Phosphate and ammonium removal from waste water, using constructed wetland systems

Phosphorus and nitrogen in waste water from sewerage systems contribute to excessive nutrient enrichment of surface waters, presenting a threat to nature conservation, domestic and industrial water supplies, and recreation. The general objective of this research was to investigate phosphate and ammonium removal from waste water by constructed wetland systems (CWS), which are increasingly being used for low-cost water treatment. Phosphate (P) adsorption capacity and other properties of potential CWS substrate materials (bauxite, shale, burnt oil shale, limestone, zeolite, light expanded clay aggregates (LECA) and fly ash) were investigated. Fly ash and shale had the highest P adsorption values, which were significantly correlated with porosity and hydraulic conductivity. Longer - term experiments with shale and bauxite gave maximum P uptake values of 730 and 355 mg P kg- I, respectively. Phragmites australis (common reed) seedlings grew satisfactorily in shale, bauxite, LECA and fly ash. Shale was selected as the most suitable substrate, and used in a pilot-scale CWS in plastic tanks in a greenhouse, with and without P. australis, at two input nutrient concentrations and a loading rate of 0.02 m3 m-2 d-1. Both planted and unplanted systems removed 98 - I 00% of P from a synthetic sewage over ll months. Removal of ammonium N was also complete in the planted tanks, but only 40 - 75% was removed in the unplanted ones. Corresponding nitrate N removal was 85 - 95% and 45 - 75%. The systems performed as well at high as at low concentration for both phosphate and ammonium. The variations in P and N removal could not be attributed to differences in pH, Eh and temperature, which did not differ significantly between planted and unplanted tanks. During the experiment, P and N concentrations were determined at 3 depths and 4 positions along the length of the tanks. H2P04- - P and NH/ - N concentrations were low ( < I. 0 g m-3) at all locations in the planted systems, whereas the P concentrations were sometimes twice as high in the unplanted ones. NH4 + -N in the unplanted systems was relatively high (l 0 - 30 g m"3) throughout the experiment. N03--N concentrations were very low by comparison. P. precipitation on shale and P. australis root and rhizome surfaces was examined by X-ray fluorescence analysis, and by chemical extraction with ammonium acetate, 0.1 M HCI and 2%> citric acid. This showed that P, Fe and Al had precipitated on all these surfaces. However. it was not possible to quantify the surface deposits, and further research is necessary. The hydraulic residence time. flow characteristics and permeability of the shale was investigated by a bromide tracer. The tracer breakthrough curves showed a similar pattern in all tanks, with ca 66% of the flow occurring through the bottom zone. However, the actual hydraulic residence time (6 days) was slightly higher than the theoretical one Although there was a significant difference (p < 0.02) between the distribution of flow in planted and unplanted tanks. there was no reduction in the reactive pore volume observed in any of the tanks. This confirmed that shale has good permeability properties. Monitoring of the full-scale systems was carried out during June - September 1995. Although P removal in a planted bed was between 50-75%, the overall performance of the full-scale systems was disappointing, especially for ammonium removal. This was attributed to high loading rates, visibly non-uniform flow and clogged gabions. A bromide tracer study carried out on these systems confirmed the short hydraulic retention times and heterogeneous flow mechanisms in both the unplanted and planted systems. Results obtained from the pilot scale study do not necessarily provide a quantitative prediction of the performance of larger-scale systems. However, the potential value of a shale-based system has been demonstrated, and this opens a new direction in the design of CWS; most systems built to date in the UK use gravel as a substrate. Shale has proved to have superior properties for P removal and is cheap and readily available in Scotland. Its application as a substrate in a full-scale system remains a subject for further investigation

Effect of organic load on phosphorus and bacteria removal from wastewater using alkaline filter materials

AbstractThe organic matter released from septic tanks can disturb the subsequent step in on-site wastewater treatment such as the innovative filters for phosphorus removal. This study investigated the effect of organic load on phosphorus (P) and bacteria removal by reactive filter materials under real-life treatment conditions. Two long-term column experiments were conducted at very short hydraulic residence times (average ∼5.5 h), using wastewater with high (mean ∼120 mg L−1) and low (mean ∼20 mg L−1) BOD7 values. Two alkaline filter materials, the calcium-silicate material Polonite and blast furnace slag (BFS), were tested for the removal capacity of total P, total organic carbon (TOC) and Enterococci. Both experiments showed that Polonite removed P significantly (p < 0.01) better than BFS. An increase in P removal efficiency of 29.3% was observed for the Polonite filter at the lower concentration of BOD7 (p < 0.05). Polonite was also better than BFS with regard to removal of TOC, but there were no significant differences between the two filter materials with regard to removal of Enterococci. The reduction in Enterococci was greater in the experiment using wastewater with high BOD7, an effect attributable to the higher concentration of bacteria in that wastewater. Overall, the results demonstrate the importance of extensive pre-treatment of wastewater to achieve good phosphorus removal in reactive bed filters and prolonged filter life

