Options for Commercial Wastewater Treatment When Regulators Will Not Approve Conventional Septic Systems (and municipal sewer is not available)
With the advent of increasingly stringent environmental regulations coupled with difficult site conditions including poor soils, high groundwater and other issues, it is becoming more difficult to obtain permits for conventional septic systems on commercial and public projects. However, several options exist for advanced (secondary) wastewater treatment that can enable commercial and public projects to obtain regulatory approvals by treating wastewater to a high quality prior to discharge.
Advanced wastewater treatment systems utilize septic tanks to provide primary treatment. After solids have settled in the septic tanks, the resulting liquid (effluent) is further treated by a filtering device. This filtering device usually consists of an attached growth filter in which organic matter is removed from the effluent by microorganisms that grow on the filter media. Various types of filter media can be used including sand, gravel, peat, textile fabric, plastic, etc. Following advanced treatment, the effluent is discharged to groundwater by subsurface disposal fields (leach fields) or spray irrigation. Alternatively, it can be discharged to surface water via a stream or other waterway. In some cases, the effluent can be re-used to irrigate landscape vegetation or re-routed into buildings for use in toilets.
While it is possible to design an advanced treatment filter from locally available materials, several companies such as Orenco, Quanics, Bord Na Mona, HydroLogex, and others manufacture pre-packaged filter units that ship in self-contained basins that can be assembled on site. Additionally, these pre-packaged systems can be constructed in phases so that treatment capacity can be implemented in increments that meet the phase plan of the project. The phasibility aspect can substantially reduce initial capital expenditures compared to package plants where the entire plant must be constructed at one time.
Advanced treatment filters are an excellent way to solve difficult wastewater challenges while being inexpensive to operate compared to mechanical package plants. This is because they have lower energy requirements, they are simple to operate and they require little maintenance. Additionally, advanced treatment filters are relatively inexpensive compared to mechanical treatment plant alternatives.
Although advanced treatment filters are fairly simple in concept, an engineered design that integrates the site conditions with the selected treatment system design parameters will be required by regulators. Additionally, the various options for manufacturers, media types, package components, etc. should be carefully considered according to the site specific variables of the project to ensure the treatment system will work and meet owner and regulatory requirements.
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