Application of mixture of coagulants in greywater treatment

University of Debrecen

Doctoral School of Chemistry

Bodnár Ildikó

chemistry

Greywater (GW) is wastewater generated from kitchen, bathroom, and laundry, excluding wastewater from toilets. GW may include significant quantities of lipids, surfactants, fabric softeners, oils, chlorides, and sulphates among other pollutants, as well as be contaminated with disease-causing organisms. GW reuse is a major approach in sustainable and integral water management in multiple countries where the population suffers acute water shortage and relieves strain on freshwater resources, minimizes pollution that is discharged into water bodies. GW may be utilized for non-potable activities such as domestic cleaning, flushing toilets, washing vehicles, agricultural irrigation. And there is the potential to increase the total availability of water resources if the use of GW was to be adopted globally. Locally treated GW lessens the load on the distribution system, lowers the time and expense required for construction, and, whenever feasible, reduces the carbon footprint associated with it. Such locally treated GW provides significant way to expand local water resources. In line with the sustainable development goals of the WHO and UNICEF, it is a major step towards mitigating the decline in clean water supply in water stress areas as well as the aspirations for the future.
Treatment systems are categorized based on the methods used for segregation and separation, including physio-chemical and biological treatments. The water is disinfected, and any remaining impurities undergo coagulation during the tertiary treatment, which is mainly chemical process. Modern methods have been developed recently to increase treatment effectiveness. Physio-chemical treatment technologies aim to remove impurities from GW by combining physical and chemical processes. Appling coagulation and flocculation in GW treatment is a crucial step in the process of removing impurities and contaminants, making it suitable for reuse. While traditional coagulants such as alum or ferric chloride have been commonly used, advancements in technology have led to the development of new and innovative coagulant treatment methods. These technologies offer improved efficiency, reduced environmental impact, and enhanced overall performance in treating GW. Flocculation then promotes the formation of larger particles, making it easier to separate them from the water.

GW is typically thought to be safer than other wastewater, but if utilized improperly, it can have a significant negative impact on health. The risks associated with recycling of GW depend on the application, such as agricultural irrigation, whose primary hazards mostly rely on whether it is reused on a short-term or long-term basis.
This doctoral topic investigates the application of different type and ratio of coagulants in GW treatment. Synthetic and real greywater will be prepared/collected and tested in the laboratory with addition of different type of coagulants (e.g. ferric chloride, lime, polyelectrolytes and combination of them as a new approach) will be studied. Useful parameters such as pH, zeta potential, turbidity, electrical conductivity, organic content and microbial characteristics of the samples will be measured. Applying so-called JAR tester the optimal flocculation conditions also will be delimited. Suitable post-treatment methods (filtration, adsorption, sedimentation) will be also studied.
The treated GW quality parameters will be compared the actual legal requirements to produce good quality reclaimed water for non-potable household or locally reuse options.

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University of Debrecen, Faculty of Engineering, Department of Environmental Engineering

2026-01-15

english