Water SA

Prologue to the WISA 2008 Conference Special Edition

The Water Institute of Southern Africa (WISA) held its first conference in 1989 in Cape Town. The most recent and 10th Biennial WISA Conference was held in May 2008 at Sun City, South Africa. The WISA 2008 conference theme, 'Confluence of the Water Industry' set the scene for a wide range of presentations with regards to the South African water industry and research in related fields. In keeping with the conference theme this introduction provides a confluence of papers in this journal edition. A brief description of the paper selection procedure is included and each of the papers in this edition of the journal is purposefully referenced in this coherent text.

Application of a sustainability index for integrated urban water management in Southern African cities: case study comparison - Maputo and Hermanus

Poor service provision in developing countries, and particularly the provision of water-related services, present serious challenges to urban development. It is estimated that 300 m. people in Africa do not have access to safe drinking water and 313 m. have limited access to adequate sanitation. The critical situation in the water sector continues to undermine strategies for poverty eradication and retards development. It is possible that the failure in service provision can in part be attributed to an inability by policy makers to address urban water management in a holistic manner. In this study, a systems approach has been adopted to develop a composite index that could be used to assess the potential of a town or city to be sustainable. This index, the Sustainability Index for Integrated Urban Water Management (SIUWM) is composed of 5 components which disaggregate into 20 indicators and ultimately into 64 variables. Two Southern African urban centres, Hermanus and Maputo, were selected as initial case studies to test the applicability and validity of the index and to compare their sustainability index scores. Results of the SIUWM application demonstrate that the index could highlight areas for improvement and ultimately guide appropriate action and policy-making towards better service delivery and improved resource management.

Managing the unseen: Langebaan Road Aquifer System

The effective management of groundwater resources is a critical aspect to ensure sustainability. The paper discusses the structures used to ensure effective monitoring at a local government level, and focuses specifically on the process followed and the critical monitoring factors identified to ensure sustainability. The paper highlights specific problems experienced with the implementation of the Langebaan Road Aquifer well-field as an integrated water resource, and the interaction required between the different role players. Suggestions, based on the Langebaan case study, are made regarding the different aspects to be monitored and the institutional arrangements required, ensuring effective participation between National and Local Government and other affected parties. The paper concluded that an independent monitoring committee is of utmost importance to ensure the successful management of a sustainable groundwater resource. The lessons learned through the implementation of the Langebaan Road Aquifer proves that structured participation in the management of these resources is of critical importance and that success cannot be achieved without cooperation between all parties, in particular the different government departments.

Destratification induced by bubble plumes as a means to reduce evaporation from open impoundments

The use of thermal mixing by means of compressed air appears to have important potential for evaporation suppression on deep reservoirs. Current methods used to reduce evaporation from open-water impoundments such as floating covers, modular covers, monolayers and shade structures have many disadvantages and negative impacts on the environment. These methods impact the natural/modified aquatic ecosystem established in the dam; alter aesthetic qualities; increase the risk of dam failure in times of flood; could potentially lead to an oxygen reduction in the water; and may compromise the natural water treatment functions and operations such as the reduction of harmful bacteria, exposure to sunlight (form of disinfection) and natural and mechanical aeration thereby increasing treatment costs. The methodology proposed in this paper to help reduce evaporation losses from open-water impoundments, which indirectly addresses problems of water shortage and the associated economic impacts, involves the destratification of the water body using a bubble plume operated with minimal energy input to reduce surface water temperatures, with, a subsequent reduction in evaporation. The literature, although limited, indicates that this proposed method has merit and requires further research to identify specific reservoirs (size, depth, usage) that could benefit from such a destratification system. Evaporation suppression of as high as 30 % was achieved in some case studies.

Challenges facing the implementation of water demand management initiatives in Gauteng Province

Gauteng Province is the industrial heartland of South Africa and is one of the few large urbanised areas in the world that is not located adjacent to a major source of water. The demand for water in Gauteng outstripped the local resource of the Vaal River many years ago with the result that the area relies heavily on large water schemes which transfer water from adjacent river basins into the Vaal River basin. The water transfer schemes associated with the Vaal River basin are large by any international standards and the water resource system is one of the most complex and integrated anywhere in the world. As the demand for water continues to grow in Gauteng, the Department of Water Affairs and forestry is investigating the various alternative water resource development options as well as the potential for reducing the growth in demand through water conservation (WC) and water demand management (WDM) measures. From the most recent investigations it has become clear that WDM is no longer considered a possible option but rather a necessity that must be implemented as a matter of urgency. It has been established that even if new water resource development options are implemented, it will still be necessary to introduce the WDM measures. In this regard, several of the large municipalities in Gauteng have already commenced with various WDM interventions, some of which are already in operation and showing significant savings. The paper will highlight the need for WDM in Gauteng and provide details of the latest investigations into the potential savings that can be achieved. Some of the key problems that are hampering the implementation of WDM interventions in Gauteng will be discussed and the measures taken to overcome these difficulties will be explained. The benefits that can be obtained from a potent web-based data acquisition system which is already operational in several parts of Gauteng will also be highlighted. The paper concludes with the clear message that wasting water in Gauteng province is a luxury that cannot be sustained and measures to eliminate the wastage must be introduced as a priority before the situation deteriorates to such an extent that water shortages become a common occurrence.

