The current challenges facing the provision of sanitation services to the poor are explained in terms of the MDGs, rigid discharge standards, increasing water stress, intermittent energy supply are outlined. They are contrasted with future responses and objectives such as sustainability targets, risk based approaches to the setting of effluent limits, the emphasis on water conservation, food security and the acknowledgement of excreta as a resource. In spite of these secondary objective it must be noted that the primary reason for sanitation systems is public health. The main pathogen load is in excreta which is traditionally dispersed in many times its mass of water. The large numbers of peoples to be served implies that the systems need to be standardized, prefabricated and to be capable of integrating into an upgrade trajectory. This implies that although the systems must be inexpensive, the technology which is used to developing the systems must be sophisticated. The upgrade trajectory needs to take into account aspects such as low flows, separated waste streams (source separation), the beneficial use of the components in excreta (possibly in agriculture) and the use of low energy processes - possibly to be even a net energy producer.
Research challenges will include the splitting of streams so as to promote better treatment or reuse; the development of low pressure (or gravity driven) membrane systems and the integration of constructed wetlands and agricultural systems into the treatment process. The streams will become much more concentrated so that reactor design more sophisticated.
The DEWATS system which consisting of an anaerobic baffled reactor followed by an anaerobic filter which feeds into a constructed wetland and incorporating gravity membrane filtration will provide different qualities of treated wastewater for use in horticulture. The inclusion of source separation will provide additional cost savings and agricultural benefits.
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