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Effect of Calcium on Moving‐Bed Biofilm Reactor Biofilms
Author(s) -
Goode C.,
Allen D. G.
Publication year - 2011
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143010x12780288628255
Subject(s) - biofilm , extracellular polymeric substance , calcium , chemistry , effluent , calcium alginate , settling , microbiology and biotechnology , biomass (ecology) , chemical oxygen demand , wastewater , environmental chemistry , chromatography , bacteria , environmental engineering , biology , ecology , environmental science , genetics , organic chemistry
The effect of calcium concentration on the biofilm structure, microbiology, and treatment performance was evaluated in a moving‐bed biofilm reactor. Three experiments were conducted in replicate laboratory‐scale reactors to determine if wastewater calcium is an important variable for the design and optimization of these reactors. Biofilm structural properties, such as thickness, oxygen microprofiles, and the composition of extracellular polymeric substances (EPS) were affected by increasing calcium concentrations. Above a threshold concentration of calcium between 1 and 50 mg/L, biofilms became thicker and denser, with a shift toward increasingly proteinaceous EPS at higher calcium concentrations up to 200 mgCa 2+ /L. At 300 mgCa 2+ /L, biofilms were found to become primarily composed of inorganic calcium precipitates. Microbiology was assessed through microscopy, denaturing grade gel electrophoresis, and enumeration of higher organisms. Higher calcium concentrations were found to change the bacterial community and promote the abundant growth of filamentous organisms and various protazoa and metazoan populations. The chemical oxygen demand removal efficiency was improved for reactors at calcium concentrations of 50 mg/L and above. Reactor effluents for the lowest calcium concentration (1 mgCa 2+ /L) were found to be turbid (>50 NTU), as a result of the detachment of small and poorly settling planktonic biomass, whereas higher concentrations promoted settling of the suspended phase. In general, calcium was found to be an important variable causing significant changes in biofilm structure and reactor function.