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Ncube E.J.,RSA Inc | Mohotsi M.,Rand Water
14th Water Distribution Systems Analysis Conference 2012, WDSA 2012 | Year: 2012

To maintain microbial quality, a distribution network should be designed and operated to prevent ingress of contaminants, to keep disinfectant residual concentrations within a locally predetermined range and to minimize the transit time (or age of the water after leaving the treatment works). With this in mind a study to determine the relationship between Standard Plate Counts (SPCs) and disinfectant residual in the distribution network was conducted. Data was extracted from an SQL database using Crystal reports application which is a business object tool. The statistics was calculated using the tool. The graphs were drawn using excel for simplicity purposes. This is used to identify relationships in the trend between the two parameters. The trend indicates some relationship between SPCs and chlorine in terms of compliance. The other parameters (E.coli, dissolved organic carbon (DOC) and turbidity were constantly in the region above 95% compliance except for chlorine, SPC and Total Coliforms (TCs). It was observed that a drop in the chlorine compliance results in a drop in SPC compliance. This is indicative of a relationship between the two parameters. However, this does not exclude any further impact that other parameters may have on this relationship. Copyright © (2012) by Engineers Australia.


Muzi Sibiya S.,Rand Water
Procedia Engineering | Year: 2014

A streaming current detector (SCD) is an instrument for measuring the charge that exists on small, suspended particles in water. The SCD is the instrument that can be used to measure coagulated particle stability for the feedback control of coagulant dosage. This report discusses the application of SCD as an instrument for coagulation dosage control. The SCD with automatic control of coagulant dosage consistently produced acceptable water quality, even during periods of changing raw water turbidity and varying flow rates. It minimizes under and overdosing of coagulant. It requires regular cleaning and maintenance to ensure optimum operation. The SCD is no substitute for efficient water treatment management. © 2013 The Authors.


Ramphal S.R.,Rand Water | Sibiya M.S.,Rand Water
Drinking Water Engineering and Science | Year: 2014

The size and structural characteristics of floc particles are important design and control parameters in water treatment and should be rapidly monitored with a reasonable amount of accuracy. In this study, a photometric dispersion analyser (PDA) coupled to standard jar test experiments was used to optimize coagulation-flocculation parameters while monitoring floc size and structure as well as the rate of floc formation during coagulation using alum. The optimal coagulation conditions were as follows: sample pH 8; alum dosage, 3 mg L1 as Al3+G value, 172 s1; rapid mixing time, 20 s. These conditions resulted in unstable treated water having a calcium carbonate precipitation potential (CCPP) of g15 mg L1 as CaCO3 and required a slaked lime dosage of 17 mg L1 as CaCO3 to equilibrate CCPP to acceptable levels. PDA data revealed that aggregation rate and steady-state variance are primary parameters as both have substantial influence on coagulation-flocculation efficiency. However, the average steady state ratio, although an important parameter, had a lessened impact on coagulation-flocculation efficiency. The results of this study showed that the PDA instrument is an important tool in coagulation kinetic studies and can be employed as an additional tool in the optimization of coagulation conditions. © 2014 Author(s).


Fadal M.F.,University of Johannesburg | Haarhoff J.,University of Johannesburg | Marais S.,Rand Water
Drinking Water Engineering and Science | Year: 2012

This paper proposes a three-parameter mathematical model to describe the particle size distribution in a water sample. The proposed model offers some conceptual advantages over two other models reported on previously, and also provides a better fit to the particle counting data obtained from 321 water samples taken over three years at a large South African drinking water supplier. Using the data from raw water samples taken from a moderately turbid, large surface impoundment, as well as samples from the same water after treatment, typical ranges of the model parameters are presented for both raw and treated water. Once calibrated, the model allows the calculation and comparison of total particle number and volumes over any randomly selected size interval of interest. © 2009 Author(s).


Sigudu M.V.,Rand Water | du Preez H.H.,Rand Water | du Preez H.H.,University of Johannesburg | Retief F.,North West University South Africa
Water SA | Year: 2014

Despite the health risks associated with exposure to Cryptosporidium and Giardia, there is no uniform approach to monitoring these protozoan parasites across the world. In the present study, a strategy for monitoring Cryptosporidium and Giardia in drinking water was developed in an effort to ensure that the risk of exposure to these organisms and the risks of non-compliance to guidelines are reduced. The methodology developed will be applicable to all water supply systems irrespective of size and complexity of the purification works. It is based on monitoring procedures proposed by the US Environmental Protection Agency, the Drinking Water Inspectorate, Australia and New Zealand, as well as the risk-based procedure followed by Northern Ireland. The monitoring strategy developed represents a preventative approach for proactively monitoring Cryptosporidium and Giardia species in drinking water. The strategy consists of 10 steps: (i) assessment of the monitoring requirements, (ii) description and characterisation of the source water types, (iii) abstraction of source water, (iv) assessment of the water purification plant, (v) water quality monitoring, (vi) cryptosporidiosis and giardiasis outbreak, (vii) risk assessment, (viii) sample collection and laboratory processing, (ix) data evaluation, interpretation and storage, (x) process evaluation and review. Proper implementation of this protocol can contribute to the protection of drinking water consumers by identifying high-risk source water, identifying areas of improvement within the water treatment system, and also preventing further faecal pollution in the catchments. The protocol can also be integrated into the Water Safety Plans to optimise compliance. Furthermore, this methodology has a potential to contribute to Blue Drop certification as it should form part of the incident management protocols which are a requirement of Water Safety Plan implementation.

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