Application Corner: A problem of high sewage flow

Previous columns described the sewage collection systems for two adjacent sewage districts and how the costs associated with operating the sewage treatment plant were allocated and billed.

As a side note to previous discussion, the billing agreement terms provided ample incentive for the first sewage district to maintain a tight sewage system with low inflow and infiltration (I&I).

On one occasion, the first district noticed an unusually high sewage flow through one of the four flowmeters during the wee hours of the night. Underground sewage pipes were temporarily blocked off in an attempt to locate the source of what seemed to be excess sewage.

After a few nights, testing pinpointed the source to be coming from one sewage pipe that served a handful of residential houses. Internal examination of the houses revealed that so much groundwater was leaking into the basement of one of the houses that its sump pump was pumping the groundwater to its sewage pipe almost continuously to prevent the house from flooding.

One of the workers mentioned that it seemed like a river was flowing through the basement directly to the sewage system. This resulted in an additional sewage expense of approximately $20 per day (approximately $7,000 per year) plus additional surcharge billing on wet weather days. The homeowner was given an offer that could not be refused: fix the problem within a few days or pay the difference in the sewage bill.

Read more next issue about the high cost of surcharges.

David W. Spitzer is a principal at Spitzer and Boyes, LLC, which offers engineering, focused market research, writing/editing white papers, strategic marketing consulting, distribution consulting, seminars and expert witness services for manufacturing and automation companies. Spitzer has written more than 400 technical articles and 10 books about flow measurement, instrumentation and process control. He can be reached at 845-623-1830 or via spitzerandboyes.com.