Applying an abbreviated hazard analysis and critical control point programme to evaluate the effectiveness of two potable water treatment systems to remove health-related contaminants

Abstract

The abbreviated HACCP (Hazard Analysis and Critical Control Point) programme applied in this study comprised mostly of a health-related microbiological hazard analysis together with the use of critical performance limit targets (CPL Ts) to assess the effectiveness of treatment system components at two drinking water treatment facilities. The hazard analysis was based on the occurrence of total coliforms and faecal coliforms, both of which are health-related microbiological indicator organism groups. Turbidity was used to assess the effectiveness of the treatment components to produce quality of drinking water that would comply with national water quality guidelines. Turbidity testing was also included in this study to augment microbiological hazard analyses with the understanding that if turbidity levels were reduced to sufficient levels, microorganisms would also be reduced - an approach which could have offered the treatment facility manager a quick test option in lieu of microbiological testing. The raw river water used for drinking water treatment at both treatment facilities complied with the raw water extraction guidelines proposed for this study. The same was observed of the treated end-product, namely treated potable water. The end product complied with national health-related drinking water guidelines, which indicated that the designs of the selected treatment facilities were well planned and managed. To determine the effectiveness of the treatment components (known as critical control points (CCPs)), a set of critical performance limit targets (CPL Ts) was compiled for this study since such targets were not available at the treatment facilities. The premise was that if the CCP complied with the CPL T, the process was effective and thus functioning properly. Most of the health-related indicator results complied with the target CPL Ts. When comparing sedimentation from both treatment facilities, it appeared that this process within the Mazelspoort treatment faci lity functioned more effectively in reducing the health-related indicator levels than the sedimentation process at the Rustfontein treatment facility. The CPL T for sedimentation is 90% removal for the microbiological indicators and 85% removal for turbidity. Sedimentation at the Rustfontein treatment facility could not reduce any of the indicators used in this study to comply with the CPL Ts. It reduced only 87% of the total coliforms, 89% of the faecal coliforms and 45% of turbidity received from the raw water extraction point. The filters at the Rustfontein treatment facility under-achieved in the reduction of the indicator organisms, while the filters at Mazelspoort seemed to perform effectively with only occasional under-achievement in the reduction of faecal coliforms. The filters at the Rustfontein treatment facility failed to reduce the numbers of total coliforms to the required CPL T. They only reduced 41% (CPL T of 99%) of the total coliform load received from sedimentation, placing pressure on the chlorination stage to reduce the remaining organisms. Chlorination reduced the numbers of all the indicators to acceptable limits. Although some critical control points at these treatment facilities could face difficulties in controlling these healthrelated risks, these facilities could be perceived as effective in treating the raw river water to a high quality potable water to be distributed to the public. Weak correlations were found between the occurrence of the health-related indicator organisms and turbidity. The assumption could therefore be made that turbidity should not be used as a solitary indicator of process effectiveness. Additional microbiological and possibly additional chemical quality tests should be considered as monitoring procedures to manage a water treatment facility effectively.