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Technology Review of Urine-diverting dry toilets (UDDTs)

Summary

This technology review deals with a type of toilet designed specifically for dry excreta management called the urine- diverting dry toilet (UDDT). It is a sanitation system for households and public facilities as well. The functional design elements of the UDDT are: source separation of urine and faeces; waterless operation; and ventilated vaults or containers for faeces storage and treatment. UDDTs may be constructed with two adjacent dehydration vaults or one single vault with interchangeable containers. This publication offers a complete overview of UDDT functions, design considerations, common operation and maintenance issues and generalised installation costs. Its focus is on applications in developing countries and countries in transition, although UDDTs are also applicable in developed countries.

 

The UDDT technology was originally promoted in connection with safe reuse of excreta. However,the primary focus of UDDT implementation has gradually shifted from that of excreta reuse to the broader objective of creating an odourless, dry and versatile toilet that is applicable across wide range of geographic and economic contexts. Many successful examples of largescale UDDT programmes, such as those found in Lima, Peru and eThekwini (Durban), South Africa, dispose of treated excreta instead of reusing it, as it is considered more practical, convenient or acceptable to the users.

 

The primary advantage of UDDTs, as compared to conventional dry latrines like ventilated improved pits (VIP) latrines, is the conversion of faeces into a dry and odourless material. This leads to an odour and insect free toilet which is appreciated by users and to the simple removal and less offensive and safer handling of the faecal material once the toilet has filled up. Moreover the risk of water pollution is minimised through the safe containment of faces in aboveground vaults which also allows the toilets to be constructed in locations where pit-based systems are not appropriate. The faeces are however not entirely sanitized when removed from the toilet, so precautious handling is obligatory. In scenarios with reuse of excreta in agriculture, a post-treatment of faecal matter and storage of urine is advisable to ensure adequate sanitization.

This publication provides comprehensive design guidelines for all functional UDDT components, including urine diversion (UD) pedestals, benches and squatting pans, dehydration vaults, single vaults with interchangeable containers, and urine piping and storage systems. Possible design modifications are discussed to ensure the toilet’s suitability for small children, the elderly and persons with disabilities. Additionally, all relevant aspects of excreta management are described including treatment, disposal, reuse and maintaining hygienic quality standards.

Emphasis is placed on recent technical innovations that allow the UDDT to be integrated in a wider range of applications. The bench design, a sitting type of UD interface that minimizes the need for stairs leading up to the toilet, is presented as a possible solution for indoor installations and means of providing barrier-free access. Other designs are presented for a variety of contexts, including indoor and outdoor installations, schools and public toilet blocks, flood prone areas and floating villages.

This technology review also describes common O&M problems, such as blockages in urine piping systems, wet conditions in the dehydration vaults and faulty construction. Possible fixes and preventative maintenance routines are emphasized as a means of ensuring the toilet’s sustainability. This publication challenges the common perception that UDDT installation costs are prohibitive for the poorest members of society. A number of low-cost UDDT designs are available that take advantage of locally available construction materials and can help tailor the toilet technology to available budgets.

According to the Joint Monitoring Program (JMP), approximately 2.5 billion people lack access to improved sanitation facilities, with 1.1 billion still practicing open defecation (UNICEF and WHO, 2012). Knowledge and practice of critical hygiene behaviors, such as hand washing after toilet use, are also widely lacking. Consequently, the ingestion of faecal pathogens from contaminated food and water resources as well as faecal- oral transmission are a leading cause of disease and preventable death, especially in children under five years.The effects of inadequate sanitation, hygiene and resulting diarrheal disease are dramatic: in 2010, the

World Health Organization (WHO) reported that worldwide the impact of diarrheal disease on children is greater than the impacts of HIV/AIDS, tuberculosis and malaria, combined. Due to their relative affordability and simple and waterless operation, pit latrines are common in developing and transitional countries. However, pit latrines can spread faecal contamination to water resources, especially in associated with faecal sludge removal or excavation of new pits when emptying is not feasible.

Increasingly, limited water supplies and the high cost of construction of wastewater infrastructure make sewer- based sanitation impractical in many regions. Water-based systems dilute excreta and create large waste water streams that necessitate the construction of technologically complex and expensive treatment facilities. It is estimated that 90% of all wastewater in developing countries is discharged untreated directly into water bodies (Corcoran et al., 2010), a clear indication that sewer-based sanitation is not a viable solution for many parts of the world. Moreover, pharmaceutical residues in treated wastewater could have negative impacts on human health, and lead to the evolution of resistant strains of microbes. Expectations and attitudes surrounding sanitation are widely variable and influenced by both societal norms and personal preference. While improved hygienic standards, reduced contaminant impact and minimization of water usage may be the goal of sanitation practitioners, toilet users generally strive to improve their current sanitation situation with regards to odour, insect infestations, privacy, comfort and ‘prestige’.

The UDDT is a dry excreta management system that, since the late-1990s, is seen as a viable alternative to pit latrines and flush toilets in developing countries and developed countries respectively. However, significant barriers to more universal acceptance of this technology remain. To date, a general lack of awareness, a limited supply of prefabricated UDDT components and a low interest in financing sanitation services, have all acted as impediments to the construction of UDDTs.

Historical development

The earliest documented dry toilets with urine separation were installed in multi-storey houses in Yemeni towns and were, until recently, used continuously for hundreds of years. The UDDTs with double dehydration vaults that we know today were originally designed around 1950 in the Kanagawa Prefectural Public Health Laboratory in Japan and further developed in Vietnam in the 1960s as a means of increasing the hygienic safety of excreta reused in agriculture.1

Since the 1990s, modifications of this design have been promoted in countries like Mexico, Guatemala, El Salvador, India and Sweden. Ventilation pipes in the faeces vault were gradually integrated and allowed for the installation of UDDTs inside houses. More recently, prefabricated ceramic or plastic UD squatting pans and pedestals have become available on the market, generally increasing the durability and perceived prestige associated with the system. The design was further adapted in India and West Africa to accommodate anal cleansing with water, by including a separate anal cleansing pan with a drain to divert wash water into a dedicated disposal or treatment system.

As early as 2000, the bench UDDT, which is a design that allows the user to sit directly on the vault, began to be promoted in Ecuador and Peru. This model is easily incorporated into existing housing structures and has emerged as a popular design for indoor installations (see Section 10.2). UDDTs have also been commercially produced in Sweden since the mid- 1990s. These commercial products are often installed in locations where piped sewerage is not available, such as remote summer cottages.

In 2001, the EcoSanRes Programme was initiated at the Stockholm Environment Institute (SEI). This was followed shortly thereafter by the establishment of the ecosan program at GIZ. Together these two government-funded programmes have helped to disseminate knowledge of UDDTs and have triggered the promotion of this technology in developing countries and countries in transition. The exact number of UDDT users is impossible to determine, but a rough estimate based on known projects in 84 countries puts the number at approximately 2 million worldwide.

     

 

 

 

 

 

 

 

 

                           


            

Current Issue: Africa Water & Sanitation & Hygiene March-April 2017 Vol.12 No.2