Solids in water refer to suspended or dissolved materials in drinking, surface and brackish waters, as well as domestic and industrial wastewaters. Solids may affect water and wastewater quality in a number of ways. Waters with high dissolved solids are generally of lower quality and may cause adverse physiological responses in the consumer, so a maximum of 500 mg of solids per liter is desirable for drinking water.

Raw water intakes draw water from various specified levels in rivers, lakes, or reservoirs behind dams. In order to protect the pumps and remove large objects from the water before it enters the pumping station, strainers are usually installed in the intake structure. Aeration is a process unit that removes gases and volatile organic compounds that cause taste and odor problems in the water supply system.

Secondary disinfection provides an essential residual that prevents the regrowth of microorganisms in the distribution network. Chlorine, chloramines, and chlorine dioxide are commonly used as secondary disinfectants. However, chloramine is the most commonly used secondary disinfectant. Chloramine is not virucidal and is only slightly effective in killing Giardia cysts.

Aeration has little effect on taste and odor removal. Most of the compounds that cause taste and odor have high solubility in water. Therefore, except in a few cases, aeration is usually less effective in removing taste and odor than other methods such as chemical oxidation or adsorption.

When water passes through various stages of purification, it must be disinfected to the extent necessary, depending on its intended use. For example, drinking water, after purification and removal of suspended and dissolved substances, must be free from any microbial contamination and not pose any health and safety risk to the consumer. The destruction or inactivation of microscopic organisms and pathogenic microorganisms is known as water disinfection.

Softening processes are used to reduce water hardness. Using chemicals, water hardness undergoes chemical reactions and precipitates. As a result, water hardness is reduced. Water hardness is due to the presence of carbonates, sulfates, chlorides, and nitrates of the metals calcium, magnesium, iron, and aluminum.

Water treatment wastes are materials that are removed in various treatment processes and contain large amounts of water. These wastes include turbidity and color-producing materials, organic and inorganic solids, algae, bacteria, viruses, and precipitated chemicals. These materials are by-products of chemical coagulation, iron and manganese precipitation, filter washing, hardening, resin regeneration, and microfilters.

All water sources contain a wide range of organic and inorganic impurities. Water purification is the process of removing undesirable components from water and then disposing of them in the easiest and safest way. To achieve this goal, various purification processes are used that utilize different physical and chemical phenomena to remove or reduce undesirable components from water. The selection of purification processes is one of the keys to the successful operation of any water treatment plant.

Because each water source is unique in terms of chemical composition, it is often necessary to conduct treatability studies to obtain design and operating parameters for treatment processes. Such studies are particularly important where a new treatment plant is proposed.

The main objective of a water treatment plant is to produce water that meets drinking water quality standards at a reasonable cost to the consumer. In a water treatment plant, various processes are used to produce water of desired quality. These processes are generally divided into two general categories: operational units and process units.

The steel industry uses large amounts of water. However, very little is consumed, as most of the water is reused or returned to the source. Water is used not only in cooling operations, but also in other processes such as scale removal and dust cleaning.