Abstract
Contamination of water sources by inappropriately disposed poorly treated wastewater from countryside establishments is a worldwide challenge. This study tested the effectiveness of retrofitting sand (Sa)- and gas–concrete (GC)-packed reactors with biochar (C) in removing turbidity, dissolved organic carbon (DOC), phosphate (PO43−), and total phosphorus (Ptot) from wastewater. The down-flow reactors were each intermittently loaded with 0.063 L/d for 399 days. In general, all reactors achieved <3 NTU (Nephelometric Turbidity Units) effluent turbidity (99% efficiency). GC reactors dominated in inlet PO43− (6.1 mg/L) and DOC (25.3 mg/L) reduction, trapping >95% and >60%, respectively. Compared to Sa (PO43−: 35%, DOC: 52%), the fortified sand (SaC) filter attenuated more PO43− (>42%) and DOC (>58%). Student t-tests revealed that C significantly improved the Sa PO43− (p = 0.022) and DOC (p = 0.034) removal efficacy. From regression analysis, 53%, 81%, and 85% PO43− sorption variation in Sa, C, and SaC, respectively, were explained by variation in their effluent pH measures. Similarly, a strong linear correlation occurred between PO43− sorption efficiency and pH of fortified (r > 0.7) and reference (r = 0.6) GC filters thus suggesting chemisorption mechanisms. Therefore, whereby only sand may be available for treating septic tank effluents, fortifying it with biochar may be a possible measure to improve its efficacy.
Highlights
The septic system has proved to be feasible for sewage handling in remote and rural areas [1].even though widely used, research has shown that septic systems contribute largely to loading of nutrients [2], pathogens [3], and organic compounds [4] in surface and ground water sources
In an X-ray diffraction (XRD) study by Narayanan and Ramamurthy [32], both macro- (50 nm–50 μm) and micro- (
This study successfully tested the idea of fortification of sand filters with biochar on boosting its performance in treating septic tank effluents (STE)
Summary
The septic system has proved to be feasible for sewage handling in remote and rural areas [1].even though widely used, research has shown that septic systems contribute largely to loading of nutrients [2], pathogens [3], and organic compounds [4] in surface and ground water sources. The septic system has proved to be feasible for sewage handling in remote and rural areas [1]. Alternative effective technologies, with which the treatment facilities used in remote and rural areas (mostly septic systems) could be replaced or improved, are scarce. Dissolved organic carbon (DOC) and nutrients are common constituents of septic tank effluent (STE) which often escape treatment in soil treatment units (STU) and end up in nearby surface water bodies. Since these can pass through 0.45 μm pores, common coarse media, such as
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