AWWA WQTC64095

A variety of risk analysis methodologies are available to assess the risks experienced in differentdisciplines. However, determining the probability that a properly operated water treatment plantwill produce water that is not compliant with a stated threshold presents a unique challengebecause of both the complicated nature of water treatment and the natural variation of waterquality and quantity.One methodology that could be used is the consequence frequency assessment (CFA), which isused in microbial risk assessment. In this research, a full-scale anthracite/sand filter unit wasanalyzed using the CFA, based on the influent and effluent turbidity. The risk output from theconsequence frequency assessment showed some deficiencies including a possibleoverestimation of the risk of producing high turbidity water and an inability to incorporate morethan one regulated parameter.The difficulties of using the consequence frequency assessment called for a different approach toperform the analysis. The approach used in this research combines water treatment plantmodelling with probabilistic risk analysis. To compare the two methods, the same filtration unitthat was analyzed using the consequence frequency assessment was then analyzed using the newmethodology.As an example of results obtained, the consequence frequency assessment determined that theprobability of producing effluent turbidity greater than 0.30 NTU was 1.0% while the probabilityof producing effluent turbidity greater than 0.10 NTU was 10%. The new methodologydetermined that the probability of producing effluent turbidity greater than 0.30 NTU was 0.6%while the probability of producing effluent turbidity greater than 0.10 NTU was 0.7%. Alongwith the numerical difference between the methodologies, the new method can deal with theproblems experienced while using the consequence frequency assessment and incorporatemultiple regulated parameters into the analysis.The demonstrated disparity between the results obtained with the two risk analysismethodologies shows the potentially significant role that an analysis methodology can play in theanalysis results. This potential disparity is important for water utilities, regulators and riskassessors since it shows that the analysis methodology could potentially be an important factorinfluencing decisions, including capital works, that are made based upon risk analysis results. Includes 21 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

13

File Size:

1 file , 350 KB