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Bacteria and virus removal in denitrifying bioreactors: Effects of media type and age
- Source :
- Ecological Engineering. 138:46-53
- Publication Year :
- 2019
- Publisher :
- Elsevier BV, 2019.
-
Abstract
- Denitrifying bioreactors are simple, low-cost ecotechnologies designed to reduce nitrate (NO3−) present in septic tank effluent and drainage water. Recent studies indicate that, in addition to significant reduction in NO3− loads, these systems are also able to remove microbial contaminants from municipal wastewater. However, the removal of microbial contaminants in denitrifying bioreactors remains poorly characterised and factors that control removal in denitrifying bioreactors remain unexplored. In this study, the removal efficiency of faecal indicator bacteria Escherichia coli (E. coli) and total coliforms (TC) as a model for bacterial pathogens and F-specific RNA bacteriophage (FRNA bacteriophage) as a model for viruses was assessed for mesocosm-scale (∼700 L) bioreactors receiving municipal wastewater. Systems were filled with two different slow-release carbon sources: woodchip and coconut husk. The effect of media age on attenuation of microbial contaminants was assessed by comparing the performance of 8-year old systems with equivalent newly constructed woodchip and coconut husk bioreactors. Additionally, removal performance of these carbon substrates was compared to that of gravel, a non-carbon substrate commonly used in subsurface flow (SSF) constructed wetlands. Substantial reduction of E. coli, TC and FRNA bacteriophage from primary treated municipal wastewater was achieved in all bioreactors. Mean annual log10 removal efficiencies were similar between microbial indicators ranging from 1.4 to 1.9 for TC, 1.3 to 1.8 for E. coli and 1.3 to 2.0 for FRNA bacteriophage. All denitrifying bioreactors showed consistent year-round performance and long-term performance which did not markedly change in the ninth year of operation. The woodchip or coconut husk bioreactors achieved microbial effluent quality within the same range of log10 removal rates achieved in gravel-based systems. This suggests that denitrifying bioreactors, as well as reducing N loads, can effectively reduce microbial contaminants in wastewater, providing a complimentary disinfection role. Further research is needed to increase understanding of factors affecting removal of microbial contaminants in denitrifying bioreactors to support design of these systems for microbial contaminant removal.
- Subjects :
- Environmental Engineering
media_common.quotation_subject
Septic tank
010501 environmental sciences
Management, Monitoring, Policy and Law
01 natural sciences
Husk
chemistry.chemical_compound
Denitrifying bacteria
Nitrate
Bioreactor
Effluent
0105 earth and related environmental sciences
Nature and Landscape Conservation
media_common
biology
04 agricultural and veterinary sciences
equipment and supplies
Pulp and paper industry
biology.organism_classification
chemistry
Wastewater
040103 agronomy & agriculture
0401 agriculture, forestry, and fisheries
Environmental science
Bacteria
Subjects
Details
- ISSN :
- 09258574
- Volume :
- 138
- Database :
- OpenAIRE
- Journal :
- Ecological Engineering
- Accession number :
- edsair.doi...........4aedc6c1457f334edd75d6bc517c3639