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QUALITY AND TREATMENT OF GRAYWATERS IN FAMILY HOUSE

Petr Hluštı́k, Veronika Singrova, Jaroslav Raclavský

Abstract

The concept of greywater reuse has been gaining importance recently. These systems are also becoming a must in Europe, where there has not been such a pressure exercised on greywater (shower and bath water) reuse to date. The situation is dynamically changing, some countries in southern Europe start facing a lack of drinking water and new water resources must be searched for. Recycling some of the water is also encouraged by the fact that these systems are cheaper that sea water treatment. The main reason for greywater recycling is reduced drinking water consumption, its minimum pollution, simple treatment and a requirement for building assessment certifications in terms of the environmental impacts. Greywater from households accounts for up to 50% of water in the total consumption, the volume of produced greywater in selected countries fluctuates between 57 and 75 l/(PE·day). In administrative and public buildings, the volume of water is defined by the equipment of building (administrative buildings 80-90 l/(PE·day), three-star hotels 150 l/(PE·day), five-star hotels up to 1,000 l/(PE·day)). In terms of chemical composition, the ratio between COD and BOD is usually 3.5-4:1 which points to a higher share of hardly degradable organic matter (in traditional municipal water, the COD/BOD ratio is usually 2:1). This unfavourable ratio mainly applies to shower water containing soap and shampoo. The pH of greywater (the pH of municipal water is usually 7?8) and, in particular, the pH of washing water, is basic ( pH=9?10), while water from classic kitchens is rather acid. Greywater temperature coming from bath tubs, showers and washing machines fluctuates between 18 and 38 °C, as warm water is used for hygienic purposes. It is necessary that the greywater systems should be designed to ensure water production suitable for the relevant purpose without any risk to human health. Frequent water sample testing is not needed; nevertheless, water quality monitoring should be carried out during maintenance work in order to check the performance of the greywater systems. If the system operation is not satisfactory, the causes should be established along with the potential problems with water consumption from the system. The article deals with the technology of gray water purification in family houses. It recommends the use of calculated values for the design of the treatment unit, ie the average values of the material and hydraulic load of gray waters.

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DOI resolver: doi.org/10.5593/sgem2020/4.1/s17.021

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