What factors make it difficult for Eastern Europe to improve its water quality?

eutrophication

greenhouse gases

outdated sewer systems

raw water quality

unskilled employees

worn-out water utilities

The factors that made it difficult for Eastern Europe to improve its water quality were outdated sewer systems, raw water quality, worn-out water utilities and unskilled employees. So we can say that four options given in the question fits the bill perfectly. These basic infrastructural reasons were responsible for being a hurdle towards improving the water quality.