OCR Text |
Show PART II PRESENT STATUS Disinfection Is used to kill pathogenic organisms that cause water- borne disease. Disinfection alone may be adequate treatment for ground- water depending on the quality of the supply; however, it generally is not adequate treatment for surface water supplies. The extent of water treatment necessary in a municipal system is dependent upon the water quality of the source of supply. High concen- trations of dissolved solids are present in many of the groundwater and surface water sources of the Region. Some municipalities are utilizing water in which the dissolved solids concentration exceeds 500 mg/1 the recommended limit of the Public Health Service Drinking Water Standards of 1962. In the absence of water of better quality, persons often adjust to water containing substantially higher concentrations of dissolved minerals. Adherence to the drinking standards would restrict domestic use of surface and ground supplies in many parts of the three subregions. Hardness in water (as CaC03) associated with dissolved solids is present in significant concentrations at lower elevations and generally exceeds 120 mg/1. Various water softening processes can be used, either at the municipal treatment plant or on an individual water user basis. Water softening at municipal water treatment plants is not prevalent in the Region. Other chemical paraments such as chlorides, sulfates, nitrates and fluorides do not present widespread Regional problems. There are isolated areas where high concentrations of these chemicals are of concern. 1/ Various heavy metals such as iron, manganese, arsenic and cyanide are present in excessive concentrations in source waters being used by some municipalities. Removal of these elements will require additional treatment processes at additional cost. The presence of pathogenic bateria and viruses in municipal source waters does not appear to be a significant Regional problem. Occasional isolated problems do occur. For this reason disinfection should be considered a minimum public health safeguard against the chance of bacterial or viral contamination of groundwater supplies; and coagulation, sedimentation, filtration, and disinfection should be the minimum public health safeguard against the chance of bacterial or viral contamination of surface water supplies. For a more thorough and detailed evaluation of drinking water quality, the reader is referred to a section entitled, "Drinking Water Supply," Part IV of the Water Quality, Pollution Control and Health Factors Appendix. 1/ Refer to Water Quality, Pollution Control and Health Factors Appendix. 25 |