Water Journal : Water Journal August 2015
AUGUST 2015 water 43 Feature article and disinfection prior to being returned to the main storage facility, the Garden Route Dam, where it is combined with current raw water supplies. This initiative augments the existing supply by 10 ML/ day, approximately one-third of the drinking water demand. Final effluent from the WWTW is treated by drum screen, ultrafiltration and chlorination. Provision has been made for powdered activated carbon addition at George WTW, if required as an additional operational barrier. The product water delivered is of equivalent quality to Garden Route Dam water. Beaufort West: 2.3 ML/day DPR Plant (2010) The town of Beaufort West shows a significant population growth due to increasing economic activities. The local municipality initialised a project to supply additional SANS241-1:2011 standard water as a result of a shortage of drinking water. The proposed solution for this problem was to build a plant for the reclamation of WWTW product water to deliver potable water. The reclamation plant is maintained and operated by Water and Wastewater Engineering in a 20-year agreement. The process implemented follows the multi-barrier concept: final effluent from WWTW, sand filtration, UF, two-stage RO, with permeate disinfected by ultraviolet light. The product water quality exceeds the national standard for potable water. Port Elizabeth (Nelson Mandela Bay Municipality): 45 ML/day Membrane Bio Reactor (MBR) Industrial Re-use Port Elizabeth is a major development centre. The growth of industries and subsequent population growth creates an increased demand for water. The area is also currently affected by severe drought conditions, which place tremendous stress on existing surface water resources. The municipality and Royal HaskoningDHV are upgrading the existing Fishwater Flats WWTW to 170 ML/d. Planning and design are underway to provide advanced treatment in the form of MBRs and RO to supplement the existing water resources and provide industrial and potable water through indirect re-use. The first phase of the water re-use scheme will produce 45 ML/day, which will be suitable for industrial and/or IPR, with a second phase of similar capacity to follow. Hermanus: 5 ML/day DPR Plant Drought conditions have resulted in a shortage of drinking water in the town of Hermanus. Reclamation of effluent for DPR was selected to augment the existing surface water supply. The first phase of the project entails the construction of works to re-use 2.5 ML/day of effluent with civil works for a future increase in capacity to 5 ML/day. The process train uses UF pre-treatment and RO desalination, as well as advanced oxidation and carbon filtration, and the water quality exceeds SAN241. The product from the re-use plant will be fed directly into the drinking water reticulation system. Emalahleni: 50 ML/d plus 15 ML/d, IPR The town of Emalahleni is served by two full-scale, operational mine water-to-potable supply plants: Optimum Water Reclamation Plant (OWRP) and eMalahleni Water Reclamation Plant (EWRP). The plants are operated by Anglo American Thermal Coal, 32South (formerly BHP Billiton), and Glencore (formerly Optimum Coal). The water is blended for IPR supplies to the local municipality. The town of 510,000 people is the energy hub of the country, providing 70 per cent of South Africa’s electricity generation, and is dominated by mining, steel, power and agriculture. Its main water source is Witbank Dam (capacity ~104 billion litres). The EWRP was first commissioned in October 2007 with establishment capital of R1.4 billion (US$175m) and a plant capacity of 30 ML/day treated water; expansion to 50 ML/day took place in 2011. The 15 ML/day OWRP assists the mine to operate successfully and to mitigate its impact on the downstream environment. Construction commenced in October 2008 and the facility was commissioned in September 2011. The total capital spend was R545m. The process trains in both WRPs include neutralisation followed by UF, RO and chlorination. recent research The majority of research over the past decade has investigated greater efficiency in the engineering or scientific aspects of product water quality. Decision-support model for the selection and costing of direct potable re-use systems from municipal wastewater Water supply authorities face challenges when diversifying the mix of raw water resources they use to provide potable supplies. Numerous options are available when planners want to improve water surety (and sustainability) or make provision for drought periods. Sufficient information is often not readily available for the planners or local authorities to make informed selection of the best options for a specific situation, especially regarding technical, costing, energy and environmental data. Even if the information is obtained, comparison of the best possible options is often not feasible, because of the differences in priorities assigned to the multitude of factors making up the main components of the selection criteria. Swartz et al. (2014)4 created a decision-support system to be used to identify, evaluate, compare and select appropriate options that can be used to produce sufficient quantities of safe drinking water from available water sources. The guide also included the development of a re-use costing model, REUSECOST, and REUSEDSM, a spreadsheet- based decision support system was developed to provide a simplistic method to compare different re-use options using multi-criteria analysis. This model focused on DPR as a water-supply option to augment conventional water source in water scarce areas. Wastewater reclamation for potable re-use The main objective of this research5,6 by Umgeni Water (a water board in the east of the country) was to evaluate the performance of different MBRs as a pre- treatment step to produce potable water. Three MBR pilot plants were set up at a WWTW in Durban. Settled sewage was supplied to each pilot plant via a common balancing tank. The three plants utilised different Optimum Water Reclamation Plant (OWRP). eMalahleni Water Reclamation Plant (EWRP). 4 CD Swartz, CJ Coomans, HP Muller, JA du Plessis and W Kamish: Decision-Support Model for the Selection and Costing of Direct Potable Reuse Systems from Municipal Wastewater, Research Report No. 2119/1/14 Water Research Commission, Pretoria, South Africa, 2014. Available online at www.wrc.org.za/Pages/ DisplayItem.aspx?ItemID=10780&FromURL=%2fPages%2fKH_AdvancedSearch.aspx%3fdt%3d1%26ms%3d%26d%3dDecision-support+model+for+the+selecti on+and+costing+of+direct+potable+reuse+systems+from+municipal+wastewater%26start%3d1.
Water Journal June 2015
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