On-farm wastewater treatment using biochar from local agroresidues reduces pathogens from irrigation water for safer food production in developing countries

• Published in: The Science of the total environment 2019-09, Vol.682, p.601-610
• Main Authors: Kaetzl, Korbinian, Lübken, Manfred, Uzun, Gülkader, Gehring, Tito, Nettmann, Edith, Stenchly, Kathrin, Wichern, Marc
• Format: Article
• Language: English
• Subjects: (Rice husk) biochar; Agricultural residues; Anaerobic wastewater filtration; Fecal indicator bacteria; Low-cost biofiltration; Water reuse
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.05.142

In this study, the suitability of an anaerobic biofilter (AnBF) as an efficient and low-cost wastewater treatment for safer irrigation water production for Sub-Saharan Africa was investigated. To determine the influence of different ubiquitous available materials on the treatment efficiency of the AnBF, rice husks and their pyrolysed equivalent, rice husk biochar, were used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal full-scale wastewater treatment plant pretreated with an anaerobic filter (AF) was used in this experiment. The filters were operated at 22 °C room temperature with a hydraulic loading rate of 0.05 m·h−1 for 400 days. The mean organic loading rate (OLR) of the AF was 194 ± 74 and 63 ± 16 gCOD·m−3·d−1 for the AnBF. Fecal indicator bacteria (FIB) (up to 3.9 log10-units), bacteriophages (up to 2.7 log10-units), chemical oxygen demand (COD) (up to 94%) and turbidity (up to 97%) could be significantly reduced. Additionally, the essential plant nutrients nitrogen and phosphorous were not significantly affected by the water treatment. Overall, the performance of the biochar filters was significantly better than or equal to the sand and rice husk filters. By using the treated wastewater for irrigating lettuce plants in a pot experiment, the contamination with FIB was >2.5 log-units lower (for most of the plants below the detection limit of 5.6 MPN per gram fresh weight) than for plants irrigated with raw wastewater. Respective soil samples were minimally contaminated and nearly in the same range as that of tap water. [Display omitted] •Up to 3.9 log-units of fecal indicator bacteria could be removed from raw sewage.•Chemical oxygen demand was reduced by up to 94%.•Rice husk biochar achieved the most promising results from investigated materials.•FIB were reduced to a suitable level for irrigation following WHO guidelines.•Treated irrigation water reduced pathogen contamination on lettuce and in soil.