INNOVATIVE SANITARY COLLECTION SYSTEM – THE SMALL BORE SEWER™

Sewage is the largest waste (by volume) produced by communities, and wastewater treatment is a heavy cost burden to all municipalities. Large, quick groundwater flows infiltrate into sewer piping during storm events causing design engineers to oversize systems for these infrequent occurrences, as treatment plant operators bypass sewage in order to save plant equipment. Affordable and cost-effective sewage collection systems, while maintaining or improving environmental protection, are often sought out by municipal engineers; however, traditional gravity sewers allow excessive amounts of infiltration and inflow (I/I) to enter into the sewer network, overwhelming the treatment plant with surges of diluted sewage. The uptake of innovative technologies has been limited by consultants but innovative technologies and superior materials exist to create inexpensive, sealed sewer collection systems. The evolution of the small diameter variable gradient (SDVG) sanitary collection system into the watertight Small Bore Sewer™ system has proven that removal of sewage solids at source and removal of inflow/infiltration can eliminate bypass occurrences and reduce the size of the downstream plant.In 1989, a pilot project was implemented in a northern Ontario community and its success propelled further development of the innovative collection system into a larger scale project in Wardsville, Ontario in 2000. After seven years of data collection, this 300 equivalent residential unit project uses only half of the designed capacity at the treatment plant, demonstrating that the sealed effluent collection system delivers small, steady flows to the downstream treatment plant in a consistent manner without the influence of seasonal storm events.The three main advantages of the system are that the technology creates lower overall effluent flow volumes, reduces effluent chemical demand and reduces total sludge handling. The technology can also be designed based on the Ontario Ministry of the Environment (MOE) approvals to lower design flows and lower peaking factors. This has a direct impact on other component design, resulting in smaller pumping stations, force-mains and treatment facilities. The system can offer significant cost savings in sewage treatment plants as well as lower long-term operation and maintenance costs.Strategies to adapt these projects into American and Canadian scenarios can be successful if all stakeholders (residents, community members, elected officials and staff of the Department/Ministry of the Environment) recognize the impact that unnecessary inflow/infiltration and solids conveyance have on a sewer system network and waste-water treatment plant. In new rural development, Small Bore Sewer™ systems allow increased density of development when compared to development with conventional septic systems. Communal systems allow more efficient use of the land base, and at the same time, communal systems provide much higher protection to the environment with suitable treatment systems, they have been demonstrated to cost less than properly designed and installed septic systems, and to cost less than conventional solutions, while keeping clean groundwater in the ground and not diluting sewage at the treatment plant.