General discussion, conclusion and recommendations
Addressing the global sanitation crisis requires effective and sustainable interventions for faecal sludge management. Worldwide, 2.7 billion people are using onsite sanitation systems, with a number expected to increase to 5 billion by 2030 (Strande et ah, 2014) due to rapid population growth and increasing emergence of LIHDS in cities of developing countries. Zooming in on Kenya, more than 100 LIHDS in Nairobi have emerged owing to a lag in planning and development of infrastructure to meet the demands of the growing population (AWF, 2013). These settlements, as reported in other countries, are characterised by poor sanitation, haphazard development, high population, high poverty levels and insecure land tenure (Katukiza et ah, 2010; Kulabako et ah, 2010; Mels et ah, 2009; Scott et ah, 2013).
Consequences of poor sanitation are dire; owing to the high pathogenic load in excreta, it poses high environmental and public health risks (Winblad & Simpson-Hebert, 2004), (Feachem et ah, 1983). Engineers and city planners previously focused on conventional sewer- based sanitation systems, which, in addition to being expensive to develop (Lalander et ah, 2013; Mara, 2013), require significant costs in maintaining and upgrading the infrastructure (Kone, 2010; Schertenleib, 2005; Zimmer & Hofwegen, 2006). Onsite sanitation systems, previously viewed as a sanitation option solely viable for rural areas, were adopted as a sanitation solution for the urban LIHDS (Strande et ah, 2014). However, thus far, there are no, or very limited, proper management systems available for the faecal sludge (FS) generated by the onsite systems, compromising public health (Mbem et ah, 2016). Recent technological advances in sanitation options has resulted in different onsite sanitation technologies, e.g. urine diverting diy toilets (UDDTs), pee poo bags, pour flush toilets connected to septic tanks, etc. (Katukiza et ah, 2010). However, thus far, these technologies have not been adopted for widespread usage with about 98% of the sanitary facilities remaining being pit latrines (See Chapter 2, Figure 2.3); consequently, sanitation conditions remain dire (Gulis et ah, 2004; Mberaet ah, 2016; Zulu et ah, 2011). Chapter 2 describes the impediments to LIHDS sanitation enhancement in Kibera, Kenya.
hi Kenya, there is no policy framework governing planning, implementation and management of onsite sanitation within the settlements (Mansour et ah, 2017). In addition, institutional set-up and regulatory functions of urban sanitation sector are shared by different institutions leading to un-coordinated/imregulated activities among the stakeholders involved along the sanitation chain. For example, whereas sewerage sendees fall under the authority of the Ministry of Water, onsite sanitation is under the Ministry of Health (See Chapter 2). Moreover, NCWSC is mandated to provide FS disposal points, NCC is mandated to issue business permits for sanitation business and enforce public health rule while NEMA regulates discharge into the sewerage system.
Sanitation improvement efforts among LIHDS, mainly focus on provision of sanitation facilities (human interface), neglecting sludge management and disposal (See Chapter 2, Section 3.1.1). Zooming in on Kenya, Nairobi City Water and Sewerage Company is mandated to provide FS disposal points, either to sewage treatment plants or at designated manholes along
the sewer line. This has not been actualised, aggravating FS management, with the demand for service outstripping the available supply. Owing to overcrowding, lack of vehicular access, and lack of potential for investment in the sector, 79% (see chapter 2, Figure 2.5a) of pit emptying sendees are provided by illegal pit emptiers and 18% by registered manual pit emptiers. Moreover, due to lack of FS disposal points, 85% (See Chapter 2, Figure 2.6) of all sludge is disposed to the environment untreated either directly to river bodies or storm water drain, causing health problems in the communities (Gulis et al, 2004; Mberu et al, 2016; Zulu et al, 2011). Moreover, health and safety concerns were not a priority among the pit emptiers (See Chapter 2, Figure 2.7). Lack of disposal sites and protective gear for, pit emptiers are oblivious of the health risk it poses to the community. Training on safe emptying practices is critical to reverse this trend.
