An Assessment Of Ph, Toxic And Essential Plant Elements In Greywater From Selected Households In Kenyatta University, Kenya

Kenya is experiencing acute water shortage resulting to water rationing, conflict among water users, increased water prices among others. Therefore, there is need for water conservation. One of the water conservation methods available today is greywater reuse. Greywater is domestic wastewater generated from kitchens, bathrooms, and laundry activities. According to World Health Organization (WHO) each household in capital cities of most countries produces an average greywater flow of 356 litres per day. Kenyatta University generates a lot of greywater from its premises including staff quarters, messes, hostels and offices, but all goes to waste because in Kenya, greywater is not adequately utilized probably due to inadequate information about its quality and safety. Greywater contains nutrients especially nitrogen, phosphorus and potassium and its re-use in irrigation would improve food production. However, greywater may also contain toxic elements to plants such as lead and cadmium hence need for its treatment. Greywater treatment methods such as biological, physical and chemical exist, all intended to improve the quality of greywater for reuse in irrigation. Some of these methods are costly to install and unavailable in developing countries like Kenya. Therefore, there is need to study the properties of greywater generated and where possible its treatment done before its application in irrigation using relatively cheap treatment technologies. Greywater sampling was carried out in Kenyatta University staff quarters. The present study determined the levels of plant nutrients (K, Ca, Mg, Fe, Zn, NO3--N and P), toxic metals (Cd and Pb), and pH in the raw greywater and after treatment through sand, activated carbon and ordinary (raw) wood charcoal filtration. The data obtained was analysed using ANOVA. The results in ranges of pH, nutrients and toxic metals were as follows; pH-5.88 to 8.98, K-1.59 to 28.40 mg/L, Ca-6.46 to 51.30 mg/L, Mg-0.92 to 13.24 mg/L, Zn-0.02 to 0.99 mg/L, Fe-0.12 to 4.04 mg/L, P-0.33 to 15.57 mg/L, NO3--N-0.11 to 10.39 mg/L, and Pb-0.01 to 0.19 mg/L. Cadmium was not detected in all the samples. The results of the study indicate that the levels of Pb, Zn, Fe and P in raw greywater were statistically lower from those in activated carbon and ordinary wood charcoal filtrates while those of K, Ca and Mg in raw greywater and the filtrates were not significantly different at 95% confidence level. The NO3--N levels were found to increase significantly with sand filtration, probably due to oxidation of nitrites to nitrate during the greywater filtration process. From this study it can be concluded that both raw and filtered greywater can be used for irrigation since the levels of all the parameters were within the ranges recommended/allowed by WHO for crop irrigation and Kenya Bureau of Standard (KEBS) for drinking water. Therefore greywater can have dual usage as source of plant nutrient and for irrigation, thus preserving freshwater and increasing food production hence enhancing the achievement of Kenya’s Vision 2030.