Investigation of pre-treatment influence to excess sludge digestion processBlonskaja, Viktoria; Vaalu, Tarmo"Environmental Impact and Water Management in a Catchment Area Perspective" : 24-26 September, 2001, Tallinn, Estonia : proceedings of the Symposium dedicated to the 40th Anniversary of Institute of Environmental Engineering at Tallinn Technical University2001 / p. 223-231 : ill