Active slag filters: rapid assessment of phosphorus removal efficiency from effluent as a function of retention time

Abstract

There is increasing pressure to upgrade effluent ponds for phosphorus removal. Active slag filters offer a solution, but design information is limited. Hydraulic retention time (HRT) is a key factor in filter design because it controls filter treatment efficiency as well the filter substrate lifespan. This paper reports on a rapid method of continual looping of effluent through a filter column to obtain a relationship between HRT and phosphorus removal efficiency. Phosphorus removal declined logarithmically with respect to retention time. While the mechanisms that yield this relationship involve complex mass transfer and adsorption of phosphorus to Fe oxyhydroxide sites, in general terms, the adsorption rate is proportional to the adsorbate effluent concentration. Waste stabilization pond effluent treated by the slag achieved phosphorus removal efficiencies over 90% at extended HRTs greater than 70 hours, while 80% removal was obtainable in 30 hours. Higher phosphorus removal was achieved for slag treating real effluent compared with synthetic phosphate solution. This can be explained by: (1) different starting phosphorus concentrations in the synthetic phosphate solution and real effluent; and (2) the presence of constituents in real effluent that can enhance phosphorus removal, such as oxidized iron compounds, cations, algae and humic complexes. This new technique, which proved capable of replicating treatment efficiencies obtained from long-term column studies, offers rapid assessment of phosphorus removal efficiency as a function of retention time and thus will enable design engineers to size active filters on the basis of achieving the required phosphorus removal standards.

Reliability analysis of nutrient removal from stormwater runoff with green sorption media under varying influent conditions

“…Due to these processes, sorption is temporally dependent (Barrow, 1978). For many wetland treatment systems, phosphorus removal increases with increasing hydraulic retention time (HRT) (Tang et al, 2008), although for an active slag filter, phosphorus removals declined logarithmically with respect to retention time (Shilton et al, 2013). For materials such as quartz sand, anthracite, and shale, It was found that adsorption occurred within short contact times (less than 2 h) and after which adsorption remained constant (Jiang et al, 2014).…”

Using Steel Slag for Dissolved Phosphorus Removal: Insights from a Designed Flow-Through Laboratory Experimental Structure

“…These PSMs are often byproducts of industrial or natural origin, such as steel slag [6], drinking water and mine drainage residuals [7], fly ash [8], bauxite waste [9], Fe oxides [10], and gypsum [11], which are rich in calcium, aluminum, or iron. The main mechanism for removing P is through adsorption onto metal oxides and oxyhydroxides, and precipitation as calcium phosphates, thus transforming dissolved P into an insoluble state [12][13][14]. A P removal structure constructed with PSMs is considered an engineering technology for reducing P loss.…”

Vegetated Steel Slag Substrate Constructed Wetlands can Achieve High Efficiency Simultaneous Nitrogen and Phosphorus Removal

“…Next, not all articles could be employed for further analysis because they were review articles, and certain articles did not contain data on N and P removal amounts. By reading the title, abstract, and text of the articles during screening, 27 articles (Huang and He, 2011;Wu et al, 2011;Xiong et al, 2011;Barca et al, 2013;Shilton et al, 2013;Barca et al, 2014;Ren et al, 2014;Shi et al, 2014;Cui et al, 2015;Ge et al, 2015;Hussain et al, 2015;Yun et al, 2015;Zhang et al, 2015;Blanco et al, 2016;Ge et al, 2016;Lu et al, 2016;Mohamed et al, 2016;Ahmad et al, 2017;Shi P. et al, 2017;Park et al, 2017;Yuan et al, 2017;Adera et al, 2018;Xu et al, 2019;Chen et al, 2020;Hamdan et al, 2020;Saeed et al, 2020;Wan et al, 2020) met our requirement and were finally selected for data analysis, which provided a highly uniform dataset and reliable results. Datasets of the substrate filling mode, plant cultivation, flow direction of CW, steel slag particle size (SSPS), temperature (T), hydraulic retention time (HRT), hydraulic loading rate (HLR), pH value (pH), influent concentration (C in ), total nitrogen (TN), NH 4 + -N, and TP removal amounts (ΔC = C in − C out ) were extracted from these articles, and some original data were modified.…”

“…In the initial application stage, SSCWs stuffed with single steel slag as substrate were used to remove P from sewage with different P concentrations. Following that, SSCWs with a combined and modified substrate were used to comprehensively improve the quality of septic tank sewage (Huang and He, 2011;Hussain et al, 2015), domestic sewage (Wu et al, 2011;Yun et al, 2015;Mohamed et al, 2016;Hamdan et al, 2020), urban sewage (Barca et al, 2013), pond sewage (Shilton et al, 2013), secondary effluent of sewage treatment plants (Xiong et al, 2011;Zhang et al, 2015;Chen et al, 2020), polluted river waters (Shi et al, 2014;Ge et al, 2015;Ge et al, 2016), hydroponic sewage (Park et al, 2017), agricultural sewage (Lu et al, 2016;Yuan et al, 2017), dairy farm sewage (Adera et al, 2018), leachate (Saeed et al, 2020), and other sewage. Besides, SSCWs demonstrate high P recovery potential.…”

“…Subsurface SSCWs are most widely used according to the flow direction and are divided into unsaturated vertical flow (Huang and He, 2011;Wu et al, 2011;Xiong et al, 2011;Shilton et al, 2013;Ren et al, 2014;Shi et al, 2014;Cui et al, 2015;Hussain et al, 2015;Zhang et al, 2015;Blanco et al, 2016;Ge et al, 2016;Lu et al, 2016;Mohamed et al, 2016;Ahmad et al, 2017;Yuan et al, 2017;Adera et al, 2018;Hamdan et al, 2020;Saeed et al, 2020) and saturated horizontal flow (Barca et al, 2013;Barca et al, 2014;Ren et al, 2014;Cui et al, 2015;Ge et al, 2015;Park et al, 2017;Yuan et al, 2017;Adera et al, 2018;Xu et al, 2019;Chen et al, 2020) SSCWs. Next, vertical flow SSCWs require only a small amount of ground to operate but provide appropriate contact time and anaerobic time between water and substrate to ensure a better nitrogen and phosphorus removal performance (Yun et al, 2015).…”