The extent of non-compliant plumbing components used in South Africa

High quality plumbing components are essential to ensure the efficient and safe supply of water, and minimise water losses in buildings. South African legislation requires that all plumbing components installed comply with certain standards set by the South African Bureau of Standards (SABS). Water Services Authorities are responsible for enforcing this legislation, and are allowed to set their own additional requirements for plumbing components. This study investigated the extent of non-compliant plumbing components used in South Africa through a number of methods, and concludes that compliance is roughly 50%. This points to a large problem and has dire consequences for the future of effective water use and water leakage in South Africa. A worrying finding is that the level of non-compliance seems to be particularly large in low-cost housing developments. The main reasons for the low levels of compliance are a lack of enforcement at local government level and the fact that legislation does not prohibit the import and sale of non-compliant components. The paper makes a number of recommendations for improving the situation.

Evaluation of minimum residual pressure as design criterion for South African water distribution systems

The South African civil engineering fraternity has grown to accept 24 m as the design criterion for minimum residual pressure in water distribution systems. However, the theoretical peak demand in many systems has increased beyond the point where minimum residual pressure exceeds 24 m - at least according to hydraulic models. Additions of customers to existing supply systems have led to increased peak flows with time, often without infrastructure upgrades to internal reticulation. Increased flows imply reduced pressures. This is not necessarily a concern: peak flow conditions rarely occur in a supply system and also, customer complaints often act as a first sign of 'low pressures'. No complaints imply 'no low pressures'. The researchers analysed hydraulic models for 14 different towns in 5 municipal areas of South Africa, including 2 large metros, to identify the minimum residual pressures currently expected. The results include almost 55 000 model nodes and show that about 20% of the nodes in the distribution systems analysed have pressures of below 24 m, while pressures of below 14 m are not uncommon. Whether this relatively common occurrence of low pressures under modelled peak demand is found in practice is not known at this stage. A new guideline for minimum residual pressure based on previous criteria and results from this study is presented, noting that a physical lower limit of about 10 m water pressure is specified in home appliance specifications.

Particulate fingerprinting of water quality in the distribution system

Particles in the distribution system play an important role in the perception? Not clear what is meant) of drinking water quality, particularly in association with discolouration. In The Netherlands the water quality in the distribution system is traditionally monitored by turbidity measurements. However, turbidity is hard to quantify as it is a complex function of particle suspension, dependent on many factors. In this paper the value of on-line particle counting in determining the particulate volume load fed to and developing in a distribution system is discussed and analysed. On-line particle counters have been used at several locations in Dutch distribution systems to monitor the particulate water quality. Furthermore, particulate material in a transportation system was characterised by using pre-concentration methods allowing organic and inorganic analysis of the particulate material. By using on-line particle counters and pre-concentration methods, it is possible to identify different sources of particles in a distribution network. The overall conclusion of the authors is that on-line particle counters, in combination with pre-concentration methods, are very effective and useful tools in understanding the water quality processes in distribution systems.

Characterisation of natural organic matter (NOM) and its removal using cyclodextrin polyurethanes

Natural organic matter (NOM) occurs in all natural water sources when animal and plant material breaks down. NOM in water may react with chlorine and other disinfectants to produce disinfection by-products (DBPs), many of which are either carcinogenic or mutagenic. In this study the NOM content of the raw water from the Vaalkop Water Treatment Plant (which uses both chlorination and ozonation as treatment protocols) was characterised after fractionation on ion-exchange resins. Fractionation at different pH values resulted in the isolation of a neutral, a basic and an acidic component of either predominantly hydrophobic or hydrophilic NOM. In addition, NOM results from 3 open water bodies in Johannesburg were evaluated in the same manner. As expected, NOM from all water sources was predominantly hydrophobic (~60%). Each of the 6 isolated NOM fractions was percolated through synthetic cyclodextrin (CD) polyurethanes to determine the extent to which the CD polymers can remove NOM from water. The hydrophobic basic fraction and the hydrophilic acid fraction were most efficiently removed (24% and 10%, respectively). The remaining fractions were not much affected by the polymer treatment.

