Jedjan Siriwong, Pawit Chaivisit, and Sumeth Chaiprapat

pp. 553 - 563

Abstract

         Assessment of efficiency of water production system in Prince of Songkla University, Hat Yai Campus, was conducted in this study. Topics covered include 1) quality and quantity of raw water, 2) water production process, 3) management and maintenance of water production system, and 4) quality of finished water.
Totally, 494 water samples were collected during the study. All water samples were analyzed for turbidity, pH, temperature, conductivity, TDS, total coliforms, fecal coliforms and residual chlorine. In addition to the mentioned parameters, 30 of these water samples were also analyzed for hardness, chloride, nitratenitrogen, sulfate and heavy metals (manganese, copper, zinc, iron, chromium, cadmium, lead and mercury). All water samples were collected during November, 2004 (rainy season) and March, 2005 (summer season).
          It was found that the quality of the water in the Sritrang reservoir fell into Class 2 of Thailand Surface Water Quality Standard that requires ordinary water treatment processes prior to consumptions Cadmium, lead and mercury were not detected by Inductively Coupled Plasma (ICP) method. There are 2 sets of water production system. The first set consists of 4 pressure filters which could reduce turbidity at varying efficiencies: 33.83%, 18.26%, 42.76% and 65.67% depending mainly on the extent of chemical dosing control and the maintenance of the filter media. Another system employed sedimentation tank and rapid sand filter, which could remove turbidity at 89.28%. When combined finished water from both systems were analyzed, it was found that removals of manganese, copper, zinc, iron and chromium were 42.65%, 30.02%, 19.54%, 56.82% and 15.12%, respectively. Residual chlorine concentration of the finished water was not more than 0.2 mg/L and no total coliforms or fecal coliforms were detected. The plant had sufficient and competent personnel to carry out their normal tasks but occasional negligence and lack of specific water testing or chemical dosing equipment were observed. The quality of tap water (in distribution system) is
in compliance with the WHO drinking water quality standards, except occasionally turbidity and pH. Significant difference (p<0.05) in tap water quality was found between the samples collected in rainy and summer seasons.