Transforming Industrial and Sewage Effluent into Water for Reuse Using Chemicals
Chemistry is critical in addressing the challenges associated with industrial and sewage effluent treatment.
There are two different types of effluent water treatment: Industrial and sewage effluent treatment. Differing significantly from each other in terms of their content, they each have their own set of quality-related challenges. Chemistry is critical in finding the solution to address these challenges.
Industrial effluent treatment
Effluent can be treated for reuse across almost all industries, including, for example, food and beverage, metal finishing, plastic manufacturing, and textile.
With any effluent treatment, one of the main challenges is that there is a multitude of influents, resulting in the effluent that requires treatment being of a significantly complex nature. Influents in a metal finishing factory, for instance, can stem from acid wash, alkaline wash and zinc bath processes. These result in fluctuating levels of pH and metal concentrations.
Chemistry for treating industrial effluent
Generally, the chemical processes that are implemented to treat industrial effluent are pH adjustment, coagulation, flocculation, oxidation and disinfection.
pH correction: Sodium hydroxide dosing ensures that pH is increased. The dosing is fitted with pH control, due to the fluctuating quality of the effluent, thus enabling the system to monitor the quality and dose accordingly. In comparison, acids are dosed to reduce pH levels.
Coagulation: Suspended pollutants, such as solids and organics, that are either too small to be filtered or remain stubbornly stable in solution require the addition of a coagulant to allow them to either settle out of solution or clump together in order to be filtered.
Oxidation: Oxidation is any chemical reaction that involves the moving of electrons. Specifically, it means the side that gives away electrons. Sodium hypochlorite is typically introduced to assist in the oxidation of dissolved organics, met, and microbial content before moving on to the next stages of treatment.
Disinfection: A dosing pump adds the chemicals needed to disinfect the water, such as sodium hypochlorite or chlorine dioxide, on a consistent basis. This keeps biological growth at bay through to point of use, ensuring that the water remains clear and bacteria-free.
Once treated, industrial effluent can be used for industrial processes or cleaning purposes.
Sewage effluent treatment
Sewage – effluent stemming from residential and commercial properties – is waste water and excrement conveyed in sewers. This type of effluent is organically based by nature.
A major challenge in terms of treating sewage effluent is the solids that get disposed via sewers, from diapers to clothing, even before biological processes.
Chemistry for treating sewage effluent
Treating sewage using chemicals eliminates harmful pathogens; expels hazardous chemicals, detergents and toxins; reduces odour and improves water colour; and extracts valuable substances and clean water from the sewage.
Biological treatments are usually employed to treat sewage: Reducing the solids in the effluent to sludge that can be treated. Some common methods include anaerobic treatment, aerobic treatment, coagulation, and disinfection.
Anaerobic treatment: Anaerobic bacteria transforms ammonia in the wastewater into gaseous nitrogen that can easily escape into the atmosphere.
Aerobic treatment: Introduction of air into the system promotes growth of aerobic bacteria. These bacteria further reduce COD and promotes nitrification.
Nitrification: Nitrifying bacteria transforms soil ammonia into nitrates (NO3−).
Coagulation: Coagulants are used to allow the sludge to settle out of solution or clump together.
Disinfection: The addition of chemistry such as calcite hypochlorite, chlorine dioxide or sodium hypochlorite ensures that effluent water stored has a residual of disinfectant present, preventing microbial growth.
Treated sewage water can typically be used for irrigation or other non-potable purposes such as toilet flushing.
If you are ever in need of a tailored effluent treatment solution, WPS is available to provide expert assistance anywhere in South Africa. Contact us anytime to discuss your water-related challenges.