CH2M HILL evaluates Zeta Rod & GrahamTek RO systems to reclaim EDR wastewater


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.”

Click here to link to the CH2M HILL Feasibility Study for EDR Wastewater and Recovery