Full-scale trials of external nitrification on plastic media nitrifying trickling filter

The full-scale single-stage tertiary nitrifying trickling filter (NTF) at the Citrusdal Wastewater Treatment Plant provides for external nitrification of unclarified effluent from the facultative aerobic lagoon in order to meet standard effluent ammonia concentration requirements. The apparent ammonia nitrification rate (ApANR, gN/m² media surface·d) of the NTF was sensitive to particulate organic loading rates which were predominantly in the form of algae, and the soluble COD removal rates increased under cold climates. Installation of forced-air ventilation fans improved the nitrification efficiency from 15% to 43%. An increase in hydraulic loading rate (HLR) by effluent recirculation significantly improved the ApANR, eradicated filter flies and decreased the prevalence of worms. Maximum ApANR of ~1.0 gN/m²·d was achieved yielding an ammonia- removal efficiency of approximately 71%. Profile samples collected along the NTF media depth indicated poor media wetting at low HLR resulting in low ApANR (<0.5 gN/m²·d). Also during the cold and rainy winter period, poor biofilm activity and prevalence of motile algae were observed, and under low hydraulic loading rates and warmer temperatures, a dominance of filter flies and fly larvae were observed. In contrast, in controlled laboratory studies, ApANRs up to 1.72 gN/m²·d (22.1 mgN/ℓ removal) were attained, which, in conformity with full-scale, was also found to be sensitive to hydraulic loading conditions.

**Assessment of Cryptosporidium in wastewater reuse for drinking water purposes: a case study for the city of Amsterdam, The Netherlands**

Wastewater reuse is becoming increasingly important for supplementing drinking water supply needs and/or to reduce costs in many communities around the world. However, wastewater reuse can result in a potential transmission route for infectious agents. Therefore, the occurrence of Cryptosporidium was assessed in a treatment plant geared for the production of drinking water from wastewater effluent and the results were compared to those on an existing typical drinking water treatment plant operated by Waternet, the water cycle company of Amsterdam, The Netherlands, and its surrounding areas. The assessment was done using Monte-Carlo simulation and probability density functions to determine the occurrence of Cryptosporidium in raw surface water and wastewater effluent and the removal in different treatment steps. From the research conducted, it was concluded that under normal conditions, drinking water that meets Dutch drinking water quality standards could also be produced from treated wastewater effluent. However, additional redundancy should be built in to meet the standards under extreme operating conditions.

Framework for assessing the viability of implementing dual water reticulation systems in South Africa

In many settlements across the world (e.g. Pimpama Coomera and Mawson Lakes - Australia, Hong Kong - China, Majuro - Marshall Islands, Tarawa - Kiribati, and Windhoek - Namibia), dual water reticulation systems have been implemented in response to increasing water demands and decreasing freshwater availability. A dual water reticulation system comprises separate pipes that supply different water qualities to the end consumer. A set of pipes supply potable water while another set of pipes supply non-potable water. The non-potable water is targeted at meeting water requirements traditionally met using potable water (e.g. toilet and urinal flushing, landscaping irrigation, and industrial cooling). This therefore frees potable water to be used for previously unmet or increasing potable water requirements. For several reasons including the dearth of relevant national regulatory and guideline documents, consumer and decision-maker perceptions, ignorance, and appropriate decision-making tools, the use of dual water reticulation systems in South Africa has been limited. The aim of this study was therefore to develop a decision-making framework, using robust criteria, for assessing the viability of implementing dual systems in South Africa. This aim was achieved through undertaking literature reviews on the subject, an investigation of non-potable water consumers' and decision-makers' perceptions using questionnaires, and the actual development of a framework using data obtained from the literature review and questionnaires. The questionnaires were developed using seven key issues i.e. public health and safety, economics, technical feasibility, legislation/regulations and guidelines, organisational capacity, social acceptance, and public education. The various aspects of the Triple Bottom Line of sustainability (i.e. economic, environmental and social) provided structure to the framework while the Triple Bottom Line approach was utilised in the assessment of the different criteria.

Laboratory protocols for testing the efficacy of commercial pit latrine additives

There is considerable national interest in the use of commercial microbially derived products for controlling the rate of accumulation of the contents of pit latrines. Manufacturers claim that some of these products can reduce accumulation rates, prevent the pit from ever filling up, or even result in decreases in pit contents volume. Prior to this research, there have been no scientific publications that have conclusively supported or refuted these claims. This project undertook to perform reproducible laboratory tests that would quantify the effect of commercial pit latrine additive products. Protocols were developed and tested on a range of different commercial products sold for their ability to control the rate of accumulation of pit latrine contents. The effect of commercial additives on mass loss from VIP sludge in 300 g honey jars was compared to mass loss from similar units subjected to no treatment and treatment with water. The purpose of these experiments was to separate and quantify the effect of micro-organisms or enzymes originating from commercial pit latrine additives from the effect of natural processes within the pit latrine sludge (including digestion by micro-organisms in the VIP sludge and dehydration) and the effects of other actions associated with treatment, such as the addition of water. Results indicated that insignificant mass loss occurred in all anaerobic test units, while significant mass loss occurred in all other test units. However, there was no statistically significant difference between any of the different treatments in the aerobic units. Investigation of analytical data from the test units indicated that mass loss in aerobic units was due to a combination of dehydration through evaporation of moisture and biological stabilisation processes, and that the latter were not significantly enhanced by the addition of commercial pit latrine products. It was concluded that there was no evidence to support claims that pit latrine additives could extend the life of a pit latrine.