Päivi Karinen

Microbial Contamination of Groundwater at Small Community Water Supplies in Finland

The raw water quality and associations between the factors considered as threats to water safety were studied in 20 groundwater supplies in central Finland in 2002–2004. Faecal contaminations indicated by the appearance of Escherichia coli or intestinal enterococci were present in five small community water supplies, all these managed by local water cooperatives. Elevated concentrations of nutrients in raw water were linked with the presence of faecal bacteria. The presence of on-site technical hazards to water safety, such as inadequate well construction and maintenance enabling surface water to enter into the well and the insufficient depth of protective soil layers above the groundwater table, showed the vulnerability of the quality of groundwater used for drinking purposes. To minimize the risk of waterborne illnesses, the vulnerable water supplies need to be identified and appropriate prevention measures such as disinfection should be applied.

Maturity and hygiene quality of composts and hygiene indicators in agricultural soil fertilised with municipal waste or manure compost

Composts produced from municipal source separated biowaste (Biowaste), a mixture of biowaste and anaerobically digested sewage sludge (Biosludge) and cattle manure (Manure) were examined for their maturity and hygiene quality. The composts were applied to a potato crop in 2004 and to a barley nurse crop of forage ley in 2005 in a field experiment. Numbers of faecal coliforms, enterococci, clostridia and Salmonella in field soil were determined 2 weeks and 16 weeks after compost applications. Municipal compost batches chosen based on successful processing showed variable maturity during field application, and the need to evaluate compost maturity with multiple variables was confirmed. The numbers of faecal coliform were similar in all compost types, averaging 4.7 and 2.3 log 10 CFU g-1 in the first and second years, respectively. The highest number of enterococci was 5.2 log10 CFU g-1, found in Manure compost in the first year, while the highest clostridia numbers were found in Biosludge compost, averaging 4.0 log10 CFU g -1 over both years. Except for one case, less than 2.4 log10 CFU g-1 of faecal coliforms or clostridia were found in compost-fertilised soil, while the numbers of enterococci were mostly higher than in unfertilised soil (<4.2 or <3.2 log10 CFU g-1, respectively). No hygiene indicator bacteria were present in compost-fertilised potato at harvest. Overall, compost fertilisations caused rather small changes in the counts of hygiene indicators in the field environment.