Ask the Expert Question-and-Answer Archive (Wastewater Treatment)

by Mike McGinness, EcoShield Environmental Systems, Inc.
August, 2002

Treating Wastewater from Soak Cleaner and Degreasing Operations

Q. Our Company does metal finishing (chrome and nickel in rims and bumpers). Metal degreasers in the form of detergents and soak cleaners are used only previous to the plating operation. Could you please suggest a treatment for wastewater coming out of this part of the operation?

A. If there is a totally seperate rinse for the cleaner solution, and if you are not dragging any dissolved metals into that rinse from the plating tanks, then a pH adjustment step and pH control (around 7.2) followed by an aerobic (feeding air) bioconversion step to convert oil and grease into filterable bio mass should do the trick. This assumes that the rinse water is already too high in Oil and Grease or BOD to meet the permit discharge limits. Many cleaning step rinses can meet POTW discharge with out pretreatment if they are not also used for rinsing plating solution off the parts.

It is usually the cleaner itself that is hard to treat or dispose. After filtration you should be able to easily meet city discharge permit limits for a local POTW. The next question is do you have a POTW that you can discharge waste to? If not then you may want to consider other options. Using a 2 stage rinse is one option. The first rinse is then used as make up water for the cleaning bath evaporation losses.

EcoShield manufactures a simple low cost package that is designed for the Aerobic bioconversion option (IPBR-500) discussed above. You may also want to consider EcoShields proprietary ACRS technology that converts oil and grease into reusable cleaning surfactants. It can also be used to extend the life of rinse water and remove oil & grease from rinse water. Both are discussed in detail on the EcoSheld web site (http://www.ecoshieldenv.com/bio.htm and http://www.ecoshieldenv.com/prod01.htm).