Limiting the emissions of micro-pollutants: what efficiency can we expect from wastewater treatment plants?

摘要

The next challenge of wastewater treatment is to reliably remove micro-pollutants at thenmicrogram per litre range in order to meet the environmental quality standards set by newnregulations like the Water Framework Directive. The present work assessed the efficiency ofndifferent types of primary, secondary and tertiary processes for the removal of more thann100 priority substances and other relevant emerging pollutants through on-site mass balancesnover 19 municipal wastewater treatment lines. Secondary biological processes proved to be innaverage 30% more efficient than primary settling processes. The activated sludge (AS) processnled to a significant reduction of pollution loads (more than 50% removal for 70% of thensubstances detected). Biofilm processes led to equivalent removal efficiencies compared to AS,nexcept for some pharmaceuticals. The membrane bioreactor (MBR) process allowed to upgradenremoval efficiencies of some substances only partially degraded during conventional ASnprocesses. Preliminary tertiary processes like tertiary settling and sand filtration could achievensignificant removal for adsorbable substances. Advanced tertiary processes, like ozonation,nactivated carbon and reverse osmosis were all very efficient (close to 100%) to complete thenremoval of polar pesticides and pharmaceuticals; less polar substances being better retained bynreverse osmosis.