2.2. Waste Water system
Public Sewer System
Public sewer systems are generally installed in cities and municipalities where the local government has decided the population is large enough to need a centralized system for sewage disposal. Septic systems are used by residents living outside of the city limits or in very small towns where a public sewer system is not financially feasible A public sewer system directs waste to a centralized water treatment facility where organic solids and sludge are removed, the water is treated and then discharged to a local water body. Many homes are able to connect to the system via gravity feed but sometimes lift pumps are employed to get the waste to the treatment plant. Being connected to a public sewer system can be very convenient for the homeowner who does not have to pay the installation cost of a septic system. Many issues, including taking the extra measures to break down solids and remove oils, are also undertaken by the public system and are not a concern to the homeowner
Private Sewer System
Today’s private sewage treatment system contains three components: the house where the waste is generated, the septic tank where the partial treatment takes place, and the subserface seepage system, which provides for final treatment. Wastewater generated within the house comes from a variety of sources including showers, toilets, sinks, garbage disposals, dishwashers, bathtubs, jacuzzi/whirlpools, floor drains and washing machines. Most of the solid waste comes from the kitchen sink, garbage disposal and toilets. Other facilities produce quantities of wastewater with only limited amounts of soil and detergents.
A wastewater collection system comprised of "separate" and "combined" sewers. Separate systems are comprised of two independent piping systems: one system for "sanitary" sewage ( sewage from homes and businesses) and one system for storm water. * Combained Sewer System
Systems that carry a mixture of both domestic sewage and storm sewage are called combined sewers. Combined sewers typically consist of large-diameter pipes or tunnels, because of the large volumes of storm water that must be carried during wet-weather periods. They are very common in older cities but are no longer designed and built as part of new sewerage facilities. Because wastewater treatment plants cannot handle large volumes of storm water, sewage must bypass the treatment plants during wet weather and be discharged directly into the receiving water. Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and then discharged to a water body. During periods of heavy rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, or other water bodies
* Separate Sewer System
A separate sewer system consists of two different sewer pipes running one on top of the other. In most instances, the sanitary pipe is below the storm pipe. The sanitary sewer pipe transports sanitary sewage collected from the laterals (plumbing connections) of homes, businesses, and industry to treatment plants. The storm water sewer pipe carries water collected from street inlets, building downspouts, and other storm sewer lines to a nearby receiving stream and is discharged through a Storm water Outfall.
* Surface run-off, greywater and backwater can be managed separately (no contamination of surface run-off by sewage) * Limited or no risk of sewage overflow
* Convenience (minimal intervention by users)
* Low health risk
* No nuisance from smells,...
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