CH2M HILL, a global leader in full service engineering, construction and operations, was tasked to find a way to treat the concentrate stream from a water treatment plant located in Sherman, Texas USA. The City wanted to be able to treat this wastewater in order to reduce sewer and wastewater plant loadings, and to recover a portion of the wastewater as high quality water than could be used to increase plant finished water capacity.
The plant had an 11MGD capacity, treating surface water from Lake Texoma. Electrodialysis Reversal (EDR) was used to demineralize a portion of the filter effluent from the conventional water treatment plant. The EDR process produced a constant waste stream of approximately 1MGD that was being discharged to the City’s sewer system.
The poor quality of the concentrate stream, which contained a high content of sparingly soluble salts in excess of their theoretical solubility, made it impractical to use conventional desalting methods. Based on previous work published by Zeta Corporation on membrane fouling mitigation for RO systems, CH2M HILL evaluated the Zeta Rod in conjunction with an innovative RO system, developed by GrahamTek, as a means to prevent or reduce fouling of RO membranes to treat the waste stream.
Pilot tests were run using a Zeta Rod System in front of a GrahamTek RO system with reject recirculating capability. During the tests there were some membrane problems related to the high free chlorine content in the water, however, CH2M HILL concluded that the Zeta Rod system had shown beneficial effects.
“The Zeta Rod improved operability of the conventional RO treatment (relative to no pretreatment) although the mechanism responsible for the observed reduction in membrane fouling is not well understood. Feed pressures and WTC were more stable during Zeta Rod use at 50% recovery than without its use at 15% recovery.”