Vertical-flow constructed wetlands treating domestic wastewater contaminated by hydrocarbons

• Published in: Water science and technology 2015-01, Vol.71 (6), p.938-946
• Main Authors: Al-Isawi, R H K, Sani, A, Almuktar, S A A A N, Scholz, M
• Format: Article
• Language: English
• Subjects: Aggregates; Ammonia; Ammonium Compounds - analysis; Aquatic plants; Artificial wetlands; Biochemical oxygen demand; Chemical oxygen demand; Chemical spills; Contamination; Data analysis; Diesel; Diesel fuels; Domestic wastewater; Efficiency; Filters; Filtration; Fluid filters; Freshwater plants; Gasoline - analysis; Health sciences; Hydraulics; Hydrocarbons; Inflow; Laboratories; Marshes; Methods; Nitrates - analysis; Nitrogen; Organic chemicals; Outflow; Petroleum hydrocarbons; Petroleum Pollution - analysis; Phosphates; Phosphates - analysis; Phosphorus; Phragmites australis; Removal; Seasons; Secondary wastewater; Secondary wastewater treatment; Suspended particulate matter; Suspended solids; Tidal currents; Tidal flow; Total oxygen demand; Waste Disposal, Fluid; Waste Water - analysis; Wastewater; Wastewater pollution; Wastewater treatment; Water Pollutants, Chemical - analysis; Water Quality; Wetlands
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2015.054

The aim was to compare the impact of different design (aggregate size) and operational (contact time, empty time and chemical oxygen demand (COD) loading) variables on the long-term and seasonal performance of vertical-flow constructed wetland filters operated in tidal flow mode before and after a one-off spill of diesel. Ten different vertical-flow wetland systems were planted with Phragmites australis (Cav.) Trin. ex Steud. (common reed). Approximately 130 g of diesel fuel was poured into four wetland filters. Before the spill, compliance with secondary wastewater treatment standards was achieved by all wetlands regarding ammonia-nitrogen (NH4-N), nitrate-nitrogen (NO₃-N) and suspended solids (SS), and non-compliance was recorded for biochemical oxygen demand and ortho-phosphate-phosphorus (PO₄-P). Higher COD inflow concentrations had a significantly positive impact on the treatment performance for COD, PO₄-P and SS. The wetland with the largest aggregate size had the lowest mean NO₃-N outflow concentration. However, the results were similar regardless of aggregate size and resting time for most variables. Clear seasonal outflow concentration trends were recorded for COD, NH4-N and NO₃-N. No filter clogging was observed. The removal efficiencies dropped for those filters impacted by the diesel spill. The wetlands system shows a good performance regarding total petroleum hydrocarbon (TPH) removal.