IAS Fellow's Seminar

Fellow: Muhammad Saidam

Chair: Colin Bain

Title: Reducing Uncertainty in Assessing Water Quality

The theme of this seminar is the issue of uncertainty in the identification of certain biological and chemical contaminants in surface water and how this uncertainty should be reflected when laboratory results are translated into information targeting decision makers and the public. This is particularly significant when a pollution incident is suspected and stoppage of water supply is considered. Such a decision becomes more critical in the absence of a readily available alternative source of water supply.

Large part of this uncertainty stems from the complexity of collecting a representative water sample. Particularly when samples are collected for the analysis of contaminants whose distribution in the water body is highly variable and whose occurrence is in low numbers (e.g. cryptosporidium) or in micro concentrations (e.g. chlorinated hydrocarbons). Collected water samples, grab or even composite, can hardly be called representative of the water column in such cases. This can greatly affect our confidence when interpreting the results to turn them into practical and useful information for water management and building public trust. These contaminants, nonetheless, can cause serious negative health impacts. Cryptosporidium has been blamed for the occurrence of several outbreaks of gastrointestinal illnesses in several developed and undeveloped countries.

This research focuses on studying a sampling method to improve the chances of identifying these micro- contaminants. Suspended and colloidal solids were captured by means of a small settling chamber installed at the bank of a river through which river water was made to pass. Contaminants, which couldn't be detected in grab or composite water samples, were identified in the settled matter samples obtained from the settling chambers. These samples constitute a much better representation of the water column compared with water samples. This reduces uncertainty and increases confidence in the interpretation of results. It also provides a better basis for judgment regarding the presence of these micro-contaminants and thus enables more decisive reporting to decision makers and the public.

Points for discussion:

1. Viability of the sampling technique as a basis for identification and risk assessment of micro-contaminants, particularly cryptosporidium?
2. How much of the uncertainty should be reflected in translating the analytical results into information to decision makers and the public?
3. Practical and ethical considerations in translating laboratory results into information bearing in mind a certain degree of uncertainty?