STEP Systems and the EnviroFilter: Elegant Solutions for Communal Developments
The pre-assembled package EnviroFilter™ Wastewater Treatment System is a major advancement in onsite wastewater treatment technology. It incorporates a highly efficient engineered textile media, an elegant design for the attached growth process utilized, and a patented construction that enables the system to be assembled in a single compact tank. This delivered system reduces construction time, eliminates installation errors and provides fast start-up with full treatment performance in days when other systems take weeks.
In community systems and subdivisions, the elegance of the EnviroFilter™ is enhanced when combined with a modern Septic Tank Effluent Pumping (STEP) system as a means of centralized collection of the wastewater from each household. A well-engineered STEP system is a cost-effective, safe, leak-free means of moving the effluent from the primary treatment tanks associated with each household to the EnviroFilter™ secondary treatment system. The STEP system provides initial treatment, solids storage, solids digestion, and effluent collection in a single package.
Key to the STEP system is providing primary treatment at each household and collecting the effluent through small diameter pressure sewers. This is done with on-lot primary treatment (septic) tanks at each household unit, or by using a central primary tank for multiple household units in clusters or condominium developments. Separating the solids and the fats/oils/grease in the primary tanks means only the gray water effluent is traveling through the sewer system, allowing smaller lines, eliminating manholes and groundwater infiltration, and reducing maintenance expenses. It also enables more design flexibility of the land as individual disposal fields are eliminated, so living units can be clustered leaving more desirable green space while allowing more lots.
The primary treatment tanks in the EnviroFilter STEP system are constructed of fiberglass and have been water-tested for leaks. These tanks are structurally strong and designed for an unlimited life.
Each primary tank in the STEP system has a low horsepower, high head pump in a vault within the tank. The gray water from the tank is pumped into small diameter plastic pipes which collect the flows from all of the tanks and delivers it to the centralized EnviroFilter™ packaged treatment system. Properly designed pumps, laterals and force mains constitute a pressurized system that does not require gravity for fluid transport, so it can traverse varied topographies and longer distances easily. Consisting of small diameter pipes buried directly in the ground, this piping network can be installed quickly and simply with smaller equipment than traditional gravity sewer systems, significantly lowering costs and community disruption.
Advanced treatment is performed in the EnviroFilter™ pre-assembled treatment unit, or series of units for larger flows. EnviroFilter™ units can be provided in individual capacities of up to 12,000 gallons/day, and combined to achieve the desired system capacity.
Each project is subject to varying permit requirements that are usually dependent on the selected effluent disposal method and local conditions. The typical EnviroFilter™ produces effluent with BOD and TSS levels below 5 mg/L and Ammonia below 1 mg/L. With easily added supplemental treatment, Total Nitrogen can be brought below 15 mg/L and Fecal Coliform can be brought below 200 cfu/100ml. At these tertiary treatment levels, many regulatory agencies will allow disposal field horizontal and vertical separation reductions, setback reductions, and set-aside elimination. These benefits provide additional site design options for additional green space and/or additional lots.
The treated effluent may also be dispersed by beneficial reuse in surface or subsurface irrigation systems reducing the demand for potable water. At these treatment levels, the effluent can also be surface discharged to streams (local standards apply).
Cost and Environmental Benefits
- No deep excavations that are expensive and disrupt the community, can be installed by directional boring for minimal surface disruption
- Eliminates the need for granular backfill and manholes required for gravity sewers
- Eliminates lift stations that are expensive, odorous and require continual maintenance
- Eliminates line cleaning as the small diameter sewers are self-cleaning and flushed daily during high flows
- No sewage solids in pipes
- No storm water infiltration that can overload the treatment system
- No leaky pipes, manholes and gravity connections that can let groundwater inflow and overload the system
- No requirement for full-time maintenance personnel
- Smaller overall investment than traditional gravity system
- New units can be connected to the system as they are built, reducing upfront capital costs and enabling on-lot equipment to be part of the unit cost
- EnviroFilter™ treatment system can be expanded on a phased basis as the development grows, so no unused infrastructure has been paid for
While the STEP system has inherent benefits with many wastewater treatment systems, the cost-effectiveness of the EnviroFilter System compared with others stands out in applications requiring treatment of 600 to 60,000 gallons/day with advanced treatment levels.