As fresh water is becoming progressively scarce due to increasing demand, as a result of high population growth, rapid economic development and climate change, and stricter regulations on wastewater discharge are set, world-wide the interest in water reclamation increases. The potential for resource recovery from wastewater and sludge is largely untapped and in developing countries, and in particular in Sub-Saharan Africa (SSA), only a small portion of these waste streams is used in a planned and safe manner.
Compared to surface water, reclaimed wastewater can also be an attractive source to increase water availability, because of the low fluctuations of flow and water quality and its abundance in the urban environment. Recognizing the many applications and benefits of water reclamation, the purpose of this thesis was to evaluate the potential of water reclamation for industrial use with Maputo as case study.
First a review was performed to provide a frame of reference for the trends in water reclamation for industrial use, the effluent quality and the degree of reliability that may be required, and to identify challenges and impediments to implementation. The findings of this review showed that although some examples of water reclamation implementation for industrial use exist, the region is challenged by the need to develop a framework that can facilitate the integration of social and technological methodologies and help to introduce water reclamation in water allocation planning, including the development of specific legislation for industrial water use and disposal in countries where it is not practiced as in the case of Mozambique.
Second, a framework for assessment of water reclamation for industrial use potential was developed and tested for the case of Maputo. It was found that Maputo, amongst others, requires changes in the sanitation infrastructure to increase the sewerage system coverage, a larger gap between drinking water demand and supply, legislation that encourages the use of reclaimed water by industries (incentives), and a higher technological capability to successfully implement water reclamation projects.
Third, a pilot test on the use of wastewater treatment plant (WWTP) effluent for unreinforced concrete production for the construction industry showed that the compressive strength of blocks manufactured using WWTP effluent had a similar strength to the blocks produced using drinking water. Ammonium, phosphate (impurities found in the WWTP effluent) and chlorine (added for disinfection) were found not to have a negative effect on the strength of the blocks. Water absorption tests confirmed the results of the compressive strength, as lower humidity was found in cases of higher strength.
Fourth, the development of a novel application of ceramic microfiltration treatment, focusing on hardness removal of model WWTP effluent for recirculating cooling systems make-up water indicated that softening can be combined with ceramic microfiltration for post-treatment of secondarily treated wastewater for use in cooling systems. The study also demonstrated that inhibition of calcium carbonate precipitation occurred when inorganic substances, such as phosphate, and organic compounds were present in the water, while the fouling of the membranes, due to sodium alginate in water, was only slightly negatively affected when combined with softening.
The thesis ends with the conclusion that the city of Maputo has potential for introducing water reclamation in industries, requiring well-planned interventions that include the opportunity of optimizing the use of water in different industries and institutions existent in the city and the vicinity. We have demonstrated that the central WWTP of Maputo could be used to supply water for cooling systems at a thermal power plant and construction industries, located nearby. To turn it possible, participatory and collaborative practices of the co-creation concept should be explored together with pilot studies, governance capacity evaluation and promotion of public private partnerships.