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Abstract
This paper investigated the accumulation of arsenic and its chemical fraction distributions in a low-sludge wastewater treatment system using “sonication-cryptic growth” method. Subsequent bio-reactors (SBR) were used; one SBR without sonication was used for control. Results showed that “sonication-cryptic growth” technique cut sludge production in SBR by 50%. The accumulation of arsenic in sludge occurred in both reactors; the accumulation was low in 0–60 days and showed a sharp increase in 60–90 days. The final sludge arsenic content in the low-sludge system was 1.23 times of that in the control system. However, the higher arsenic content in the low-sludge treatment system did not impact the COD removal and the sludge bioactivity. The low-sludge system had higher COD removal efficiency and higher sludge activity than those of the control. Further analyses of the chemical fraction distribution of arsenic showed that arsenic existed in different forms in the two systems. In the control system, the major form of arsenic in sludge was the organically bound fraction during 0–60 days, and the chemical fractions were redistributed during 60–90 days and the Fe/Mn oxide fraction and organically bound fraction were the main fractions. In the low-sludge system, the major form of arsenic in sludge was Fe/Mn oxides bound fraction during the whole operation duration.
Acknowledgments
Authors thank the financial supports from the National Natural Science Foundation of China (51278489), Program of International Sci. & Tech. Cooperation (MOST, 2010DFA92090), and Shenzhen Science Development Fund (JSF201006300042A).