Basic Math Concepts for Water and Wastewater Operators

INTRODUCTION Purpose of Good Practice Guide The catchment-to-consumer risk-based approach to the production of microbially-safe drinking water, which is detailed in the Framework for Management of Drinking Water Quality (the Framework) that underpins the Australian Drinking Water Guidelines (ADWG), is based on the identification and control of risks to the quality of drinking water supplied to consumers. This reduction in risk is achieved by implementing a multiple barrier approach, where a number of different barriers to contamination are put in place, from the catchment to the consumer. Whilst the risk management process stretches all the way from catchment to consumer, in practice the majority of risks are managed through the use of various water treatment processes. Most Australian source waters require some level of treatment prior to being supplied to consumersas drinking water. The level of treatment required to produce microbially-safe drinking water will be a function of the quality of the source water and should be informed by a system-specific risk assessment process that is consistent with the approach described under Element 2 (Assessment of the drinking water supply system) of the Framework. The production of microbially-safe drinking water is difficult to consistently achieve, and requires constant vigilance, as well as well-maintained and operated water treatment processes (Element 3 (Preventive measures for drinking water quality management) and Element 4 (Operational procedures and process control) of the Framework). Within this risk-based approach, the purpose of this Guide is to provide concise advice on good practice preventive measures for the management of drinking water treatment processes and the distribution of this treated water to consumers. This is achieved by providing targets, both numerical and observational, for the various activities that should be undertaken in order to produce microbiallysafe drinking water. The Guide is not intended to be a risk assessment tool; it assumes that a system-specific risk assessment has been done, and that the treatment and distribution processes that are present are suitable for the assessed level of microbial risk. The Guide is therefore focused on the optimisation, management and control of existing water supply systems. The advice in this Guide is applicable to existing water supply systems and is intended to help water utilities produce microbially-safe drinking water under existing arrangements; it will also assist utilities meet any future microbial health-based targets that may be includes in the ADWG. The Guide is presented in a tabular format for simplicity. The table is broken into sections that relate to the key control points in typical water treatment and distribution systems.

Abstract: This work describes how the design and operation parameters of the Multi-Stage Flash (MSF) desalination process are optimised when the process is subject to variation in seawater temperature, fouling and freshwater demand throughout the day. A simple polynomial based dynamic seawater temperature and variable freshwater demand correlations are developed based on actual data which are incorporated in the MSF mathematical model using gPROMS models builder 3.0.3. In addition, a fouling model based on stage temperature is considered. The fouling and the effect of noncondensable gases are incorporated into the calculation of overall heat transfer co-efficient for condensers. Finally, an optimisation problem is developed where the total daily operating cost of the MSF process is minimised by optimising the design (no of stages) and the operating (seawater rejected flowrate and brine recycle flowrate) parameters.