Ask the Expert Question-and-Answer Archive
by Mike McGinness, EcoShield Environmental Systems, Inc.
I saw a reply of yours on the WEF technical discussions forum on the use of peracetic acid for a bakery pretreatment system. I am doing some research for alternative disinfectants for a WWTF in our state. This is a municipally operated plant that treats commercial, biopharmaceutical and brewery wastes. The municipal plant experiences numerous fecal coliform violations. The theory is that the pharmaceutical company discharges large volumes of HEPES buffer solution. HEPES buffer is non-biodegradable and contains organic nitrogen. It is believed that the chlorine is combining with the organic nitrogen to form organochloramines, a useless disinfectant. We are investigating other chemical disinfectants for the municpal plant to use that wont't combine with the organic nitrogen component. Peracetic acid is one possibility, but haven't found any full scale applications in this country. I have read that it is widely used in Europe, especially Italy. Do you have much experience with this chemical?
It rapidly breaks down into acetic acid and H2O2 if the pH gets above a certain point, probably above 6 to 7 pH. It also breaks down in the presence of trace metals like copper. The H2O2 breaks down at alkaline pHs and in the presence of trace metals too. While it works as a surface disinfect at an acid pH, when used as surface spray in a bakery, I would have concerns about cost effectiveness, and 1/2 life. It would also add to the COD and BODI would suggest looking at ozone, possibly as a pretreatment step at the biopharmaceutical point of discharge, or at the municipal discharge. Ozone might be able to detoxify the HEPES as well as make it biodegradable, and is an excellent disinfectant.
Sounds like an interesting problem! Let me know if I can be of further assistance.