What Different Sanitation Systems and Technologies Exist?

The choice of sanitation system and technology will determine the constraints of operation and maintenance, the rate of adoption by users, and ultimately the success of the intervention. Therefore, it is important to have a good overview of the most common available sanitation systems and technologies, and how differences between them affect future management decisions, from the very beginning. The types of system and technologies choice are directly linked and should be identified at the same time (see also Steps for Technology Selection).

Types of Sanitation Systems and System Templates 

The main factors that distinguish different sanitation systems are (Spuhler et al. 2022):

1. The type of user interface: this can be either a dry system (no flush but optional anal cleansing water) or a water-based user interface (cistern and pour-flush toilet).
2. The degree of centralisation: some systems treat or dispose of excreta and sludge on-site, while others transfer the sanitation products to decentralised or centralised treatment systems or to disposal/reuse technologies. Hybrid systems collect and treat or dispose of excreta and sludge on-site but the effluent is collected in e.g. a Simplified Sewer.
3. The type of transport: if the excreta or sludge is not disposed of on-site, the sanitation products are transported either through a sewer if these are in place and water for flushing is available, or, more commonly, through Manual or Motorised Emptying and Transport in trucks or barrels.

The most common systems primarily fall into one of the following four categories:

1. Dry on-site storage and treatment systems that do not require emptying such as Arborloos.
2. Dry on-site storage and treatment requiring emptying and safe disposal such as Urine Diversion Dry Toilets or Container-Based Toilets.
3. Water-based systems with sludge or pit humus production, such as Pit Latrines or Septic Tanks and Pour-Flush Toilets, that require emptying and faecal sludge transport (most often with trucks), treatment and safe disposal. These systems are also called Faecal Sludge Management (FSM) systems.
4. Water-based systems that connect to a sewered centralised collection and treatment.

Within the four categories above, there are many different possible sub-categories based on the technologies and how they are combined along the sanitation value chain. The full overview is presented in the following table, based on Tilley et al. 2014, WHO 2018 and Spuhler et al 2022.

A good overview on sanitation systems allows to make some preliminary selection. In a next step, technologies for each step of the sanitation value chain have to be selected. Using a clear framework to systematically match potential technology solutions with the relevant decision criteria makes technology selection easier. The Compendium of Sanitation Technologies in Emergencies or SaniChoice are tools that support technology identification and selection. See also What to consider when selecting sanitation technologies.

Types of Sanitation Technologies 

The main factors that distinguish different sanitation technologies are (Spuhler et al. 2022):

• Water requirements
• Onsite or offsite treatment
• Type of process: physical, chemical, biological
• Nature-based (e.g. constructed wetlands or composting) versus advanced, or high-tech technologies (e.g. Activated Sludge)

These factors will directly influence the technology requirements and factors that will influence the local appropriateness (see What to consider when selecting sanitation technologies).

Dry technologies (such as UDDTs or Container-based Toilets can be particularly useful in areas where water is scarce or where water-based sanitation systems are not feasible due to geographical or environmental constraints (lack of space, rocky soil, flooding). Moreover, dry on-site systems reduce the risk of greenhouse gas emissions.

Wet technologies such as Pour-Flush Toilets have the advantage to rapidly move away faeces from human contact. However, the dilution with water results in a relatively high volumes of hazardous waste that need to be stored on-site in Pit Latrines, Septic Tanks or Twin-Pits for Pour Flush. These wet technologies thus require high frequency emptying and transportation to avoid uncontrolled anaerobic digestion leading to greenhouse gas emissions.

Emptying and transport of sludge requires vehicles and good roads. Moreover, only if there is a disposal site and control of the correct disposal, the sludge will be safely treated and used. If vehicular emptying is not possible, manual emptying often takes place with sever risks to human health if not well controlled. Some alternative motorized technologies exist such as the vacutuc.

Nature-based solution such as Drying Beds or Constructed Wetlands generally require more space and more manpower for maintenance. However, they can be built independent from energy supply and require less skilled personal and mostly available spare parts. High-tech systems such as Activated Sludge Treatment can be very powerful and compact but generally rely on skilled man-power and large amounts of energy for pumping and aeration as well as chemicals and specialised spare part.

Resource Recovery

All sanitation systems can be upgraded for resource recovery, for example, introducing safe reuse of pit humus or dried sludge in agriculture, urine diversion and reuse as fertiliser for gardening, greywater irrigation or biogas production. Simple reuse options include the application of Compost or Stabilised Sludge as soil conditioner, the Use of Stored Urine as fertiliser, pellets made from Dried Faeces for cooking stoves or controlled Irrigation with greywater of trees or other crops (see also How to Ensure Safe Disposal and Reuse?).