Dilution is the solution to pollution
Land treatment of industrial waste water can save energy. Mechanical aeration for treatment demands large quantities of electrical power. In land treatment, this is replaced by passive aeration. The energy cost reduction can be well in excess of the payments needed to purchase the land. A disadvantage of land application of waste waste is that it can contribute to ground water salinity.
Crops and soil treatment do little to remove mineral salinity from applied waters. How much salinity in ground water is too much? Salinity doesn't threaten health as much as it taints taste. This creates a dilemma. Environmental regulators are challenged to defend enforcement limits based on aesthetics with the same vigor as criteria based on human health. They are particularly challenged when the industries contributing to groundwater salinity are valued employers contributing to rural economies. But defend water quality standards they must.
Salt load in land applied waste water is considered by many to be the single most important challenge facing the industries which use land application to treat waste water. Particularly sensitive to this issue are briners, cheese processors and some electronics manufacturers. Among waste water spray field management advisers the consensus is that saline waste water spray field operations should avoid sites where the discharge can't be diluted by substantial rainfall and/or groundwater flux. In short, dilution is the only practical solution when it comes to salts in waste water. If the operation is located in an area that does not enjoy the benefits of natural dilution, the brine portion of the waste water stream can be segregated and transported to an area that does. Not an easy task but not unprecedented. A municipal waste water treatment plant discharging to a substantial body of water is a logical choice for receiving the brine.
These comments are prompted by a news article today in the Sacramento Bee (free registration required): Hilmar faces more pollution rules. Cheese factory agrees to give water quality board more authority.
[follow-up comment from Chris Bowman, Sac-Bee: The brine collected from the reverse osmosis filters is hauled to an East Bay MUD treatment plant.]
