Laboratory evaluation of alum, ferric and ferrous-water treatment residuals for removing phosphorous from surface water

Abstract

Numerous drinking water plants and agricultural wastewaters generate water treatment residuals (WTR) during coagulation processes. These WTRs may be effective at reducing nutrients entering waterways, thereby decreasing the potential formation of algal blooms. Of the WTRs used in this study, Al-based WTR (Al-WTR) was the most effective achieving a 20 °C cumulative adsorbed concentrations (q e ) after 28 days of desorption of 63–76 mg PO 4 /kg Al-WTR depending on the initial spiked concentration. When the isotherm temperature was 5 °C, Al-WTR effectiveness decreased. Ferric chloride WTR (Fe-WTR) was only effective when 0.6 mg/L of PO 4 was spiked to surface water with 0.01 mg/PO 4 stored at 20 °C yielding a 28 day cumulative q e 5.67 mg PO4/kg Fe-WTR. At 5 °C, the cumulative q e after extended desorption was 1–4.63 mg/kg Fe-WTR. Ferrous sulfate based WTR (Fe2-WTR) was not capable of adsorbing any additional PO 4 regardless of the spiked concentration or temperature.

Correlation of Phosphorus Adsorption with Chemical Properties of Aluminum-Based Drinking Water Treatment Residuals Collected from Various Parts of the United States

“…The reaction was fast at the beginning, with most P removed from the solution in a matter of minutes. Ligand exchange is the dominant mechanism in this phase, whereas over an extended period, intraparticle diffusion plays a more dominant role in P removal, resulting in a second, slower phase [ 10 , 39 , 46 , 52 , 53 , 54 , 55 ]. The ligand exchange reaction is presented in Equation (6) [ 53 ], whereby the adsorption of H 2 PO 4 − on Al-WTRs is accompanied by the production of hydroxide ions, subsequently increasing the pH of the solution.…”

Application of modified water treatment residuals in water and wastewater treatment: A review

“…Among the different applications of WTRs, their use in the water and wastewater industries has received more attention. Different types of reuses have been suggested in water treatment, which include (a) recovering coagulants from WTRs and using them as coagulants in wastewater treatment, and (b) direct reuse of WTRs as adsorption/filtration medium in wastewater treatment [ [9] , [10] , [11] , [12] , [13] ]. While some of these are already applied on a field/pilot scale, some are still at the laboratory scale investigations.…”

Design and Preliminary Testing of an In-Field Passive Treatment System for Removing Phosphorus from Surface Water

“…Processing and handling WTRs often require a significant portion of water treatment plant operating expenses [10]. Researchers have found that WTRs can be used to adsorb reactive phosphorous (PO 4 3− ) which could lead to viable reuse of WTRs [11][12][13][14][15].…”