Phosphorus adsorption characteristics of a constructed wetland soil receiving dairy farm wastewater

Abstract

. 2002. Phosphorus adsorption characteristics of a constructed wetland soil receiving dairy farm wastewater. Can. J. Soil Sci. 82: 97-104. Adsorption to soil has been identified as a key wastewater P removal mechanism in treatment wetlands. Batch incubation experiments were performed to measure the capacity of a constructed dairy farm wetland in Pictou County, Nova Scotia, to remove P from solution. The constructed wetland had been receiving wastewater since 1996. Non-linear regression analysis was performed using the Langmuir adsorption model to describe the P adsorption characteristics for the wetland soil under study. The Langmuir model was adequate in describing the P adsorption characteristics of the system studied. The P adsorption maxima found were approximately 925, 924, and 1600 mg P kg -1 soil, for the deep zone soil, shallow zone soil, and a background soil (not receiving wastewater), respectively. The P adsorption maxima for the deep zone and shallow zone soils were not significantly different (P > 0.05) from one another, but were significantly lower (P < 0.05) than the background soil. These data, together with information on wastewater inflow and P loading, were used to predict a lifespan of 8 yr for this wetland, relative to P removal.Key words: Phosphorus, wetlands, constructed, adsorption, Langmuir, saturation Jamieson, T. S., Stratton, G. W., Gordon, R. et Madani, A. 2002. Adsorption du phosphore par une terre humide artificielle recevant les eaux usées d'une exploitation laitière. Can. J. Soil Sci. 82: 97-104. Un des principaux moyens pour extraire le phosphore (P) des eaux usées dans le traitement des terres humides est l'adsorption par le sol. Les auteurs ont recouru à l'incubation en lot pour jauger la capacité d'une terre humide artificielle à retirer le P dissous. La terre humide en question accueille les eaux usées d'une exploitation laitière du comté de Pictou, en Nouvelle-Écosse, depuis 1996. On a appliqué l'analyse par régression non linéaire au modèle d'adsorption de Langmuir pour préciser les propriétés du sol à l'étude. Le modèle de Langmuir décrit bien le mécanisme d'adsorption du système examiné. La quantité maximale de P adsorbée s'établit respectivement autour de 925, de 924 et de 1 600 mg par kg de sol pour la couche profonde, la couche superficielle et le sol témoin (ne recevant pas les eaux usées). La quantité maximale de P adsorbée ne diffère pas sensiblement (P > 0,05) entre la couche profonde et la couche superficielle, mais elle varie sensiblement de celle relevée dans le sol témoin (P < 0,05). Selon ces résultats et d'après les données sur l'apport d'eaux usées et la charge de P, les chercheurs estiment que la terre humide à l'étude parviendra à saturation au bout de huit ans.

A vertical flow constructed wetland for the treatment of winery process water and domestic sewage in Ontario, Canada: Six years of performance data

“…During the first two years of operation all TP concentrations were consistently below detectable levels in the effluent water; however, from 2010 to 2013 the effluent concentrations of TP were almost always above zero (Table 3). TP removal efficiencies were higher initially but because the main mechanism of TP removal in CWs is adsorption (Jamieson et al, 2002;Wood et al, 2008) the removal eventually began to decrease as adsorptions sites were filled. If TP removal efficiencies continue to decrease additional treatment steps may need to be taken or the adsorption sites could be refreshed with the removal and addition of clean gravel and sand.…”

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

“…Research on CWs with standard substrates (soil and/or gravel) shows that temporary P treatment can be possible, but it can fluctuate significantly depending on the hydrology of the system [24,53]; however, eventually adsorption sites become saturated and treatment performance decreases [54]. A comprehensive assessment of a 4-cell SF system at a 30-head dairy farm considered the P adsorption capacity of the wetland soils [20,53,54].…”

“…Research on CWs with standard substrates (soil and/or gravel) shows that temporary P treatment can be possible, but it can fluctuate significantly depending on the hydrology of the system [24,53]; however, eventually adsorption sites become saturated and treatment performance decreases [54]. A comprehensive assessment of a 4-cell SF system at a 30-head dairy farm considered the P adsorption capacity of the wetland soils [20,53,54]. Initially, the wetland proved capable of P removal (~86% concentration reduction; Table 2), but, over time, the P adsorption capacity decreased, and the wetland's lifespan with respect to P management was estimated to be eight years [20,54].…”

“…A comprehensive assessment of a 4-cell SF system at a 30-head dairy farm considered the P adsorption capacity of the wetland soils [20,53,54]. Initially, the wetland proved capable of P removal (~86% concentration reduction; Table 2), but, over time, the P adsorption capacity decreased, and the wetland's lifespan with respect to P management was estimated to be eight years [20,54].…”

“…Although some of the systems appeared to be rather successful at removing P (i.e., CRs > 80%; Table 2), the age of the wetland must be taken into account. Phosphorus removal will often be higher in the first few years of operation with decreases over time as the soil adsorption sites become saturated [54]. In six years of monitoring a study, [35] reported that TP removal decreased with time and recommended that additional TP treatment may be necessary.…”