Digested sludge from a municipal sewage treatment plant was systematically placed on the surface of pure diluvial sand in a forest plantation. In the area examined, sludge application started in September. Viruses could be demonstrated in the sludge deposits up to 21 weeks but not 22 weeks after the application. Polio-, coxsackie- and adenovirus types were detected. The method employed was elution with beef extract at pH 8 followed by hydroextraction. No virus was demonstrated in soil samples 5 weeks after sludge application. Ground water samples from bores established before sludge application were examined employing 5 litre samples, but these were all negative. Four larger samples (30 to 100 1) were examined. One 30 litre sample contained poliovirus type 2 and coxsackievirus type B3. It was collected in the 11th week after sludge application at a depth of 3 m under the surface. The 3 other samples were negative.
A soil sample of 30 kg collected at a depth of 35 to 100 cm was brought to the laboratory. Aliquots of 300 g were suspended in ground water from the area in flasks of 500 ml. Antibiotics were added. The pH was 4.5. In the same way a system employing a sandy loam soil was set up. Here the pH was 7.2. In each series 3 flasks were seeded with coxsackievirus B3, adenovirus 1 and echovirus 7 respectively. The flasks were completely filled with water, stoppered airtight and kept dark at 4° to 7°C. During an 8 month period 20 ml samples were taken 7 times after mixing. The samples were centrifuged. The supernatant and eluates of the sediments were examined for virus. Adenovirus was not demonstrated in the supernatants, echovirus only in the one from the sandy soil, while coxsackievirus was demonstrated in both supernatants. Except for adenovirus in the sandy loam soil the viruses were quite stable in the sediments. Ground water samples seeded with the same 3 viruses were set up in parallel but without added soil. The results obtained from these water samples were quite similar to the sediment samples except for echovirus which could not be demonstrated in the ground water from the sandy soil area after 2 months.
Leaching of heavy metals and nutrients from calcareous sandy-loam soil receiving municipal solid sewage sludge
