Precipitation of organic arsenic compounds and their degradation products during struvite formation.
Roxarsone (ROX) and arsanilic acid (ASA) have been extensively used as organoarsenic animal feed additives. Organic arsenic compounds and their degradation products, arsenate (As(V)) and arsenite (As(III)), exist in the effluent from anaerobic reactors treating animal manure contaminated by ROX or ASA with ammonium (NH4(+)-N) and phosphate (PO4(3-)-P) together. Therefore, arsenic species in the effluent might be involved in the struvite formation process. In this study, the involvement of organic arsenic compounds and their degradation products As(V) and As(III) in the struvite crystallization was investigated. The results demonstrated that arsenic compounds did not substantially affect the PO4(3-)-P recovery, but confirmed the precipitation of arsenic during struvite formation. The precipitation of arsenic compounds in struvite was considerably affected by a solution pH from 9.0 to 11.0. With an increase in pH, the content of ASA and ROX in the precipitation decreased, but the contents of As(III) and As(V) increased. In addition, the arsenic content of As(V) in the struvite was higher than that of As(III), ASA and ROX. The results indicated that the struvite could be contaminated when the solution contains arsenic species, but that could be minimized by controlling the solution pH and maintaining anaerobic conditions during struvite formation.
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Institute of Water Treatment and Wastes Reutilization, Hefei University of Technology, Hefei 230009, China.
Jin-Biao
JB
Lin
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Institute of Water Treatment and Wastes Reutilization, Hefei University of Technology, Hefei 230009, China.
Shoujun
S
Yuan
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Institute of Water Treatment and Wastes Reutilization, Hefei University of Technology, Hefei 230009, China. Electronic address: dwhit@126.com.
Wei
W
Wang
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Institute of Water Treatment and Wastes Reutilization, Hefei University of Technology, Hefei 230009, China. Electronic address: zhhu@hfut.edu.cn.
Zhen-Hu
ZH
Hu
Department of Chemistry, University of Science & Technology of China, Hefei 230026, China.
Han-Qing
HQ
Yu
Anaerobic digestion; Arsanilic acid; Inorganic arsenic; Roxarsone; Struvite