African Status quo and requirements of treatment and reuse technology

A research report of Sino-Africa wastewater treatment cooperation was released by Beijing Municipal Research Institute of Environmental Protection and Tongji University, to explore the possible wasterwater treatment technology transfer mechanism between China and African countries.

Accroding to this report, several primary problems impeding the development of sewage treatment of Africa are listed below:

(1) Low rate of sewage collection and treatment

Due to lack of sanitary facilities, the rate of sewage collection and treatment is extremely low and a large volume of raw sewage is discharged directly into water body. Dakar, the capital of Senegal, owns a municipal sewage system only serving 25% households in 2003 and the treatment capacity is less than 10,000m3/d.

(2) Major application of stabilization pond system

Limited by shortage of funds and energy, aerobic (mechanically aerated) biological process is seldom adopted in Africa, while stabilization pond treatment system plays a major role. Effluent usually goes into rivers after anaerobic, facultative and aerobic pond. Currently stabilization pond process has several concerning issues:

a) Most raw industrial wastewater goes into treatment plants directly, which leads to a significant organic overload. The COD of influent frequently exceeds 2,000 mg/L.

b) Serious sludge sedimentation at bottom of stabilization ponds could often be observed because lack of proper maintenance such as regular desludging operation. That decreases actual handling capacity of stabilization pond treatment system (sometimes it is only about half the designed value). Since funds are limited, regular dredging or desludging could not be carried out and many stabilization ponds are not working properly in reality.

c) In aerobic ponds, screen cleaner is necessary for effective removal of solids. Installation of a screen cleaner requires a reliable power supply, but because of frequent power outages in many African regions, the cleaning system is not able to be operated continuously. This significantly impacts the performance of subsequent aerobic pond treatment systems. Even though several sewage plants have their own in-house electricity generator, it is not sustainable because it increases the cost of running the treatment plant.

d) Sewage disinfection is insufficient due to lack of funds, thereby having a negative impact on the receiving water environment.

e) Impeded by weak economy, it has a negative influence on the water environment

(3) Strong demand for sewage irrigation

The lack of water creates a demand for sewage reuse, especially for agricultural irrigation. There are two primary hurdles preventing sewage irrigation from being used for agricultural purposes. The first one is cost. Construction of basic facilities for sewage irrigation is difficult because of limited funds. The second is lack of available technology and management capability. Even in the few countries which may have the economic capacity to reuse their sewage water for agriculture, their lack of technical knowledge and skills as well as limited administrative and logistic capabilities make it a colossal effort to build and operate such facilities. In addition the import channel for technology and equipment from outside has not facilitated the importation of technology or equipment due to the administrative ambiguity in the distribution liability. Consequently related works has not been carried out smoothly.

(4) Immaturity of sewage advanced treatment

Some African countries are planning to upgrade all sewage treatment plants, adding artificial wetlands for advanced treatment at the end of aerobic pond system. However, the process from planning to actual implementation is often hindered by lack of technology and funds.

(5) Inappropriate operation management and lack of experience on maintenance of sewage treatment equipment

Inappropriate operation management and lack of experience on maintenance of sewage treatment equipment in some sewage treatment plants has a negative effect on sewage reuse and industrial wastewater treatment, especially for alcohol, sugar and coffee processing. This is mainly due to the lack of funds to employ sufficient skilled labour to do the job.