For about 30 years, environmentalists, fishers, and farmers have waged a war over salt- and selenium-laden drainage from agricultural lands. The contaminants are remants of ancient in-land seas and have caused environmental disasters decades ago.
Steps in recent years have dramatically reduced the amount of “bad water” that has flowed from farms into rivers and marshlands. But despite the 80 and 90 percent reductions that have already been realized, tainted water continues to flow into the San Joaquin River, damaging the fishing environment downriver. Now, a $30 million treatment plant being funded by the U.S. Bureau of Reclamation will test a potential problem stemming from the 97,000 affect agricultural acreage.
Already, farmers use run-off reclamation systems to capture irrigation water from beneath crops. That salt-heavy water is then used to irrigate salt-tolerant crops such as pistachios. But once used again, the water contains almost as much salt as seawater. Once completed treatment facility will use reverse osmosis and aerobic digesters to further clean the discharge.
After reaching the treatment facility, the water would pass through a reverse osmosis membrane to remove salt and selenium. After initial treatment, half of the water would have characteristics suitable for irrigation. The other half would proceed into digesters where bacteria would further breakdown contaminants, resulting in water as clean as the water released from the first round of reverse osmosis.
However, a ”sludge” of contaminants of salt, selenium, and other metals will be produced and must be treated as hazardous waste.
The system, if successful in offering further protections to marshlands and rivers, could be the model for a larger facility to treat the entire affected area.
Information in this article was drawn from the Fresno Bee.