The collection system is often viewed simply as a means to transport wastewater to the treatment facility. The many hours that wastewater remains in the collection system helps promote the growth of “wild” bacteria including filamentous bacteria, Sulfate Reducing Bacteria (SRB), which lead to the production of hydrogen sulfide, and odor causing bacteria. As a matter of fact, the indigenous biological growth within the collection system can be harmful to infrastructure and is generally considered detrimental to objectives of wastewater treatment plants.
One company has developed a technology and service that use biological processes to turn the collection system into an active part of the treatment process. The system also can help reduce O&M costs for sewer maintenance and cleaning.
The system offered by In-Pipe Technology® Co. involves the introduction of high concentrations of select, facultative, symbiotic, spore-forming, naturally occurring, non-pathogenic bacteria at strategic locations in the outer reaches of a collection system.
In-Pipe’s microbiological treatment program is engineered for each specific sewer system, based on such factors as organic loads, distribution, collection system layout, and treatment objectives, among others. Battery-powered dosing units consist of a panel slightly larger than a shoe box containing a solenoid pulse pump operated by a small circuit board. The dosing panel holds a replaceable reservoir and can provide time controlled treatment for as long as 90 days.
Over time, the added bacteria convert the biofilm on the surface area of the infrastructure into a controlled, beneficial biological population. By out-competing the non-beneficial bacteria for nutrients, the microbes grow and populate the sewer pipes and lift station wet wells.
Using the collection system as a pre-treatment step improves WWTP efficiency in a number of ways. The bacteria work with or without oxygen inside the sewer system, converting organic materials and nutrients into carbon dioxide and nitrogen gas. Each pound of organic material and nitrogen removed in the sewer during transit, without energy input, is a pound that does not require treatment in the WWTP. This conversion involves two distinct operations, namely the conversion of TSS into a soluble format that bacteria can metabolize and the actual metabolism of the soluble material into carbon dioxide and nitrogen gas.
Case Study
The municipal wastewater treatment plant in Crown Point, IN, selected the In-Pipe system to reduce the amount of waste sludge for disposal, increase organic capacity and control odors at the plant.
Crown Point, in northwest Indiana approximately 45 miles from Chicago, spent nearly $200,000 on sludge-related expenses ranging from polymer costs to hauling and disposal fees. Population growth there also has increased sludge production and staff were faced with the prospect of expanding the existing sludge storage building. In addition, management hoped increasing the organic capacity of the facility would increase the MCRT (Mean Cell Residence Time) to push back the need for a new anaerobic digester expected to cost $1 million.