The effectiveness of In-Pipe Technology (IPT) patented sewer collection system engineered bioaugmentation on i) influent wastewater loads to wastewater treatment plant (WWTP), ii) WWTP performance, and iii) effluent quality, was a demonstrated at a domestic sequencing batch reactor (SBR) WWTP (Sewer District #20) in Suffolk County, Long Island, New York in collaboration with the Suffolk County Department of Public Works (SCDPW) and the New York State Energy Research Development Authority (NYSERDA). The influent loads, e.g., biochemical oxygen demand (BOD5), total suspended solids (TSS), and total Kjeldahl nitrogen (TKN) to the WWTP decreased by approximately 13%, 13%, and 5%, respectively, With-IPT bioaugmentation treatment compared to Pre-IPT treatment. The WWTP operating costs associated with aeration energy and sludge disposal was reduced due to the reduction of the oxygen requirement (15-20%) and sludge production (-10%). The effluent water quality improved with a reduction of BOD5 (-17%), TSS (-30%) and TKN (-13%) loads With-IPT bioaugmentation treatment compared to Pre-IPT treatment. In conclusion, the continuous introduction of beneficial and more robust microbiology in the sewer collection system as prescribed by IPT enhanced the existing WWTP performance without capital expansion and with reduced operating costs.
Historically, the sewer collection system is thought of only as the conduit for transporting wastewater from various sources to the WWTP, but it contains similar treatment capabilities as a biological reactor designed for treating wastewater. Huisman [1J showed that a 23.1 km gravity collection system contains as much as 9,500 m' (1.7x10 m'/MGD) wetted biofilm surface area, which is equivalent to a 105 m stone filled trickling filter reactor. The biochemical transformations occurring in bulk water and biofilm phases in the sewer are initiated by microorganisms (mostly by heterotrophic bacteria). The biochemical processes have the potential to change the influent wastewater quality (e.g., enhancing the readily biodegradable chemical oxygen demand (rbCOD) fraction of the total COD) and, in some cases, to reduce the influent load (e.g., biological oxygen demand (BOD5), total suspended solids (TSS), and total Kjeldahl nitrogen (TKN)) entering the WWTP . Hydrolysis of hydrolysable COD and the utilization of rbCOD are the most important processes in the sewer collection system. However, utilization of the rbCOD in the sewer collection system depends on the availability of electron acceptors (e.g., oxygen, nitrate, and sulfate). Heterotrophic bacteria consume wastewater rbCOD as electron donors, respire using oxygen, nitrate, and sulfate as an electron acceptor under aerobic, anoxic, and anaerobic conditions, respectively, and convert rbCOD to carbon dioxide, nitrate to nitrogen gas, sulfate to sulfide, and biomass . Nitrate respiration is limited in sewer collection systems since ammonia is the dominant form of nitrogen in raw wastewater and autotrophic ammonia nitrification to nitrate or nitrite most likely will not take place due to short resident time. Sulfate respiration is undesirable since the respiration by-product odorous hydrogen sulfide is toxic to human health and the sulfide oxidation product sulfuric acid is corrosive to the sewer infrastructure. Heterotrophic bacteria can also consume wastewater rbCOD and grow through fermentation processes under anaerobic conditions. Any increase in rbCOD through hydrolysis of the hydrolysable COD in sewer collection systems depends on the enzyme production capability of the indigenous microbial population.