Evaluation of Constructed Wetlands and Pretreatment Options For the Treatment of Flow-through Trout Farm Effluent

Horizontal subsurface flow (HSSF) constructed wetlands were evaluated for the treatment of flow-through trout farm effluent, phosphorus sorption affinity of gravel-bed media, and influence on Rhodamine WT (RWT) transport. HSSF wetlands coupled with mechanical pretreatment demonstrated significant (p <0.05) removal of total ammonia-nitrogen (TAN), total phosphorus (TP), total organic carbon (TOC), total suspended solids (TSS), five-day biochemical oxygen demand (BOD5), and turbidity. Treatment occurred predominantly within the wetland cells, with minimal removal of studied water quality parameters by means of sedimentation or microscreen filtration (80 ?m mesh). HSSF wetlands removed 69% of influent TSS, 24% of influent TP, and reduced turbidity by 66%. The removal of organic matter within the wetlands, as measured by BOD5, COD, and TOC was 62%, 50%, and 55%, respectively. After receiving effluent from a flow-through trout farm for about one year, the gravel media exhibited moderate removals of soluble phosphorus in batch and column sorption experiments. Partition coefficients (Kd) from batch sorption tests ranged from 45-90 mL/g. Low (60 mL/min) and high (165 mL/min) flow column experiments removed about 50 and 40% of influent PO4-P, respectively. The conservative nature of RWT in subsurface media has been called into question by many authors. Tracer response curves from tests conducted in pilot-scale HSSF wetlands exhibited elongated tails and dual peaks, in addition to mean tracer retention times far exceeding the theoretical value. Laboratory column testing of RWT and the more conservative NaCl tracer supported field data, indicating that RWT was more reactive within the wetland media.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Environmental Planning

Department dc:contributor.department

Environmental Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2011

Author dc:creator

• Doheny, Ryan Matthew

Chair dc:contributor.committeechair

• Boardman, Gregory D.

Committee members dc:contributor.committeemember

• Scardina, Robert P.
• Hession, W. Cully

• constructed wetlands
• sedimentation basin
• microscreen
• Rhodamine WT
• Phosphorus

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Dc Identifier Other

etd-07152011-230705

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/76824