What Does Industrial Wastewater Contain?
Industrial wastewater contains a variety of contaminants that require removal before discharge. These can include high concentrations of metals, BOD / COD, and TSS.
Different treatment processes can be utilised to meet the requirements set out by regulatory bodies and ensure that the wastewater is safe for disposal or reuse. What type of treatment is required depends on the physical, chemical and biological characteristics of the wastewater and what the end goal is.
High Amounts of Nitrogen
Nitrogen is an essential nutrient in many plants and animals. During the nitrogen cycle, bacteria and other single-celled prokaryotes convert atmospheric nitrogen to biologically usable forms, such as ammonia (NH3) and urea (NH4+).
In wastewater treatment facilities, nitrogen can enter the treatment system in several ways. It may be released directly into the atmosphere in chemical reactions, or it can come into the water from fertilizers or storm-water runoff that contains nitrate.
Wastewater that is collected for treatment typically contains a high concentration of total nitrogen, which is the sum of organic and ammonium nitrogen. The most common form of nitrogen in wastewater is ammonia nitrogen, and it accounts for about 70%-82% of the total nitrogen concentration in wastewater. The remaining nitrogen is in the form of nitrite and nitrate.
Industrial wastewater contains a wide range of chemical components. Some are easy to remove with physical processes (such as sedimentation or filtration) while others need chemical treatment first because they’re difficult for bacteria to degrade.
For example, soluble heavy metals such as aluminum, copper, iron, hexavalent chromium, nickel, and lead can be difficult for bacteria to break down. These toxic contaminants often require chemical treatment before biological wastewater treatment can begin.
Acidic or basic chemicals can be added to the wastewater solution to adjust pH to increase hydroxide ions that bond with the metals and precipitate out of the water solution. Greater acidity also helps to kill bacteria by breaking down organic compounds at a cellular level.
Industrial effluent contains pollutants that are harmful to aquatic life and the environment. Some are a result of the disposal of chemicals, while others may have been emitted directly into waterways.
Some substances in wastewater can cause serious harm to human health when they reach high concentrations (such as cadmium, thallium, zinc, lead, and mercury). Other compounds may be toxic only at lower levels, such as organic materials.
Many pollutants are also hazardous to soil, plants, and animals. For example, persistent organic pollutants (POPs) — such as aldrin, chlordane, dieldrin, endrin, dioxin, and hexachlorobenzene — can accumulate in the fatty tissues of animals and can cause cancer and other diseases.
Toxic substances can be removed from wastewater through a variety of methods. Some can be disposed of as trash, while others may be reused or recycled as a valuable coproduct. Using a holistic approach to wastewater treatment can help ensure that the waste is not causing additional environmental and health problems.
Industrial wastewater contains heavy metals such as lead, zinc, chromium, nickel, and manganese. These metals are dissolved in the wastewater solution and infiltrate into water ecosystems, causing several environmental and health impacts.
A variety of remediation processes are available to reduce the effects of these pollutants on living organisms and the environment. Some of these include chemical, microbial, and phytoremediation.
Adsorption and ion exchange are two common methods used for the removal of heavy metals. The removal efficiency of these processes depends on the initial concentration of the metal ions, pH values, chemicals added to the wastewater, and other factors.
Coagulation-flocculation is another method used to remove heavy metals from wastewater. This technique has a dual process consisting of sedimentation and coagulation, followed by flotation to separate the metals. The coagulants are typically alkaline reagents, such as iron salts and alumina.