The costs for personnel of wastewater treatment systems depend significantly on the size of the treatment plant, the selected technology and the level of automation. The table below shows the personnel costs subject to the treatment capacity of wastewater treatment plants [Reicherter, 2003].

Costs for personnel normally comprises salaries/wages, pension and insurance costs. A typical working week consists of five working days per week, with a month’s leave over a year. Depending on a system’s requirements, there can be one, two or three eight-hour shifts for specific position. The operation personnel mainly is occupied with activities related to process control, in average 30 % of the working time is spend for maintenance activities. The cost to the employer of an annual salary including insurance depend on the wage level of each state or district, in which a treatment facility is located.

Kemper et al (1994) showed that in developing countries the cost of personnel in the wastewater treatment sector is proportionately higher than for developed countries. In average in Greece the cost of personnel is 48% of the total cost for operation of a treatment plant. For France the figure is 24 %, for Great Britain 38%. On the other hand, in Mexiko and Costa Rica, personnel costs are 68% of the total.

The qualification of operation staff is of crucial importance for an adequate and professional operation. There is a high need for a profound education and special training as a essential prerequisite. Plant operators can make a plant of poor and insufficient design perform well, conversely, they can cause the best design plant to perform poorly [Michel et al., 1969]. Smaller treatment plants employ fewer scientific personnel and fewer unskilled laborers, with higher number of technical personnel. There are likely to be two reasons for this: At first because small treatment plants are less complicated and easier to operate, secondly for small towns it is difficult to find higher educated personnel with scientific education, relying instead on local personnel.

Chemical engineers and chemists are the most dominant graduate employees in wastewater treatment plants. Chemical, electrical and mechanical engineers mainly work as control engineers, while technologists are in charge of the technical supervision. Technologists come from technical colleges which do not have university status. Ideally, a wastewater treatment plant would have an input from all kind of professionals. However, this is unfeasible for all but the very large installations and for centralized agencies with a number of plants under their jurisdiction.