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Effect of chromium on granule-based anammox processes
Xiao-Yan Jiang1, Ya-Fei Cheng1, Wei-Qin Zhu1
1College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 310036, China; Key Laboratory of Hangzhou City for Ecosystem Protection and Restoration, Hangzhou Normal University, Hangzhou 310036, China.
Bioresource Technology
|March 31, 2018
Summary
This study assessed anaerobic ammonium oxidation (anammox) in chromium-contaminated wastewater. While high chromium concentrations inhibit anammox, long-term adaptation can enhance tolerance, showing potential for treating such industrial effluents.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Bioremediation of heavy metals
Background:
- Industrial wastewater often contains toxic heavy metals like chromium, posing challenges for biological treatment processes.
- Anaerobic ammonium oxidation (anammox) is an efficient nitrogen removal process, but its application in metal-contaminated streams is limited.
- Understanding the impact of chromium on anammox bacteria is crucial for developing effective treatment strategies.
Purpose of the Study:
- To evaluate the feasibility of applying the anammox process to treat wastewater contaminated with chromium.
- To determine the inhibitory effects of different chromium (VI) concentrations on anammox granule activity and performance.
- To investigate chromium removal mechanisms and the potential for anammox process adaptation to chromium toxicity.
Main Methods:
- Batch tests were conducted to assess anammox granule activity inhibition by varying Cr(VI) concentrations and pre-exposure times.
- Chromium adsorption onto extracellular polymeric substances (EPS) was quantified.
- Long-term operation of an up-flow anaerobic sludge blanket (UASB) reactor was performed to evaluate anammox performance under chromium stress.
- Nitrogen removal rate (NRR) and specific anammox granule activity were monitored.
Main Results:
- The 50% inhibition concentration (IC50) of Cr(VI) on anammox biomass was determined to be 296.5 mg/L.
- Over 93.9% of chromium was adsorbed by loosely and tightly bound EPS at Cr(VI) concentrations below 60 mg/L.
- In the UASB reactor, Cr(VI) concentrations as low as 2 mg/L significantly inhibited anammox performance, reducing NRR to 1.49 ± 0.89 kg N/m³d, compared to 11.37 ± 1.30 kg N/m³d in the control.
- Specific anammox granule activity decreased to 22% of initial levels under chromium stress.
Conclusions:
- The anammox process is sensitive to chromium contamination, with significant inhibition observed even at low Cr(VI) concentrations.
- Chromium removal is primarily mediated by adsorption onto bacterial EPS.
- Long-term exposure and adaptation can enhance the tolerance of the anammox process to Cr(VI), suggesting potential for its application in chromium-containing wastewater treatment with proper acclimatization.
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