What is wastewater, and why treat it?
Wastewater, often called effluent, is used water which contains substances such as human waste, food scraps, oils, soaps, and chemicals. In homes this includes water from sinks, showers, baths, toilets, washing machines, and dishwashers. Wastewater is full of contaminants like bacteria, chemicals, and other toxins, which have a negative impact on the environment and our health. This can include harm to fish and wildlife populations, oxygen depletion, and contamination of drinking water. Most of the water used by homes, businesses, and factories must therefore be treated before it can be safely released back into the environment.
The major aim of wastewater treatment is to reduce contaminants to acceptable levels and remove as much of the suspended solids as possible, to make the water safe for discharge back into the environment. We are going to discuss the three main types of wastewater treatment below:
Physical water treatment
Physical water treatment typically consists of filtration techniques that involve the use of screening, sedimentation and skimming to remove any solids or harmful impurities from the water. Firstly, wastewater is passed through various screens and strainers designed to separate solid pollutants such as hair, wet wipes, and food waste, from the water. You can install specialist tanks, that are designed to separate these solids and prevent them for entering or blocking your drainage system. For instance, grease separator tanks are an effective and hygienic method of separating fat and grease from wastewater flow in restaurants or hotels.
Physical water treatment often acts as a preliminary step to reduce the load on wastewater treatment plants, and to ensure the efficiency of subsequent fine purification systems that could be damaged if large solids or major impurities were still present in the water. Wastewater is often then passed through sedimentation processes which use gravitational forces to help separate any remaining solids or impurities from the water. Gravity causes solid material to sink to the bottom of the settling tank and form a sludge; this can then be easily removed from the liquid. Membrane filtration technology can also be used to remove smaller dissolved or undissolved particles from the wastewater. This includes microorganisms, bacteria, proteins, and yeast.
Chemical water treatment
Chemical treatment involves using chemical reactions to improve the water quality. The most commonly used chemical process is chlorination. Chlorine, a strong oxidizing chemical, is used to kill any remaining parasites, bacteria, and viruses and to protect the water from germs when it is piped to homes and businesses. Ozone is another strong oxidizing agent that can be used to disinfect wastewater. Neutralisation is another chemical process which is commonly used to treat wastewater. This process involves adding acid or alkali as required, to adjust the pH levels of the water back to neutrality.
Biological water treatment
Biological wastewater treatment relies on the action of naturally-occuring bacteria and other microorganisms to break down organic waste and clean water. The goal of biological wastewater treatment is to create a system in which the results of decomposition are easily collected for proper disposal. This is often a secondary treatment process used to remove any particles remaining after primary treatment, such as the physical processes discussed above. Biological treatment is usually divided into two broad categories: anaerobic and aerobic treatment. “Aerobic” describes a process where oxygen is present, while “anaerobic” refers to a biological process with no oxygen.
Aerobic wastewater treatment - This includes treatments such as activated sludge process, oxidation ditches, trickling filters, and aerobic digestion. In this process forced air from an air blower or compressor is mixed with the wastewater. The aerobic bacteria feeds on the waste in the water to convert organic matter into carbon dioxide. This is the most efficient biological waste treatment and it can remove up to 98% of organic contaminants.Anaerobic wastewater treatment - This process uses a gastight cover to create an oxygen-free environment. The anaerobic bacteria breaks down the organic matter present in the wastewater and transforms it into biogas, which can then be removed.
