Greywater Characteristics and Reuse in Tower Gardens in Peri-Urban Areas - Experiences of Kawaala, Kampala, Uganda

ABSTRACT

This study was undertaken to create an understanding of greywater characteristics and to demonstrate a low cost reuse option involving application of small tower gardens for Greywater treatment and reuse in a peri-urban settlement, Kawaala in Kampala city, Uganda. To realise this, field surveys, greywater and soil sampling and analysis and, tower garden installation at selected households were undertaken. The common sources of greywater in Kawaala were found to be kitchen, bathroom and laundry with the majority of the households (72%) pouring laundry water in open drains and spaces adjacent to their homes. The greywater generated in the area exhibited high BOD5 (71-873 mgL-1) and COD (140-4886 mgL-1) and E.Coli (<0-13900 cfu per 100 mL) values necessitating treatment prior to disposal in the environment. The greywater had low average BOD5/COD ratio (<0.5) meaning that it is not easily treatable by biological means. Greywater application to the tower gardens, had limited impact on the soil potassium, organic matter and nitrogen content but increased the phosphorus content. The vegetables grown in the greywater towers thrived but were attacked by pests necessitating pest control. The households with the tower gardens appreciated the simplicity of the technology. To create demand for it requires sensitization and social marketing within the community. There is need to determine the hydraulic load of a tower garden to guide the number and size for a particular quantity of generated greywater for optimum performance. Also further monitoring is needed to ascertain the vegetable yield per soil volume, impact on crop growth and people's livelihoods.