Direct drinking water reclamation from the Goreangab reclamation plant, has been a reality in Windhoek, Namibia since 1968. Potable reclamation is a fixed part of the water supply and waste water has become an indispensible resource for the survival and continued growth of the city. The multi barrier concepts that were applied 40 years ago have been refined over many years. Improvements in water treatment technology have made it possible to improve the reliability and the drinking water quality of the reclamation treatment process. With the latest upgrade, which was designed 14 years ago and commissioned in 2002, a specific design philosophy was followed. This paper will assess whether the objectives of the design philosophy have been met in terms of removal efficiencies and safety of drinking water, which contains at present 25% reclaimed water. The basis and aims of the multi barrier design that was applied is discussed and with the aid of natural organic matter (NOM) and microorganism removal, the reliability of the philosophy is tested and compared with the goals set. Comparisons are drawn between the new plant and the previous plant and how the new plant is able to accommodate changes in raw water quality. It can be concluded that the water quality has been improved and the barrier principle does reduce the risk and improve the water quality.
Australia has had Guidelines in place for water recycling (for all uses other than the augmentation of drinking water supplies) since 2006. These Guidelines were extended to cover potable reuse in May 2008 and have been applied to two potable reuse projects in Australia -one a trial plant in Perth, Western Australia and the second for a large AUD$2.6 × 10 9 scheme in Brisbane, Queensland. All reclamation plants in Australia must be 'validated' against the Australian Guidelines for WaterRecycling prior to being put into operation. The majority of advanced reuse schemes incorporate the dual membrane process -microfiltration or ultrafiltration followed by reverse osmosis (RO) -in the treatment trains and while this membrane based treatment has been shown to produce a very high quality of product water, it does come at a cost and there is renewed interest in alternative treatment technologies that offer cost savings and are more sustainable. This paper uses data gathered inAustralia from a range of advanced reclamation plants, as well as design and actual performance criteria from the Goreangab Plant, to 'validate' the latter and, given the longevity of the Windhoek direct potable reuse experience, lend support to more serious consideration of non-RO based plants for potable reuse applications.
Abstract. Organic pollution is a major concern during drinking water treatment. Major challenges attributed to organic pollution include the proliferation of pathogenic micro-organisms, prevalence of toxic and physiologically disruptive organic micropollutants, and quality deterioration in water distribution systems. A major component of organic pollution is natural organic matter (NOM). The operational mechanisms of most unit processes are well understood. However, their interaction with NOM is still the subject of scientific research. This paper takes the form of a metastudy to capture some of the experiences with NOM monitoring and analysis at a number of Southern African Water Treatment Plants. It is written from the perspective of practical process selection, to try and coax some pointers from the available data for the design of more detailed pilot work. NOM was tracked at six water treatment plants using dissolved organic carbon (DOC) measurements. Fractionation of the DOC based on biodegradability and molecular weight distribution was done at a water treatment plant in Namibia. A third fractionation technique using ion exchange resins was used to assess the impact of ozonation on DOC. DOC measurements alone did not give much insight into NOM evolution through the treatment train. The more detailed characterization techniques showed that different unit processes preferentially remove different NOM fractions. Therefore these techniques provide better information for process design and optimisation than the DOC measurement which is routinely done during full scale operation at these water treatment plants. Further work will focus on streamlining and improving the reproducibility of selected fractionation techniques, characterization of NOM from different water sources, and synthesis of the results into a systematic, practical guideline for process design and optimisation.
Organic pollution is a major concern during drinking water treatment. Major challenges attributed to organic pollution include the proliferation of pathogenic micro-organisms, prevalence of toxic and physiologically disruptive organic micro-pollutants, and quality deterioration in water distribution systems. A major component of organic pollution is natural organic matter (NOM). The operational mechanisms of most unit processes are well understood. However, their interaction with NOM is still the subject of scientific research. This paper takes the form of a meta-study to capture some of the experiences with NOM monitoring and analysis at a number of Southern African Water Treatment Plants. It is written from the perspective of practical process selection, to try and coax some pointers from the available data for the design of more detailed pilot work. NOM was tracked at six water treatment plants using dissolved organic carbon (DOC) measurements. Fractionation of the DOC based on biodegradability and molecular weight distribution was done at a water treatment plant in Namibia. A third fractionation technique using ion exchange resins was used to assess the impact of ozonation on DOC. DOC measurements alone did not give much insight into NOM evolution through the treatment train. The more detailed characterization techniques showed that different unit processes preferentially remove different NOM fractions. Therefore these techniques provide better information for process design and optimisation than the DOC measurement which is routinely done during full scale operation at these water treatment plants
This paper deals with the occurrence of Giardia and Cryptosporidium in the water sources available for the Goreangab Reclamation Plant (GRP) and the subsequent removal during treatment at the reclamation plant. Giardia is detected more often than Cryptosporidium. 60% of the time it is detected in the samples from the dam and in 55% of the samples from the maturation pond effluent. During the investigation, Giardia was detected in the final water 5% of the time and Cryptosporidium 2% of the time. The maximum Giardia cysts detected in a sample was 30, the 99% percentile was 20 and the 97% percentile 10 cysts. A maximum of 20 Cryptosporidium oocysts was detected in a sample. The 99% percentile counted 6.2 oocysts and the 97% percentile 0 oocysts. From the data presented it is clear that the polluted dam water has the same risk level of Giardia and Cryptosporidium pollution as treated wastewater effluent. This emphasises the fact that the sources should be monitored continuously for these parasites. The sporadic high counts of Giardia and Cryptosporidium in the raw water sources indicate that a multiple-barrier approach must be followed to ensure the safe operation of even conventional treatment plants using polluted source water. No correlation could be found between cyst and oocyst removal and other water quality parameters. The advocating of a final water turbidity of 0.1 NTU and the use of particle counters can only be supported by these findings, as it is possible to achieve a turbidity of less than 0.1 NTU at the sand filter outlet, even in a developing country like Namibia. The challenge lies with the maintenance of equipment and vigilance of the operators.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.