What Is Water Treatment?
Water treatment involves a series of physical and chemical processes to purify water. These include coagulation/flocculation and sedimentation-separating out heavy particles, filtering the water through sand, chlorine or charcoal and disinfection to kill bacteria.
Most communities rely on natural bodies of water like lakes, rivers and oceans for their drinking water supplies. This is why water treatment is essential.
Pretreatment
Water treatment is necessary to ensure safe, clean drinking water. It reduces the concentration of contaminants that can cause diseases such as cholera, typhoid and dysentery.
Pretreatment processes can be used to remove a wide range of contaminants, including turbidity, hardness, dissolved oxygen and pH. This can help extend the lifespan of filtration membranes and enable them to meet regulatory requirements.
Secondary treatment involves aerating wastewater to release dissolved gases such as hydrogen sulfide and to replenish oxygen. It also uses bacteria to consume organic matter and nutrients in the wastewater. The resulting sludge is then digested anaerobically or aerobically before it is returned to the ecological system. This process can prevent nutrient enrichment in rivers and lakes which can lead to eutrophication, killing fish and other aquatic life.
Coagulation
Small particulates are suspended in natural and wastewater water. They carry different charges, but repulsion prevents them from combining into larger particles that settle down. Coagulation is a chemical process that helps these particulates to combine and become heavier, thus making them easier to settle.
This is done by using chemical coagulants, such as aluminum sulfate (alum), ferric sulfate or sodium aluminate. Other types of coagulants include sago, which is made from a plant; chitin, which is derived from the exoskeleton of crustaceans; and polyaluminium chloride.
Temperature has a significant effect on the solubility of coagulants water treatment and their reaction rate with suspended particles. Generally, higher temperatures result in faster reaction rates and higher removal efficiencies. The coagulation process also depends on the dosage of chemicals used and the type of coagulant.
Sedimentation
The physical water treatment process of sedimentation is used to remove large solids from water. This step, sometimes referred to as settling, is an essential part of most municipal water treatment processes.
Coagulants are added to the water to neutralize the charges on particles and cause them to bind together into larger groups called flocs. These flocs are easier to separate from the water because they are heavier.
Flocs are then moved to a sedimentation basin, also known as a clarifier or a settling basin. These tanks are designed with low water velocities, which allow the flocs to settle easily.
For the best results, a sedimentation tank should be sized based on TSS, solids characteristics, and settling velocity. Laboratory tests and jar testing help to gather this information.
Filtration
Many water treatment processes require large amounts of energy. The energy demand depends on the quality of the source water and whether pumping is involved. Water treatment processes that avoid the need for pumping use less energy.
The filtrate is the liquid that passes through the filter medium and accumulated solids. The accumulated solids are known as the filter cake.
The filtered water can then be disinfected using ozone gas. This process is very effective at water treatment supplier killing harmful bacteria and microorganisms in the water. The disinfected water can then be returned to the environment.
Disinfection
The goal of disinfection is to kill pathogenic bacteria, viruses and other microorganisms. Water treatment plants use chlorine and other chemical disinfectants (including oxidizing agents, such as sodium hypochlorite), ozone or ultraviolet light to accomplish this.
The most common and oldest method of disinfecting water is chlorination. It works by continuously disppensing chlorine chemicals into the water. This oxidizing agent kills most bacteria and some viruses.
The number of coliform bacteria in the treated water can serve as a measure of fecal contamination. It is important to note that microbial pollution in raw water cannot be completely eliminated. However, the EPA sets standards for acceptable levels of microbial pollutants that are permitted in drinking water. These are generally expressed in terms of colony forming units per milliliter of water.
Stabilization
The quality of water is vital to all living things. Access to clean, safe drinking water is a human right but billions of people struggle to get it. Water treatment systems are designed to guarantee people’s access to water and ensure it is safe for consumption.
Whether you have your own private well or buy your water from a municipal system, it’s important to know how the water is treated. Water treatment protocols must be constantly followed to avoid contamination and maintain a healthy and clean water supply. To do so, a good recordkeeping system must be used to track the quality of the water and the results of treatment processes. This helps to identify issues or trends that require attention. Then, corrective actions can be taken.
Ozone
Ozone is a powerful oxidizing agent that can quickly disinfect water and destroy fungi, bacteria, viruses and cysts. It is more effective than chlorine, but unlike chemical chlorine it does not leave any chemical chlorine residue in the water.
Ozonation eliminates pathogenic viruses and bacteria and parasites that cause various diseases if ingested. It can also lower the turbidity of the water by eliminating organic matter like silt and clay. Ozonation can also oxidize iron, manganese and sulfur to form insoluble metal oxides and elemental sulfur, which can then be removed via post-filtration. In addition, ozone can eliminate the bad odors and tastes caused by certain impurities like hydrogen sulfide. This can be accomplished by bubbling the ozone gas into the water. It only lasts for about 20 minutes in the water before it begins to decay.
