Phosphorus Adsorption Capacity Evaluation for the Substrates Used in Constructed Wetland Systems: a Comparative Study

Abstract

CWs have been designed and constructed to use natural processes for the removal of pollutants from contaminated water in a more controlled environment [1][2][3]. Previous results have shown that substrate adsorption plays the most important role in P immobilization [4][5][6][7][8]. Therefore, cheap and effective P adsorbents are highly desirable [9][10][11].The most commonly used substrates in CWs are quartz sands [12], activated carbon (AC) [12][13], zeolite [14], ceramic [15], and furnace slag [16][17], and prior research has shown that the removal of P by these substrates mainly occurs though physical adsorption, chemical precipitation, and ion exchange [10][11]. However, P sorption properties of the substrates have not been systematically estimated, which resulted in many defective packing layer designs for CWs [3,11]. Thus, it is important to evaluate the P adsorption properties of the substrates before full-scale use was performed.Pol. J. Environ. Stud. Vol. 26, No. 3 (2017) AbstractTo provide a selection criteria to choose substrates according to the quality of the water requiring treatment in constructed wetlands (CWs), phosphorus (P) adsorption properties of four quartz sands with different physicochemical characteristics and four substrates commonly used in CWs were tested and evaluated via both the Langmuir and Freundlich equations. The effects of organic maters (OM) on P adsorption capacities of the substrates were also studied to evaluate the practical values of the substrates. The Langmuir sorption isotherm was used to estimate the P adsorption capacities of the tested substrates in CWs. Overall, the maximum P adsorption for all of the tested substrates decreased as follows: furnace slag > ceramic > zeolite > activated carbon > quartz quartz sands. The P adsorption capacities were significantly influenced by grain size; specific surface area; Fe, Al, Mg, and Ca contents in the substrates; and the amount of added OM. The chemical precipitation of P by the substrates containing Fe was more effective than those containing Ca at the same level. Added OM impacts P sorption by influencing pH, and substrates containing higher Fe and Al concentrations and lower Ca concentrations were more resistant to decreases in the P adsorption capacities due to OM accumulation. Finally, a principle for selecting substrates for the treatment of wastewater with different characteristics was determined.

Potential Application of Chilean Natural Zeolite as a Support Medium in Treatment Wetlands for Removing Ammonium and Phosphate from Wastewater

“…The behavior of the adsorption process of NH 4 + -N and PO 4 −3 -P could be described for Chilean natural zeolites through two adsorption models: Saturation-growth-rate and Langmuir (Table 5, Figure 3, Table 6). The results are similar to the results reported for other materials studied to be used as support mediums in treatment wetlands [9,32,53]. In addition, the results of this study confirm that Chilean natural zeolites can be used for both N and P removal from wastewater (including those produced in rural areas) and that their potential application as a support medium for treatment wetlands is similar to that of other natural zeolites previously used for this purpose [30,40,54].…”

The Research on the Effects of Substrate Types Using for Constructed Wetland

“…Ceramsite has the advantages of strong adsorption capacity, good chemical stability, easy regeneration, environmentally friendly, and low price. Its specific surface area was very favorable to the growth of microorganisms and reflects a better removal effect on both nutrient salts and organic matter [8].…”

Seeded phosphorus retention in fixed-bed laboratory columns by the use of apatites

“…Phosphorus removal in small wastewater treatment plants (WWTPs) is a technological issue yet to be resolved (Vohla et al, 2011). A large number of substrates for phosphorus retention have already been assessed using batch or laboratory-column experiments (Cui et al, 2008;Dai and Hu, 2017;Barca et al, 2021;Perez et al, 2021) or at the pilot scale, while full-scale applications have not been adequately developed or studied (Shilton et al, 2006). The use of filters with reactive substrates, such as natural apatites (Ca 5 (PO 4 ) 3 (OH,F,Cl)), can be a suitable solution to retain phosphorus thanks to their low maintenance requirements and presumably long-term removal capacity (Molle et al, 2005;Molle et al, 2011).…”