Recent UASB-pilot plant and full scale experiences show that anaerobic pre-treatment is feasible for sewage and domestic wastewaters in tropical regions. This offers developing countries the unique opportunity to become completely self-sufficient in this respect. UASB-systems can be applied at very small and at very big scale, i.e. for off-site and (house and community) on-site treatment. Results obtained in pilot plant and full scale installations demonstrate that these systems are quite effective in removing and stabilizing organic pollutants at liquid detention times as low as 4 hrs, i.e. a BOD reduction up to 75-95 % can be achieved, while an almost complete treatment can be accomplished by combining the method with a small aerobic lagoon. Instead of consuming high grade energy, these systems produce energy. Moreover the excess sludge production is very low, while also the dewatering characteristics of the sludge are excellent.

The increasing scarcity of clean water sets the need for appropriate management of available water resources. Particularly regions suffering from a lack of water urgently need integrated environmental protection and resource conservation (EP and RC) technologies in order to enable effective management of the available water resources. EP and RC-concepts focus on pollution prevention and on a minimum of consumptive use of energy, chemicals, and water in pollution abatement and a maximum of re-use of treated wastewater, by-products and residues produced in the treatment of waste and wastewater. Consequently, by implementing these concepts, waste(water)s like sewage and industrial effluents become an important source of water, fertilisers, soil conditioners and (frequently) energy instead of a social threat. In addition, a bridge is made between environmental protection and agriculture practice, stimulating (urban) agriculture in the neighbourhood of large cities. Anaerobic treatment is considered as the core technology for mineralising organic compounds in waste(water) streams. Additional technologies are required to comply with the reuse criteria. Some examples of possible EP and RC concepts, using the anaerobic treatment technology for the reclamation of domestic sewage are discussed.

Urban slums in East Africa exhibit deplorable sanitary conditions. Despite (inter)national efforts, slum sanitation provision remains inadequate and the projected population growth forecasts a worsening of this crisis. The core of the problem is that available knowledge about the local feasibility of the currently applied sanitary methods is limited. This paper analyses the interface of sanitation policy and technology domains by reviewing the distribution and local characteristics of current centralized and decentralized sanitation options. The findings confirm that conventional, centralized sanitation is an unrealistic solution for application in slums. Simplified sewerage may prove appropriate, but the reported initiatives are in the planning phase only. At present, only decentralized sanitation options are found to be viable in the assessed slums, but their servicing is increasingly neglected by the municipal authorities. The quasi-monopoly of pit latrines implies that improved sanitation technologies are not sufficiently rooted yet. Public toilets are crucial to these slums, especially where land tenure issues prevail. Although the potential of ecological sanitation is currently negligible, novel biocenter initiatives are promising. Municipal authorities are advised to prioritize the implementation of elsewhere successful slum sanitation technologies and to integrate appropriate decentral solutions into their predominantly centralized sanitation schemes.

This paper reviews recent technological developments in the filtration of primary effluent. Various studies show that single stage intermittent sand filters attain removal efficiencies of 90% COD, 95% BOD5, 30% TN, 40% TP and 99-99.9% FC at maximum BOD5 loads of around 10 g.m−2.d−1 and hydraulic loads of 5-10 cm.d−1. The permissible organic load can be enhanced by measures such as improved aeration and the use of multilayer filters. Nitrogen removal can be enhanced to 70% by adding a C-source to the filter material or by using two-stage post- and pre-denitrification systems. High organic loading rates (up to around 100 g BOD5.m−2.d−1) are possible with aerated adsorbent foam as a medium.

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