Phosphorus Removal by Expanded Clay—Six Years of Pilot‐Scale Constructed Wetlands Experience

Abstract

Constructed wetlands, which facilitate phosphorus removal via precipitation, adsorption, and biological assimilation, offer a promising appropriate technology for advanced treatment in wastewater treatment plants. Because adsorption and precipitation are pointed out as the major phosphorus-removal mechanisms, the selection of a medium with high phosphorus-sorption capacity is important to obtain a sustained phosphorus removal. The objective of this study was to evaluate two kinds of lightweight expanded clay aggregates (LWAs)-Filtralite NR and Filtralite MR (Maxit Group, Avelar, Portugal)-as substrates in constructed wetlands to improve phosphorus-removal performance. Laboratory experiments were performed to test the potential of the LWAs to remove phosphorus from a phosphate solution. The experimental data were wellfitted by both the Langmuir and Freundlich isotherm models. Pilot-scale investigations were carried out to evaluate the phosphorus removal under field conditions. Four subsurface constructed wetlands were operated since June 2002; two of them were planted with Phragmites australis, and the other two were unplanted. The beds were filled with the two kinds of LWAs. Total phosphorous and pH were monitored since 2003, at a mean hydraulic load of 50 6 4 L/(m 2 ?d), during 6 years. The inflow phosphorus concentration was in the range 4 to 13 mg/L. Under the conditions used, beds with Filtralite MR had better efficiency, and the bed with Filtralite MR planted with Phragmites australis provided a phosphorus effluent mean concentration of 0.7 6 0.2 mg/L, during the trial period. This study presents the first long-term pilot-scale data for constructed wetlands using LWAs. Water Environ. Res., 82, 128 (2010).

The Potential Growth of Sugarcane in Constructed Wetlands Designed for Tertiary Treatment of Wastewater

“…However, in general, direct comparison experiments between planted and unplanted CW give results similar to the present work-planted CWs performed better than unplanted CWs [32,[46][47][48][49]. Among the possible roles of plants in the wastewater treatment processes, the roots surface support for microbial film development and the provided oxidized rhizosphere were pointed out as the principal plants contributions [37,42,50,51].…”

“…They are close to 90% TP removal for CW T1, and 80% TP removal for CW T3. This range of values, and the average removal efficiencies (Table 1), are well comparable to the efficiency obtained in the same climate and with the same operational conditions for CWs planted with the traditional macrophyte Phragmites australis and filled with high phosphorous removal capacity expanded clays [32]. The proportion of input P sequestered in the plant´s aerial parts was 9.2% for CW T1 and 6.3% for CW T3.…”

“…The results for the two type of filling media are only slightly significantly different (p = 0.042). For both types of filling materials, the plants' average contribution for TP removal from the wastewater throughout the experiment period is 9%, which is a typical value for the usual CW vegetation [32][33][34].…”

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

“…Recently, despite the slightly increased cost of production, processed clay materials have also become popular choices for CWS substrates and in any case clay-based materials proved to be an adequate medium for a good performance of CWS [42,46,47,83,84,126,165,[199][200][201][202][203][204][205][206].…”

The Adsorptive Properties of Fired Clay Pellets for the Removal of Phosphate in Wastewater Treatment

“…Excessive or elevated nutrients in the water system may enhance the increase in plant based organic matter hence causing eutrophication and algal blooms [1,2,3,4,5]. Phosphate has been cited as a vital and limiting nutrient in freshwater system and has been suggested that a decrease in phosphate can effectively control eutrophication in coastal and fresh water systems [2,6,7].…”