Treatment of wastewater involves procedural activities starting with preliminary, primary and secondary treatments.
Preliminary water treatment involves removal of debris and coarse biodegradable material. In this process, wastewater flows from sewers connected businesses premises and homes into sewer plants. The incoming wastewater (influent) then flows through screens. These screens have several upright bars 3 inches apart which eliminate large particles. The resulting garbage from this process is transported to landfills (Tchobanoglous et.al, 2003). The final step of the preliminary water treatment involves lifting the wastewater from the screens to the plants surface.
After preliminary treatment of wastewater, the wastewater enters primary settling tanks. These tanks are also known as sedimentation tanks. Water flows slowly in the tanks to ensure that lighter particles remain afloat while heavier trash sinks. Thereafter, the lighter particles are skimmed from the resulting solution. The primary sludge consisting of settled solids is then pumped through cyclone degritters (Tchobanoglous et.al, 2003). Large particles are separated through a centrifugal force generated by the cyclone degritters. The primary sludge that has been degritted is transported to sludge-handling facilities. The resulting wastewater is then channeled to secondary treatment system.
Secondary treatment is also known as the activated sludge process due to the fact that seed and air sludge are added to the wastewater. In secondary treatment of wastewater, air is pumped into large aeration tanks. The aeration tanks mix the sludge and wastewater. This process enhances the development of oxygen-using bacteria that consume the remaining materials that are considered water pollutants. The resulting wastewater then flows through bubbling tanks for aeration that takes about 3 to 6 hours (Grady & Grady, 2011). The returned sludge has many microorganisms that maintain the balance between air and bacteria (Hernández, 2010). This process enhances the removal of water pollutants.
The major differences between the three processes include the fact that they remove different water pollutants. For example, the preliminary water treatment removes large particles while primary water treatment removes finer particles. Finally, secondary water treatment removes minute water pollutants including microorganisms.
Wastewater in the City of Los Angeles is collected and treated through different facilities that ensure that the city not only provides water to its residents but also supplies water to other parts of United States. This is in light of the fact that Los Angeles is the largest supplier of treated water in the United States. Wastewater in the city of Los Angeles is conveyed through Hyperion Treatment Conveyance System (HTCS). The conveyance system is operated and managed by the Los Angeles Department of Public Works (LADPW). LADPW supplies water to 640,000 customers making one of the most successful departments in the city (Ladwp.com, 2017). LADPW obtains water from several sources including, the Metropolitan Water District of Southern California (MWD) (53%), groundwater (11%), Los Angeles Aqueduct (35 %) and recycled water (1%).
There is a sewer service in Lomita that also offers water treatment and sewerage services for the city of Los Angeles. This sewerage service is provided by the Los Angeles County Sanitation District No 5. The sewer service is responsible for the treatment of approximately 290 million gallons of wastewater every day. The sewer treats water for human consumption as well as for disposal. Treated water is disposed to Pacific Ocean.
Metropolitan Water District of Southern California (MWD) is another facility that is responsible for the treatment of water not only in the city of Los Angeles but also in most parts within South California. MWD has its headquarters in the city of Los Angeles. MWD is a collaborative of 26 smaller water districts. The facility is the largest supplier of treated water in most metropolitan areas of the United States including Los Angeles (Metropolitan Water District of Southern California, 2017).
Grady, C. P. L., & Grady, C. P. L. (2011). Biological wastewater treatment. Boca Raton: Taylor & Francis.
Hernández, L. (2010). Removal of micropollutants from grey water – Combining biological and physical/chemical processes. PhD thesis, Wageningen University
Ladwp.com (2017). Los Angeles Department of Water and Power. Retrieved 29 October 2017, from https://www.ladwp.com
Metropolitan Water District of Southern California. (2017). Mwdh2o.com. Retrieved 29 October 2017, from http://www.mwdh2o.com/