carefully documented. In these cases, the disposal-based standards such as Table 2.4 of the Sanitation Quality Standards for Emergencies (FSM TWiG 2021) should be met 
  • The treatment plant should be designed and operated according to the most suitable disposal route and its corresponding standards. Table 2.4 of the Sanitation Quality Standards for Emergencies (FSM TWiG 2021) should be used to define the most suitable disposal route for both the liquid treated effluent and the solid treated effluent and to identify the relevant standards. Basic separation in a more or less liquid and more or less solid fraction is assumed, so the disposal routes for both fractions need to be defined