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Show alternative softening process. Table 3 is a summary of the conservation potential of several alternative measures. The level of conservation achieved by using an alternative softening process depends upon the process selected. For example, with lime softening, no conservation of process water is achieved. As mentioned previously, this process would only be feasible to replace home water softener units where surface water is the sole source of supply. But, the lime softening process improves the quality of the wastewater and its potential for reuse. TDS levels could be reduced by about 270 mg/ 1 ( 100 mg/ 1 hardness reduction and 170 mg/ 1 salt reduction), significantly improving the reusability of about one third of the total waste stream. Reverse osmosis wastes five times as much water ( 25,000 gallons per year per household) as ion- exchange to produce the same amount of water. Its conservation potential lies in reducing the TDS content of the entire wastewater stream by 170 mg/ 1. These savings may be nullified however, if ion- exchange softening is required as a pretreatment. Prohibition of water softeners altogether would provide the maximum level of conservation. Conversion to high efficiency softeners could potentially reduce water and salt consumption by 50 percent. Thus, 2,200 acre- ft of water would be saved and TDS would be reduced by 85 mg/ 1. The level of conservation achieved by prohibiting softeners only where water supplies are naturally soft would be relatively low. This is due to the small number of communities which have naturally soft water, and because the number of softener installations is directly proportional to the hardness of the water. Those areas with naturally soft water would have few installations. Water Quality Considerations The widespread use of household ion- exchange softeners has a significant impact on the state's water resources. It is most notable in the domestic wastewater stream since the disposal of waste from the regeneration cycle increases the salinity of wastewater. The concentration of salinity may affect the potential for wastewater reuse or the method of effluent disposal. To a lesser extent, water softeners impact water resources by consuming some water during the regeneration cycle of the ion- exchange process. The average softener uses about 4,800 gallons of water per year which equates to a statewide total of 3.9 mgd or 4,400 acre- ft per year. Until recently, wastewater has not been viewed as a valued resource. But this perception is changing as higher quality water sources reach their limits. An average of 150 gallons of wastewater is generated per person each day. Roughly 40 percent of the households in the state own a water softener and another 10 percent rent softeners. Assuming 500 pounds of salt usage per softener per year and a total state population of 1,886,000 ( or 598,730 households), it is estimated that softeners contribute almost 75,000 tons or 174 mg/ 1 of salt to the wastewater stream each year. In Utah, more than 268 million gallons of the wastewater produced each day is collected and treated at community water reclamation facilities. Much of this water is returned to groundwater aquifers or discharged to natural waterways, but many communities are beginning to investigate the potential to reuse the effluent. Since salinity may limit the potential of wastewater effluent for reuse, reducing the salt load of the waste stream will become increasingly important. Communities which currently have reuse programs include Heber City, Wasatch County; Blanding, San Juan County; Cedar City, Iron County; Roosevelt, Duchesne County; and Santaquin, Utah County. Even though the amount of TDS contributed to the waste stream by ion exchange softeners in this state is significant, it does not adversely impact conventional wastewater treatment processes. Reduction of TDS might be valuable in the future if the intended reuse application of waste water requires a higher quality of water. * |
