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

Abstract

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.

Removal of Pathogens in Onsite Wastewater Treatment Systems: A Review of Design Considerations and Influencing Factors

“…More recently, hybrid OWTSs which comprise a CW or an infiltration percolation system with a subsequent filter or CW have been found to achieve higher pathogen removal efficiency compared to single-stage systems [41,44,137,156,166], because the hybrid system synergistically integrated the benefits of both types of CWs which created optimal hydraulic conditions and longer HRT [9]. For example, the highest removal rates of TC, FC, and FS from 97.7 to 99.4% were observed in hybrid systems, followed by subsurface flow CWs and free water surface CWs [167].…”

“…In recent years, biochar as an environmentally friendly sorbent has gained attention for contaminant removal in wastewaters [197]. It was considered as a suitable medium to improve pathogen removal due to its small pore size and large surface area [94,166,198].…”

Biochar application in biofiltration systems to remove nutrients, pathogens, and pharmaceutical and personal care products from wastewater

“…For example, in a biochar‐amended (33%, v/v) stormwater biofilter, an additional 0.5–1.0 log 10 E. coli removal was achieved at higher hydraulic loading compared with the control (sand only) system (sand pore water velocity 22.4–25.4 cm h −1 vs. biochar‐amended biofilter pore water velocity 20.0–21.7 cm h −1 ) (Kranner et al., 2019). On the other hand, the hydraulic loading rate increase (from 23 to 39 L m −2 d −1 ) did not affect E. coli removal (2.48–3.39 log 10 ) in the combined vertical–horizontal flow biochar filtration system (Dalahmeh et al., 2019).…”

Pharmaceutical and Antibiotic Pollutant Levels in Wastewater and the Waters of the Zarqa River, Jordan

“…All influent, effluent, and river water samples were extracted using solid-phase extraction with Oasis HLB cartridges (200 mg, 6 cc; Waters Corporation, Manchester, UK) according to the extractions method previously described in Dalahmeh et al [36], Dalahmeh et al [37], nd Gros et al [38]. Before extraction, the samples were spiked with 100 µL of IS mixture containing 1 ng µL −1 diclofenac 13 C 6 , hydrochlorothiazide 13 C 6 , carbamazepine 13 C 15 N, and ibuprofen-d 3 .…”