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City of Paso Robles
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Address
Wastewater Division Treatment Plant
3200 Sulphur Springs Road
Paso Robles, CA 93446
Phone
(805) 237-3865
(805) 237-3886 FAX
Hours
Mon-Fri 7am to 3:30pm
E-mail
wastewater@prcity.com
Wastewater

WATER SOFTENER ISSUES

There is more to water softeners than just soft water. Water softeners reduce the “hardness” of the water, which can have several benefits for consumers: smaller amounts of soap and detergents (non-synthetic) are necessary for laundry and cleaning processes; reduced staining, spotting, scaling; bathing and showering feelings; increased fabric life; and energy saving in water heating due to less scaling.

How does a water softener work?
A typical water softener softens water by ion exchange, which involves the exchange of the hardness minerals, chiefly calcium and magnesium, for sodium or potassium minerals.

The exchange takes place by passing water containing hardness minerals over ion exchange resins in a tank. As the calcium and magnesium contact the resin in their travel through the resin tank, they displace sodium or potassium ions. The displaced sodium or potassium ions pass downward through the resin “bed” and out the softener drain; thus, the softener delivers “soft” water.

The Problem
The discharge of salt brines from the regeneration of water softeners into the wastewater collection system has a negative impact on recycled water and wastewater effluent. Higher salinity increases the treatment costs and reduces the potential for reuse of wastewater for non-potable irrigation and industrial purposes. It can also impair a wastewater treatment agency’s ability to comply with discharge standards for total dissolved solids (TDS) which is a measure of the total concentration of dissolved minerals in water, including concentrations such as sodium, calcium, magnesium, potassium, and anions such as chloride, sulfate, and many others.

A typical wastewater treatment facility removes very little of these mineral concentrations from the waste stream and are passed on to the environment.

Sodium really has no redeeming value in the environment outside of saltwater or brackish water ecosystems. It has been declared as the biggest contaminate affecting water supplies in California, the nation and the world. Water with salinity levels above 1,000 mg/l is of questionable use for irrigation and industrial customers. As salinity increases, laundry detergents work less efficiently, plumbing fixtures and home appliances wear out faster and industry incurs higher treatment costs for boilers, cooling towers and manufacturing processes, and farmers experience reduced crop yields.

Results of Noncompliance
Every wastewater treatment facility in the State must meet strict limits issued by the State and Federal agencies on the amount of TDS and mineral concentrations before reclaimed wastewater can be introduced back into the environment. If a wastewater treatment facility is found to be in violation of it discharge limits by these agencies significant fines may result. Presently the City of Paso Robles wastewater treatment facility is experiencing some difficulty in meeting its TDS, sodium, sulfate and chloride discharge limits. One of many contributing factors to this problem is salt brine from water softening units.

Possible Solutions
Finding practical, cost effective solutions to this problem has been difficult. So if you decide to use a water softener you should determine if a softener is necessary. Water with a measured hardness of less than 50mg/l is considered soft. Generally water 50 to 150 mg/l is suitable for use in most homes and it is not necessary to use a softener.

If you find that a softener is necessary then a possible solution is to switch to potassium chloride from sodium chloride in your softener. This substitution will indeed solve the sodium problem. The downside of potassium chloride it will add to any chloride problem and costs more than sodium chloride.

Another possible solution, which may not solve but can greatly reduce the problem is to use less salt. Most softener owners use at least twice as much salt to soften water as is necessary. By adjusting your softener to use the proper amount of salt per regeneration required to soften your water may greatly reduce the amount of sodium or chloride being used and subsequently discharged to the sewer. If salt usage is reduced operating costs for chemical replacement can be found.

Lastly, it has been found that many softeners are set to recharge or backwash too frequently. Again by adjusting the backwash cycle to the appropriate time period between each backwash can significantly reduce the amount of sodium or chloride being discharged into the sewer system. Instead of a daily or every other day recharge cycle, a five-day cycle may be used to achieve the proper softening level.

Conclusion
The solution to the salinity problem in water supplies is going to a very long, difficult and costly process. But every one can help by using the least amount of sodium possible or finding more environmentally friendly ways to soften water.


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