Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance

a b s t r a c tNine filter beds have been constructed in the Nordic countries, Denmark, Finland, Norway and Sweden. Filter beds consist of a septic tank followed by an aerobic pre-treatment biofilter and a subsequent saturated flow grass-covered filter. Thus, filter beds are similar to subsurface flow constructed wetlands with pre-treatment biofilters, but do not have wetland plants with roots submerged into the saturated filter. All saturated filters contain Filtralite ® P, a light-weight expanded clay aggregate possessing high phosphorus sorption capacity. The filter bed systems showed stable and consistent performance during the testing period of 3 years. Removal of organic matter measured as biochemical oxygen demand (BOD) was >80%, total phosphorus (TP) >94% and total nitrogen (TN) ranged from 32 to 66%. Effluent concentrations of fecal indicator bacteria met the European bathing water quality criteria in all systems. One system was investigated for virus removal and somatic viruses were not detected in the effluent. The investigations revealed that the majority of the BOD and nitrogen removal occurred in the pre-treatment filters and the phosphorus and bacteria removal was more prominent in the saturated filters. The saturated filters could be built substantially smaller than the current design guidelines without sacrificing treatment performance. The used filter material met the Norwegian regulations for reuse in agriculture with respect to heavy metals, bacteria and parasites. When saturated with phosphorus, the light-weight aggregate, Filtralite ® P used in the saturated bed is a suitable phosphorus fertilizer and additionally has a liming effect.

Section: Introductionsupporting

confidence: 58%

Filter bed systems treating domestic wastewater in the Nordic countries – Performance and reuse of filter media

Jenssen

Krogstad

Paruch

et al. 2010

“…velocities, increasing the opportunity time for N-processing and surface sedimentation (Brix, 95 1997). Thus, the use of emergent macrophytes in CTWs to provide beneficial services is 96 becoming increasingly important to water resource managers (Thullen et al, 2005). 97…”

mentioning

confidence: 99%

Aridland constructed treatment wetlands I: Macrophyte productivity, community composition, and nitrogen uptake

Weller

Childers

Turnbull

et al. 2016

Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Ecological Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in Ecological Engineering, December 2016December , 97, 649-657, 10.1016December /j.ecoleng.2015 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Urbanized areas increasingly rely on constructed treatment wetlands (CTW) for cost 9 effective and environmentally-based wastewater treatment. Constructed treatment wetlands are 10 particularly attractive treatment options in arid urban environments where water reuse is 11 important for dealing with scarce water resources. Emergent macrophytes play an important role 12 in nutrient removal, particularly nitrogen (N) removal, in CTW. However, the role of plant 13 community composition in nutrient removal is less clear. Numerous studies have shown that 14 macrophyte species differentially affect N uptake processes (e.g.: direct plant uptake, coupled 15 nitrification-denitrification, soil accretion). However, many of these studies have been based on 16 small-scale experiments and have been carried out in mesic environments, which means that 17 their findings are difficult to extrapolate to aridland CTW systems. Our study sought to examine 18 the relationships among emergent macrophyte productivity, plant community composition, and 19 N uptake [by both the plants and the entire ecosystem] at a 42 ha CTW in arid Phoenix, Arizona, 20 USA. We quantified above-and belowground biomass bimonthly and foliar N content annually 21 for four species groups (Typha latifolia + T. domingensis., Schoenoplectus californicus + S. 22 tabernaemontani, Schoenoplectus acutus, and Schoenoplectus americanus) from July 2011 to 23 September 2013. We quantified dissolved inorganic N fluxes into and out of the system and 24 compared plant N removal to total system fluxes. Additionally, we estimated monotypic N 25 content for each to compare the system's current community composition and plant N removal to 26

“…Long-term processes, such as nutrient removal through sedimentation and storage, are compromised by the short-term benefits of dredging (i.e., higher water storage capacity). Nutrient removal might be further improved by providing additional habitat in the form of contours, hummocks, and graded banks for a high diversity of species that would assimilate nutrients from both the water column and the sediment (Greenway, 2005;Thullen et al, 2005).…”

Section: Management and Design Considerationsmentioning

confidence: 99%

Tropical treatment wetlands dominated by free-floating macrophytes for water quality improvement in Costa Rica

Nahlik

Mitsch

2006

145

a b s t r a c tFive tropical treatment wetlands dominated by floating aquatic plants and constructed to deal with a variety of wastewaters were compared for their effectiveness in treating organic matter and nutrients in the Parismina River Basin in eastern Costa Rica. Wastewaters were from a dairy farm, a dairy processing plant, a banana paper plant, and a landfill. Four of the five wetland systems were effective in reducing nutrient levels of effluents before water was discharged into rivers. Ammonia levels in water entering most wetlands were considerably higher than ambient (i.e., riverine) levels; concentrations were reduced by as much as 92% in the wetlands and retained at a maximum rate of 166 g N m −2 year −1 .Nitrate nitrogen removal was variable, but occurred in low concentrations in the inflows (less than 1 mg N L −1 ). Phosphate phosphorus was present in high levels but was effectively reduced through the wetlands (92 and 45% reductions through dairy farm wetlands, 83% reduction through banana paper wetlands, and 80% reduction through dairy processing wetlands). Retention of phosphate phosphorus ranged from 0.1 to 10.7 g P m −2 year −1 in the treatment wetlands. Dissolved oxygen in the wetland outflows were ≤2 mg L −1 in three of the sampled wetlands, most likely a result of the abundant free-floating macrophytes that sheltered the water from diffusion and shaded aquatic productivity. The efficacy of these created wetlands to treat effluents from different sources varied, and modified wetland designs or active management may be necessary to improve water quality even further.Recommendations on tropical wetland design and management are presented, as are suggestions for implementing this ecological engineering approach with farmers in Central America.