Integrated Assessment of Groundwater Pollution from the Landfill of Sewage Sludge
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Federal State Budgetary Educational Institution of Higher Education “Saint-Petersburg State University”, 7-9 Universitetskaya emb., 199034, Saint-Petersburg, Russia
Scientific Research Center for Ecological Safety of the Russian Academy of Sciences, 18 Korpusnaya str.197110, Saint- Petersburg, Russia
Andrey Mikhailovich Dregulo   

Federal State Budgetary Educational Institution of Higher Education "Saint-Petersburg State University"
The purpose of this study was to assess the groundwater contamination from a sewage sludge landfill. The analysis was carried out in 2017 in accordance with the requirements of the national legislation for monitoring landfills and priority pollutants. The samples of groundwater from the landfill were taken from 25 observation wells, from depths of 45-60 m. The status and dynamics of changes in the landfill groundwater quality were estimated according to the data from the groundwater observation wells of the city observation network with regard to the chemical composition of groundwater and national standards of groundwater quality. The forecast estimates of a low level of pollutants entering groundwater through the soils characterized by low filtration properties were not justified. The concentration of heavy metals in groundwater was within the following range: Fe > Mn > Zn > Al > Cu > Ni > Pb > Cd > Hg. The excess concentration of the nitrogen-containing pollutants was observed within the range from 1.5 to 76 (on average 10 times) above the background value. The organic contamination of landfill groundwater (COD) is 2-9 times and BOD5 – 1.5-3 times higher than the average background value of groundwater observation wells in the city network. The probable cause for the pollutants entry into groundwater is associated with lithogenous and exogenous fracturing of the rocks and insufficient efficiency of the existing anti-filtration system of the landfill.