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

by Mike McGinness, EcoShield Environmental Systems, Inc.
February, 2005

Large Month-to-Month changes in BOD, TSS

Q. We have septic tanks and sand filters with chlorination and dechorinations systems, we lab test samples once a month. What causes the BOD,s and TSS and Ammonia Nitrogen levels to go from next to none one month, and then be over our permit range the next month.

BOD for December--4.5 mg/L; January--12.8 mg/L
TSS for December--8.0 mg/L; January--43.0 mg/L
Amm Nitrogen for Dec.--1.2mg/L; January--17.5 mg/L

What has caused this to happen, and what can we do to keep our levels about the same each month.

A. Without more details, doing an onsite inspection, having an opportunity to ask questions of various maintenance personnel ..., etc., all I can do is take some educated guesses.

Seasonal temperature changes can be part of your problem. Also using the wrong kind and quantity of cleaning / sanitizing chemicals for sanitary maintenance can be upsetting the process. Check with your chemical sanitary maintenance supplier and make sure you are using the best available cleaning and sanitizing agents for use with septic systems.

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