Physicochemical properties related to long-term phosphorus retention by drinking-water treatment residuals.
Drinking-water treatment residuals (WTRs) are nonhazardous materials that can be obtained free-of-charge from drinking-water treatment plants to reduce soluble phosphorus (P) concentrations in poorly P sorbing soils. Phosphorus sorption capacities of WTRs can vary 1-2 orders of magnitude, on the basis of short-term equilibration times (up to 7 d), but studies dealing with long-term (weeks to months) P retention by WTRs are lacking. Properties that most affect long-term P sorption capacities are pertinent to the efficacy of WTRs as amendments to stabilize P in soils. This research addressed the long-term (up to 80 d) P sorption/desorption characteristics and kinetics for seven WTRs, including the influence of specific surface area (SSA), porosity, and total C content on the overall magnitude of P sorption by seven WTRs. The data confirm a strong but variable affinity for P by WTRs. Aluminum-based WTRs tended to have higher P sorption capacity than Fe-based WTRs. Phosphorus sorption with time was biphasic in nature for most samples and best fit to a second-order rate model. The P sorption rate dependency was strongly correlated with a hysteretic P desorption, consistent with kinetic limitations on P desorption from micropores. Oxalate-extractable Al + Fe concentrations of the WTRs did not effectively explain long-term (80 d) P sorption capacities of the WTRs. Micropore (CO2-based) SSAs were greater than BET-N2 SSAs for most WTRs, except those with the lowest (<80 g kg(-1)) total C content. There was a significant negative linear correlation between the total C content and the CO2/N2 SSA ratio. The data suggest that C in WTRs increases microporosity, but reduces P sorption per unit pore volume or surface area. Hence, variability in C content confounds direct relations among SSA, porosity, and P sorption. Total C, N2-based SSA, and CO2-based SSAs explained 82% of the variability in the long-term P sorption capacities of the WTRs. Prediction of long-term P sorption capacities for different WTRs may be achieved by taking into account the three proposed variables.
Environmental Geochemistry Laboratory, Department of Earth and Environmental Science, University of Texas, San Antonio, 6900 North Loop 1604, San Antonio, Texas 78249-0663, USA. Konstantinos.Makris@utsa.edu
Konstantinos C
KC
Makris
Willie G
WG
Harris
George A
GA
O'Connor
Thomas A
TA
Obreza
Herschel A
HA
Elliott
D000327:Adsorption; D000535:Aluminum / Q000032:analysis / Q000737:chemistry; D002244:Carbon / Q000032:analysis; D002245:Carbon Dioxide / Q000737:chemistry; D007501:Iron / Q000032:analysis / Q000737:chemistry; D007700:Kinetics; D009584:Nitrogen / Q000737:chemistry; D010070:Oxalates / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D016062:Porosity; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D014873:Water Pollutants / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D014881:Water Supply
D010070:Oxalates; D014873:Water Pollutants; D002245:Carbon Dioxide; D010758:Phosphorus; D002244:Carbon; D000535:Aluminum; D007501:Iron; D009584:Nitrogen