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

by Mike McGinness, EcoShield Environmental Systems, Inc.
January, 2003

Lime or Sodium Hydroxide?

Q. How are the majority of metal finishers treating their process wastewater? (i.e. Are they using lime or caustic and why might they prefer one over the other?) Any and all information that you can provide regarding wastewater treatment in the metal finishing industry would be very helpful to me. Thanks!

A. I know some have used lime in the past and I have used it for acid neutralization (especially HF), but the 50% liquid sodium hydroxide is much easier to dispense and control than the lime. It also produces less sludge (typically). Also some are using magnesium hydroxide (also a solid or powder feed) instead of lime since it produces several times less sludge than lime, and it it has an upper pH limit of 10, which makes it very safe to use and hard to over treat.

 

 


The information contained in this site is provided for your review and convenience. It is not intended to provide legal advice with respect to any federal, state, or local regulation.
You should consult with legal counsel and appropriate authorities before interpreting any regulations or undertaking any specific course of action.

Please note that many of the regulatory discussions on STERC refer to federal regulations. In many cases, states or local governments have promulgated relevant rules and standards
that are different and/or more stringent than the federal regulations. Therefore, to assure full compliance, you should investigate and comply with all applicable federal, state and local regulations.