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BACKGROUND: In order to provide high quality potable water for our communities, we should first consider our options for water sources. An analysis of our available raw water sources usually leads us in a direction that is readily apparent!

GROUNDWATER: If the community has a producing groundwater aquifer that can support one or more additional wells, then the community constructs additional wells, usually spreading them out in the system so that they do not interfere with one another. This allows the community to grow, adding more homes and businesses. Schools and maybe a small hospital may also be connected to the water distribution system. Reservoirs, and emergency generators for the wells and 'ground-level reservoir' pumps are added when the community decides that it needs these added protections. Groundwater sources are usually of an acceptable water quality that does not require additional treatment prior to being utilized in the community. Some groundwaters may have to be treated to remove dissolved gases, and in some cases elements like iron and manganese. The water may be fluoridated and/or chlorinated using elemental chlorine, chlorine dioxide, or sodium hypochlorite,  prior to being distributed into the community. The chlorine that is added is usually of a very small amount, approximately 1 mg/L or in lay-person's terms, about one pound of chlorine for every million pounds of water. This chlorine is used to protect the water quality by controlling any biological re-growth in the distribution system.

If the groundwater sources are not available, or we are unable to continue using groundwater sources, we usually turn to surface water sources such as streams, rivers, and lakes. This water source is more difficult to use as it most always requires treatment, and the changing seasons change the quality of the raw water which requires a trained operator to monitor and adjust the treatment processes to address the changing raw water source.

SURFACE WATER TREATMENT: The treatment processes that are selected for our community are based on a number of factors. Some of these factors are: the cost and the amount of land available, the topography of the community, the constituents in the raw water we will be treating, the concentrations of the silts, sands, inorganic and organic constituents and suspended solids in the raw water, and the financial resources of the community. Additional items concerning the community's water are: water rights, raw water source control, future water quality regulations, water conservation plans, and water demand and water production estimates.

The quality of the surface raw water source usually dictates the types of treatment processes used to treat it.  For the purposes of simplification, we will discuss two usual types of potable water treatment facilities: Direct Filtration and Conventional Filtration.  When the surface water source is low in turbidity and constituents (for comparison a high mountain lake), Direct Filtration is used. When the raw water source is high in turbidity (for example a river) we usually see Conventional Filtration-type facilities designed and constructed.

DIRECT FILTRATION: The raw water is usually pumped into the treatment facility where it will then usually flow continuously by gravity through the treatment facility. The raw water enters the Preliminary Treatment process where it may be screened, and any silt and sand is removed. From there it flows to the coagulation and flocculation process where we usually add an inorganic salt or an organic polymer to coagulate the fine particles in the water and flocculate them into larger particles. The water then flows into the filtration process. The filters may be conventional sand filters, multimedia filters, Diatomaceous Earth (DE) Filters or similar, depending on the type of materials desired to be filtered out, etc. Once the water has been filtered it then passes to the disinfection process for disinfection where it may be disinfected by use of chlorinated water water using elemental chlorine, or chlorine from chlorine dioxide, or sodium hypochlorite;  or by using UV disinfection systems. The water may also be fluoridated prior to being distributed into the community.

CONVENTIONAL FILTRATION: The raw water quality is usually higher in turbidity when compared to direct filtration systems. As such it usually enters the Preliminary Treatment process where it may be screened, and allowed to pass through a Pre-sedimentation Basin or a specifically designed sand basin where any silt and sand is removed. From there the raw water flows to the coagulation and flocculation process where we usually add an inorganic salt or an organic polymer to coagulate the fine particles in the water and flocculate them into larger particles. This water is then directed into clarifiers (also called sedimentation basins) where these coagulated and flocculated particles settle to the bottom of the tank. Conventional Filtration plants rely heavily on these clarifiers to reduce the amount of turbidity that will be applied to the filters. It is far more cost affective having the sedimentation process remove this heavy load than the filtration process. The clarified water then flows into the filtration process. The filters may be conventional sand filters, multimedia filters, Diatomaceous Earth (DE) Filters or similar, depending on the type of materials desired to be filtered out, etc. Once the water has been filtered it then passes to the disinfection process for disinfection where it may be disinfected by use of chlorinated water water using elemental chlorine, or chlorine from chlorine dioxide, or sodium hypochlorite; by using UV disinfection systems or ozonation disinfection systems. The water may also be fluoridated prior to being distributed into the community.