title: Synergistic wetland treatment of sewage and mine water: pollutant removal performance of the first full-scale system.
abstract: Wetland systems are now well-established unit processes in the treatment of diverse wastewater streams. However, the development of wetland technology for sewage treatment followed an entirely separate trajectory from that for polluted mine waters. In recent years, increased networking has led to recognition of possible synergies which might be obtained by hybridising approaches to achieve co-treatment of otherwise distinct sewage and mine-derived wastewaters. As polluted discharges from abandoned mines often occur in or near the large conurbations to which the former mining activities gave rise, there is ample scope for such co-treatment in many places worldwide. The first full-scale co-treatment wetland anywhere in the world receiving large inflows of both partially-treated sewage (∼100 L s(-)(1)) and mine water (∼300 L s(-1)) was commissioned in Gateshead, England in 2005, and a performance evaluation has now been made. The evaluation is based entirely on routinely-collected water quality data, which the operators gather in fulfillment of their regulatory obligations. The principal parameters of concern in the sewage effluent are suspended solids, BOD5, ammoniacal nitrogen (NH4-N) and phosphate (P); in the mine water the only parameter of particular concern is total iron (Fe). Aerobic treatment processes are appropriate for removal of BOD5, NH4-N and Fe; for the removal of P, reaction with iron to form ferric phosphate solids is a likely pathway. With these considerations in mind, the treatment wetland was designed as a surface-flow aerobic system. Sample concentration level and daily flow rate date from April 2007 until March 2011 have been analyzed using nonparametric statistical methods. This has revealed sustained, high rates of absolute removal of all pollutants from the combined wastewater flow, quantified in terms of differences between influent and effluent loadings (i.e. mass per unit time). In terms of annual mass retention rates, for instance, the wetland system sequesters the following percentages of the key pollutants: BOD5: 41%; Fe 89%; NH4-N: 66%; dissolved P: 59%; total P: 46%; suspended solids: 66%. For similar wastewater chemistries, application of this type of co-treatment elsewhere could reasonably be based on the observed areally-normalized mass removal rates for the various pollutants found in this investigation.
authors.affiliation: Newcastle Institute for Research on Sustainability, Newcastle University, NE1 7RU, UK. Electronic address: paul.younger@glasgow.ac.uk.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Younger
authors.affiliation: School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Henderson
mesh_terms: D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D053833:Wetlands
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical
keywords: Mine water; Sewage; Treatment; Wetlands