|
|
|
|
|
|
|
Corrosion is most severe at lift stations where turbulence occurs to release hydrogen sulphide in the wastewater. Lift station equipment and appurtenances must be carefully selected to be corrosion resistant and drop inlets used to reduce turbulence. |
|
|
|
|
|
|
|
|
Typically, utility or special purpose districts are formed to administer, operate, and maintain SDGS systems located outside municipal boundaries. These districts vary in structure from state to state, but they usually have most of the powers of municipal government, except for bonding authority. |
|
|
|
|
|
|
|
|
The districts usually assume responsibility for all SDGS components downstream from the inlet to the interceptor tank. As the interceptor tank is critical to the performance of the system, it is important that the utility has the responsibility for its maintenance. In most projects, the utility owns the interceptor tank and service lateral. A general easement, or easement by exhibit, has worked well to gain access to the components located on private property. |
|
|
|
|
|
|
|
|
Septage pumping, treatment and disposal are usually provided by private pumpers under contract to the district. Pumping frequencies vary depending on the type of connection. Food service establishments may need pumping as often as every 6 months while residential homes may not need pumping for 710 years. |
|
|
|
|
|
|
|
|
Mains flushing usually is recommended on an annual basis, but experience in Australia and the USA has shown that routine flushing is not necessary. Successful hydraulic flushing can be accomplished by discharging clear water into cleanouts and removing the accumulated solids from downstream manholes or lift station wet wells. Flushing two to three pipe volumes has been shown to be effective in removing all slimes growths from the pipe wall (Otis, 1986). However, flushing has seldom, if ever, been performed in SDGS systems in the USA and Australia. |
|
|
|
|
|
|
|
|
A review of construction costs from 12 SDGS projects showed that 2050 per cent savings were achieved over conventional |
|
|
|
|
|