Basic Functions of the Wastewater (WW) Treatment Plant
Wastewater treatment plants are essential for purifying water released from homes, businesses, and industries. The plants ensure that the effluent is safe for release into wetlands or water sources such as streams and rivers. The WW treatment plants remove harmful pollutants and speed up the natural process of water purification. They comply with current environmental laws and regulations by ensuring that water released for domestic or industrial use is free from solids, microorganisms, and dangerous elements. The processes of wastewater treatment also safeguard public health.
Most Common WW Pollutants
Dissolved Oxygen is the amount of free, non-compound oxygen that is absorbed directly in water. The level of dissolved oxygen affects the life of aquatic life and fish. However, high levels are suitable for the growth of microbial, which cause disease and affect health. Pathogens, which include bacteria, viruses, and protozoa pose the risk of disease to animals and humans. The most hazardous are viruses that are easily carried in water and cause acute and chronic infections when one consumes untreated water. Another category of pollutants is heavy metals such from processing industries and oil refineries. Heavy metals such as lead, zinc, and mercury are a serious threat to flora, fauna, and humans, especially when in high concentrations. Their toxicity stems from the ability to bind proteins in the body and change the structure of molecules, which results in health complications. Additionally, hydrocarbons are found in wastewater effluents. The environmental impact of hydrocarbons is, and their presence in water has been found to cause damage to body organs and systems.
Basic Wastewater Treatment Processes
Wastewater discharge is treated by local water authorities to remove pollutants that are harmful to the environment or which could damage the sewer system. The process involves several stages, starting with primary treatment. The wastewater undergoes removal of trash using bar screens and settling whereby contaminants are allowed to settle in a settling tank. The contaminants are then removed from the bottom of the tank in a step that constitutes clarification to make the water clear. The wastewater is then disinfected through chlorination to remove all dangerous microorganisms. In the secondary treatment, the dissolved particles are then removed from the water through a biological process that injects microorganisms, mostly bacteria, to feed and convert them. The process takes a long time but is effective in purifying the water. The next step uses techniques that are either physical or chemicals. This stage can substitute the use of microorganisms since the addition of chemicals or physical techniques (such as filtration) change the structure of particles forming a sludge which is easily removed. The step uses acidic and caustic chemicals to adjust the water pH to the desired level. The water is then let out to an open channel.
Different Options for Use or Disposal of Wastewater Residuals and Bio-Solids
The residual collected after the secondary treatment is separated into the organic and inorganic matter. The former undergoes anaerobic digestion to produce methane gas that is used to produce power used in the treatment plant. Alternatively, the sludge is stabilized and used in farmlands as fertilizer and soil conditioner in environmentally acceptable ways. The inorganic residuals are disposed of in landfills that are designated for that purpose. Alum-rice and iron-rich bio-solids are used to bind excess phosphorus in the soil thus are useful in land application.