Combined Vertical-Horizontal Flow Biochar Filter for Onsite Wastewater Treatment—Removal of Organic Matter, Nitrogen and Pathogens

This study investigated the performance of a combined vertical-horizontal flow biochar filter (VFF-HFF) system in terms of organic matter, total nitrogen (Tot-N), Escherichia coli and Salmonella removal and explored the effects of hydraulic loading rate (HLR) on pollutant removal. The combined VFF-H...

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Bibliographic Details
Published in:Applied sciences 2019-12, Vol.9 (24), p.5386
Main Authors: Dalahmeh, Sahar S, Assayed, Almoayied, Stenström, Ylva
Format: Article
Language:English
Subjects:
Advection
Anaerobic conditions
Anaerobic processes
Biofilms
Carbon
Charcoal
Chemical oxygen demand
Climate change
Denitrification
Drinking water
Efficiency
Effluents
Escherichia coli
Filtered wastewater
Flow
Hydraulic loading
Hydraulics
Load distribution
Loading rate
Nitrification
Nitrogen
Nitrogen removal
Organic matter
Particle size
Pathogens
Pollutant removal
Pollutants
Salmonella
Scanning electron microscopy
Vattenbehandling
Vertical flow
Wastewater treatment
Water purification
Water Treatment
Wetlands
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Summary:This study investigated the performance of a combined vertical-horizontal flow biochar filter (VFF-HFF) system in terms of organic matter, total nitrogen (Tot-N), Escherichia coli and Salmonella removal and explored the effects of hydraulic loading rate (HLR) on pollutant removal. The combined VFF-HFF system used biochar as the filter medium and comprised two stacked sections: (i) an aerobic vertical flow filter (VFF) in which the wastewater percolated through the biochar medium in unsaturated mode and (ii) a horizontal flow filter (HFF), in which the biochar was saturated with water and had limited access to air, to enable anaerobic conditions and enhance the denitrification process. The system was tested over 126 weeks using real wastewater applied at different HLR (23, 31, 39 L m−2 day−1). The results showed that long-term removal of organic matter in the entire system was 93 ± 3%, with most (87 ± 5%) occurring in the VFF. For Tot-N, the long-term removal was 71 ± 12%, with increasing trends for nitrification in the VFF and denitrification in the HFF. Mean long-term nitrification efficiency in the VFF was 65 ± 15% and mean long-term denitrification efficiency in the HFF 49 ± 14%. Increasing HLR from 23 to 31 L m−2 day−1 increased the nitrification efficiency from 42 to 61%. Increasing the HLR further to 39 L m−2 day−1 decreased the denitrification efficiency from 45 to 25%. HLR had no significant effects on VFF and HFF performance in terms of E. coli and Salmonella removal, although the VFF achieved a 1.09–2.1 log10 unit reduction and the HFF achieved a 2.48–3.39 log10 unit reduction. Thus, long-term performance, i.e., removal of pollutants measured during the last 52 weeks of the experiment, was satisfactory in terms of organic matter and nitrogen removal, with no signs of clogging, indicating good robustness of the combined VFF-HFF biochar filter system.
ISSN:2076-3417
2076-3417
DOI:10.3390/app9245386