Effects of Long-Term Wastewater Application on Chemical Properties and Phosphorus Adsorption Capacity in Soils of a Wastewater Land Treatment System

Abstract

The buildup of phosphorus (P) in the soil is a major factor limiting the operating life of a wastewater land treatment system. In this study, we evaluated changes of chemical properties, P profiles, and adsorption isotherms in the soils of a Muskegon wastewater land treatment system, which has received wastewater for ∼30 years. It was found that the pH in the 15-cm topsoil increased from ∼5−6 in 1973 to ∼7.4−7.8 in 2003; a large amount of salt (e.g., Ca, Mg) in wastewater was adsorbed by the soil; the soil Al content (either exchangeable or oxalate extractable) decreased, while the oxalate-extractable Fe content remained at the same level. Ca-bound P accounted for ≥70% of the total P adsorbed in the soil. The soil P adsorption capacity increased and was positively correlated with the concentration of exchangeable Ca in the soil. A higher concentration of exchangeable Ca was found in the 15-cm topsoil, where a higher total organic carbon was present. More P was accumulated in the upper soil than in the deeper soil. The adsorption of Ca in wastewater by the soil may extend the life expectancy of the Muskegon land treatment system.

Muskegon Wastewater Land Treatment System: Fate and Transport of Phosphorus in Soils and Life Expectancy of the System

“…In addition, other soil properties were measured, such as soil pH [25], oxalate-extractable Al (Ox-Al), Fe (Ox-Fe), and P (Ox-P) [26,27], exchangeable Ca/Mg [19,20,28], total organic matter [29], and the CaCO 3 content of the soil samples [30]. Detailed information on procedures of analytical methods was reported in [19,20].…”

“…In this study, one composite soil sample was made for each depth increment by mixing the same quantity of the three sieved soil samples that were taken at the same depth. Detailed information on procedures of sampling and sample treatment in the laboratory were reported in [19,20].…”

Variations in Phosphorus Speciation in Pilot Scale Subsurface Flow Wetlands Constructed with Blast Furnace Slag and Gravel

“…Wetlands can satisfactorily remove phosphorus (P) on a short term basis, which is otherwise difficult to degrade by secondary treatment, especially biological treatment systems [1]. Substrate binding was believed to contribute to more than 80% of P removal in constructed wetlands (CW), via complex physical, chemical and microbial interactions [2,3].…”

Agricultural By-Products for Phosphorous Removal and Recovery from Water and Wastewater: A Green Technology

“…These processes can be classified as chemical methods (precipitation, crystallization, anion exchanger, and adsorption), biological methods (assimilation, enhanced biological phosphorus removal, land treatment system, constructed wetlands), and physical methods (microfiltration, reverse osmosis, electrodialysis, and magnetic separation) (Hu et al, 2005;Zhang et al 2007;Bhojappa 2009;Benyoucef and Amrani 2011). Of these methods, chemical precipitation and biological processes are most commonly used.…”