Utilization of sewage sludge on land — Is it safe and economical?

A brief description of secondary sewage treatment in Hong Kong is given. Chemical analyses of the sludge produced by the major plants have indicated that the heavy-metal concentrations are relatively low and the fertilizer values are of the same order of those in the U.K. In the light of the U.K. guidelines regarding utilization of sludge on land, it has been concluded that sewage sludge can be utilized safely and economically in Hong Kong, most likely for landscaping and top soil where health risks are minimal.