Constructed Wetlands for Agricultural Wastewater Treatment in Northeastern North America:A Review

Constructed wetlands (CW) are a treatment option for agricultural wastewater. Their ability to adequately function in cold climates continues to be evaluated as they are biologically active systems that depend on microbial and plant activity. In order to assess their performance and to highlight regional specific design considerations, a review of CWs in Eastern Canada and the Northeastern USA was conducted. Here, we synthesize performance data from 21 studies, in which 25 full-scale wetlands were assessed. Where possible, data were separated seasonally to evaluate the climatic effects on treatment performance. The wastewater parameters considered were five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), E. coli, fecal coliforms, total Kjeldahl nitrogen (TKN), ammonia/ammonium (NH3/NH4+-N), nitrate-nitrogen (NO3−-N), and total phosphorus (TP). Average concentration reductions were: BOD5 81%, TSS 83%, TKN 75%, NH4+-N 76%, NO3−-N 42%, and TP 64%. Average log reductions for E. coli and fecal coliforms were 1.63 and 1.93, respectively. Average first order areal rate constants (ka, m·y−1) were: BOD5 6.0 m·y−1, TSS 7.7 m·y−1, E. coli 7.0 m·y−1, fecal coliforms 9.7 m·y−1, TKN 3.1 m·y−1, NH4+-N 3.3 m·y−1, NO3−-N 2.5 m·y−1, and TP 2.9 m·y−1. In general, CWs effectively treated a variety of agricultural wastewaters, regardless of season

EAF steel slag filters for phosphorus removal from milk parlor effluent: the effects of solids loading, alternate feeding regimes and in-series design

Electric arc furnace (EAF) steel slag filters were investigated for their efficiency at reducing the concentration of phosphorus (P) from dairy farm wastewater in Vermont. The primary objective for this study was to examine the use of in series design on filters’ performance in P removal from dairy farm wastewater at subzero temperatures. Other research objectives were to investigate operational parameters such as the effects of total suspended solids (TSS) daily mass loading rates and of alternating feeding and resting periods on EAF steel slag filters’ TSS, dissolved reactive phosphorus (DRP) and total phosphorus (TP) removal efficiencies and filter system life-span. The utilization of in series filter design increased filter DRP removal efficiency by 35%. In series design also allows for alternating feeding and resting periods, which resulted in a 16%, 57% and 74% increase in TSS, DRP and TP removal efficiencies, respectively, by the first filter in series over a single period. Additionally, the system life span was extended 3.25 fold (from 52 to 169 day). Based on this research, we recommend alternate feeding and resting cycles and in series design to be integrated in the design of EAF steel slag filter systems for highly concentrated agricultural effluents in cold climates

An Inventory of Good Management Practices for Nutrients Reduction, Recycling and Recovery from Agricultural Runoff in Northern Periphery and Arctic (NPA) region

Publication history: Accepted - 26 June 2022; Published online - 4 July 2022The excess loading of nutrients generated by agricultural activities is a leading cause of water quality impairment across the globe. Various management practices have been developed and widely implemented as conservation management strategies to combat water pollution originating from agricultural activities. In the last ten years, there has also been a widespread recognition of the need for nutrient harvesting from wastewaters and resource recovery. In Europe’s Northern Periphery and Arctic (NPA) areas, the expertise in water and runoff management is sporadic and needs to be improved. Therefore, the objective of this research was to perform a comprehensive review of the state of the art of Good Agricultural Practices (GAPs) for the NPA region. A set of questionnaires was distributed to project partners combined with a comprehensive literature review of GAPs focusing on those relevant and/or implemented in the NPA region. Twenty-four GAPs were included in the inventory. This review reveals that there is a large level of uncertainty, inconsistency, and a gap in the knowledge regarding the effectiveness of GAPs in nutrient reduction (NRE), their potential for nutrient recycling and recovery (NRR), and their operation and maintenance requirements (OMR) and costs. Although the contribution of GAPs to water quality improvement could not be quantified, this inventory provides a comprehensive and first-of-its-kind guide on available measures and practices to assist regional and local authorities and communities in the NAP region. A recommendation for incorporating and retrofitting phosphorus retaining media (PRMs) in some of the GAPs, and/or the implementation of passive filtration systems and trenches filled with PRMs to intercept surface and subsurface farm flows, would result in the enhancement of both NRE and NRRThis research was funded by the European Union European Research Development Fund Northern Periphery and Arctic Programme 2014–2020, grant number 304-2559-2016