Arsenic accumulation and volatilization in a 260-day cultured upflow anaerobic sludge blanket (UASB) reactor

Abstract

Roxarsone has been extensively used as an organoarsenic feed additive. Part of supplemented roxarsone was discharged into wastewater. UASB reactor has been widely applied to treat high concentration of organics wastewater. However, there was little report about the arsenic accumulation from organoarsenic biotransformation in an UASB reactor. In this study, the accumulation and volatilization of arsenic in a 260-day cultured UASB reactor spiked with 13.2 mg/L roxarsone were investigated. In the anaerobic granular sludge (AGS), the total arsenic concentrations were 5,276.90 ± 366.12 mg/kg AGS at the bottom of anaerobic sludge bed and 10,661.92 ± 539.63 mg/kg AGS at the top of anaerobic sludge bed. Nearly 50% arsenic in the AGS was extracted under acidic conditions, and the main specie of the extracted arsenic was arsenite (As(III)). In the aqueous phases, roxarsone was rapidly transformed into 4-hydroxy-3-aminophenylarsonic acid (HAPA) and unknown organoarsenic, which was further converted to inorganic arsenic and monomethylarsenate (MMA(V)), in which As(III) was also the main species. Volatile arsenic from the reactor spiked with roxarsone was released at a rate of 134.93 ± 6.61 ng/d. Based on the mass balance analysis of arsenic, 23.40% of the influent arsenic was accumulated in the AGS and 0.002% was released in the form of volatile arsenic. The results from this study indicated that the operation of anaerobic digestion reactor treating organoarsenic-contaminated wastewater and the disposal of the residual AGS should be well managed.

Photodegradation of roxarsone in the aquatic environment: influencing factors, mechanisms, and artificial neural network modeling

“…Arsenic species were analyzed using high performance liquid chromatography -hydride generationatomic uorescence spectrometry (HPLC-HG-AFS). The arsenic species were rstly separated with a 250 × 4.1 mm anion-exchange column (PRP X-100, Hamilton, Switzerland) at 30.0 °C, and then reduced to arsenic hydride by the mixed solution of 20.00 g/L KBH 4 and 5.00 g/L KOH for detection (Tang et al, 2017). The mobile phase was 10 mM (NH 4 ) 2 HPO 4 solution (adjusted to pH 6.0 using 10% formic acid) at a ow rate of 1.0 mL/min.…”

Enhancing Roxarsone Degradation and In Situ Arsenic Immobilization Using a Sulfate-Mediated Bioelectrochemical System

“…Concentrations of total arsenic and individual arsenic species were determined by liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS, AFS-8200, Beijing Titan) following previously reported methods. , The detection limits for total arsenic, inorganic arsenic, and organoarsenicals were 0.01, 0.05, and 1.0 μM, respectively. Arsenic contained in the sludge was extracted using sequential extraction to determine the amount of adsorbed arsenic (As ads ) .…”

“…Currently, livestock manure/wastewater treatment occurs mostly through anaerobic bioprocesses . Under anaerobic conditions, while ROX is easily transformed to HAPA through the reduction of its nitro group to an amino group, HAPA is resistant to further degradation. − As HAPA is water-soluble, it is easily discharged into the natural environment with effluents from wastewater treatment plants. Once discharged, HAPA can eventually degrade into more toxic As­(III) through photocatalytic or microbial degradation in the natural environment, i.e., surface waters, threatening water quality and security.…”

Electrochemical Phosphorus Recovery from Anaerobically Digested Sludge: Improving Product Purity and Concentration

“…For example, a three-chamber electrochemical cell, divided by anion exchange membrane (AEM) and cation exchange membrane (CEM), can separate P into the anolyte and metal ions into the catholyte, and achieve a median P recovery efficiency of 65% . Meanwhile, over 95% of Al, Cu, Cd, Cr, Pb, and Ni were removed from sludges/sludge ash, leading to a high-purity P product. , Ion exchange membranes reject neutral organic contaminants, resulting in 90% removal of those compounds from the P recovery product. , While the existing research underscores the viability of such systems, a more comprehensive mass analysis is needed to include metalloid contaminants like arsenic, whose speciation can be similar to that of ortho-P. , …”