Water pollution is a serious problem for lakes, oceans, and rivers. What some may not realize is that it also occurs every day in our own homes. The difference is that we are not actively or carelessly attempting to pollute the water we use. Rather, it becomes polluted while we use it by substances such as food waste, human waste, and cleaning products like shampoo and dish soap. While wastewater is not safe for human use, it can be made safe again through water pollution treatments. There are different treatments used to purify water, but none are considered ‘superior’ to others. In fact, combining different methods results in the most effective water pollution treatments.
Physical Water Treatment
As the name would suggest, physical water pollution treatments do not use any chemicals. Common physical treatment methods include sedimentation, aeration, and filtration.
During sedimentation, the insoluble and heavy particles are suspended from the water that is being treated. This results in those particles settling at the bottom, making it possible to separate pure water.
Aeration is the process of providing oxygen to the wastewater by circulating air through it. It removes dissolved gases, oxidizes dissolved metals, and removes volatile organic chemicals (VOCs). Aeration can be done in one of two ways, either by introducing water to air or air to water.
Filtration involves filtering out the impurities. There are multiple types of filtering, each involving different equipment depending on what is being removed (bacteria, solid matter, etc.). The types of filtering are greensand filtration, microfiltration, nanofiltration, multimedia filtration, and ultrafiltration.
Reverse osmosis is another method that is mostly used in industrial water treatment.
Biological Water Treatment
Biological water treatment relies on bacteria and other microorganisms, such as nematodes, to break down waste and other impurities in the water. There are two main methods of biological treatment, aerobic and anaerobic.
Aerobic treatment uses oxygen to allow the bacteria to decompose organic matter in the water. It becomes converted into carbon dioxide, which is then used as a source of energy by the plants. Composting and activated sludge are two types of aerobic treatments.
Anaerobic, by contrast, works in an oxygen-free environment. The best-known anaerobic treatment is anaerobic digestion. The primary biogas produced in this waste-to-energy method is methane.
Chemical Water Treatment
Different chemicals are added to the water to target other contaminants. Chlorine is added as a disinfectant, and manganese can be added to the aeration process to target dissolved iron. Neutralization, another common chemical treatment, returns the water to its natural pH balance of 7 by adding either an acid or a base, depending on how high or low its current pH balance is.
Sludge treatment separates the solid waste, in sludge form, from the water. There are two types of sludge, primary and secondary. Primary sludge is generated from other treatments such as sedimentation, and secondary sludge is activated biomass from biological treatments. It is a multiple-step process that usually begins with ‘thickening’, in which the primary sludge is thickened to about 8-10% solids and the secondary to about 4%. The next step is dewatering, a term referring to any process that reduces the water content, such as centrifugation.