1. Ph.D. Student, Dept. of Environmental Protection and Water Engineering, Vilnius Gediminas Technical Univ., Sauletekio al. 11, Vilnius LT-10223, Lithuania (corresponding author).
2. Professor, Dept. of Environmental Protection and Water Engineering, Institute of Environmental Protection, Vilnius Gediminas Technical Univ., Sauletekio al. 11, Vilnius LT-10223, Lithuania.