School of Physical and Chemical Sciences - Te Kura Matū Seminar Series

The removal of emerging organic contaminants from wastewater using constructed wetlands and carbonaceous bioreactors

Speaker

Morkel Zaayman

Institute

SPCS PhD Chemistry Candidate under the supervision of Sally Gaw

Time & Place

Mon, 21 Oct 2019 11:00:00 NZDT in Room 701, Level 7, WEST

All are welcome

Abstract

Emerging organic contaminants (EOCs) are a group of chemicals that include flame retardants, musks, personal care products, plasticisers, preservatives, steroid hormones, surfactants and UV blockers. A major pathway for EOCs into the environment is through the discharge of wastewater effluent into surface water bodies where they can have negative environmental effects. Constructed wetlands (CWs) are alternative wastewater treatment systems that are effective at treating wastewater for EOCs. This thesis aimed to 1) investigate the EOC removal efficiency of 6 hybrid constructed wetland (CW) treatment systems consisting of modules with various orientations, 2) identify which compounds were more likely to accumulate in the wetland substrates, and 3) determine the impact of the release of effluent from CW systems into the environment. Constructed wetlands were efficient at removing EOCs from wastewater, however the removal was dependent on the physicochemical properties of the contaminants, and the orientation of the modules. Major mechanisms from removal included biological degradation and sorption to suspended particulate with consequent filtration and retention in the wetland modules. Systems containing vertical flow sand and pea gravel modules, or active aeration were more effective at EOC removal than the horizontal flow treatment system. Different wetland substrates accumulated varying amounts of EOCs with the highest accumulation observed in horizontal flow modules. The accumulation of EOCs in the vertical flow modules was higher in the upper horizons, and the accumulation in the horizontal flow modules was higher in the lower horizons. Contaminants detected in the effluent from the CWs at concentrations high enough to pose an acute environmental threat included 4MBC, chloroxylenol, DEHP, galaxolide, OP, picaridin, tonalide and triclosan. The plasticiser DEHP was determined to be the only EOC that posed a chronic exposure risk.

 

All Welcome