Epsilon Archive for Student Projects

Abstract

The growth of the global population, the increasing need of water for agriculture and the increasing urbanization put great pressure on the existing resources of freshwater and the finding of news sources of freshwater become necessary. An alternative source of water can be to reuse wastewater.

Greywater is all wastewater from a household, with the exception of toilet water, which is called blackwater. Water from dishwashing, from kitchen sinks and from laundry machines constitute greywater and it account for 80% of the household wastewater.

Greywater can be reused in areas that do not require portable water such as irrigation and toilet flushing.

The reuse of greywater reduces the pressure on freshwater resources and thereby preserves the environment and decrease the cost of water. Greywater in this scenario is a resource of water rather than wastewater.

Unfortunately, greywater by its origins contains chemicals, bacteria and viruses. The reuse of raw greywater without a pretreatment can have negative impacts on the soil, can pollute the groundwater, the surfacewater or/and contribute to the transmission of diseases.

The high cost and the insufficiency of centralized wastewater treatment plants mainly in low income countries justify the choice of the onsite filtration system with local and inexpensive filter materials.

In this study, bark, bio-char and activated charcoal were used as filter media in column filters.

Some physical and chemical parameters of greywater that can have a negative environment impact were measured before and after filtration. The concentration of two bacteria and two viruses were estimated before and after filtration. The filters were run for ten weeks.

Differences between different bacteria, between different viruses and also between bacteria and viruses contribute to them having different properties that effect the way in which they interact with filter material. The filtration efficiency thus depends on both the microorganism and the filter material. Activated charcoal filter was found to be better in reducing some of the chemical parameters. The bark filters have an acidifying effect on the filtrated greywater and was less effective in reducing the viruses analyzed. The bio-char was found to be better at reducing the bacteria studied.

This study had contributed to the finding of methods to improve the quality of greywater for reuse. The study confirmed the possibility to improve the quality of greywater by filtration and showed that degree of the reduction depends of the filter material used and the characteristics of the microorganisms.