Operation and maintenance of sanitation facilities play a distinct role in their overall sustainability (See Chapter 2, Section3.1.4). Pay and use approach of sanitation provision enhances operation and maintenance initiatives. Whereas in 73% of the free to use community facilities were abandoned on fill up, 89% and 77% (See Chapter 2, Figure 2.4) of community- based organisation (CBOs) and entrepreneur managed facilities, respectively, were well managed, hi CBO and entrepreneur managed facilities, a fee is charged per use of the facility, which ranges between ($ 0.03-0.1) per every use. The fee that is charged is used to facilitate management operations within the facility i.e. cleaning and emptying.
Adoption of pit latrines in Kibera remains high 98% (See Chapter 2, Figure 2.3), despite recent advances in technological development on other onsite sanitation technologies, such as, UDDTs, pee poo bags, pour flush toilets connected to septic tanks etc. (Katukiza et al, 2010). Apparently, these novel technologies remain non-recognised during sanitation planning. Thus far, the sanitation provision approach is supply driven where cost and space are key considerations in identifying the most suitable technology, neglecting accessibility, social- cultural issues and soil conditions (See Chapter 2, Figure 2.2).
Partnership-based sanitation provision improvements provide an entry point for broader initiatives to improve living conditions in informal settlements. With regard to the LIHDS located in or near Nairobi, the Umande Trust business model provides such partnership-based sanitation provision. Umande Trust is a non-governmental organisation (NGO) and is registered by National Environmental Management Authority (NEMA) and Nairobi City Council (NCC). Their business model combines basic sendee provision with economic empowerment of the communities (http://umande.org/). They enlist sendees of CBOs in management of bio-centres, who thereafter contract registered pit emptiers to offer emptying sendees. In Accra, Ghana, a partnership between government and private sector enhanced faecal sludge management (Boot & Scott, 2008). A similar case was reported in Bamako, Mali (Marc et al, 2004).
The need for implementing an effective treatment technology for FS collected from LIHDS can’t be underrated. While conducting our a survey carried out in this study (Chapter 2, Section 3.1.4), 88% of facilities visited were operational signifying that emptying sendees were functional. However, 85% of the collected FS ends untreated in the environment via unhygienic disposal pathways (See Chapter 2, Figure 2.6(b)). Moreover, enterprises that have adopted other sanitation options, such as UDDT, also require treatment options for the collected FS. Treatment of UDDT-FS is emphasised in literature, since addition of ash and sawdust after toilet use is insufficient for pathogen inactivation (Niwagaba et al, 2009a). A case in point is Sanergy- Kenya, a social enterprise working on sanitation enhancement within LIHDS in Kenya. In the business model of Sanergy, FS is collected in specially designed sealable, removable containers (sometimes called cartridges). Serving about 100,000 LIHDS residents per day, it collects and transports approximately 6 Kilo tonnes of UDDT-FS annually (http://www.sanergy.com,'). By ensuring that the collected FS is well treated before disposal/ reuse, the health risk associated with open dumping of FS would be reduced (See Chapter 3, Section 3.3).
Owing to lack of space, decentralised treatment units are a viable option for management of FS from LIHDS. In particular, anaerobic digestion (AD) provides an attractive approach in FS treatment (Rajagopal et al, 2013) as it can be implemented at any scale, either onsite or offsite. In addition to FS stabilisation, AD offers biochemical energy recovery through methane production from the biodegradable organic matter in the FS. Moreover, the resulting liquid flows from AD plants are characterised by high concentration of nutrients giving an effluent with good fertilising properties (Avery et al, 2014; Fonoll et al, 2015; Nallathambi Gunaseelan, 1997; Romero-Giiiza et al., 2014). However, when applying UDDT-FS as the sole substrate, the application of AD for the treatment of FS has been limited by unsatisfactory pathogen inactivation (Chaggu, 2004; Dudley et al, 1980; Foliguet & Doncoeur, 1972; Leclerc & Brouzes, 1973; McKinney et al, 1958; Plainer et al., 1950) in addition to low methane production (Fagbohungbe et al., 2015; Rajagopal et al., 2013). Microbiological safety of the liquid digestate and/or treated sludge is essential, especially when reuse of the treated matter for agricultural purposes is considered (Avery et al, 2014), as it can lead to transmission of enteric diseases (Pennington, 2001; Smith et al, 2005). These human health risks are also of concern when disposal to the environment is considered. As such, in our study, Chapter 3, 4, and 5 explored enhanced pathogen inactivation and biochemical energy recovery during anaerobic stabilisation of FS.