The efficiency of anaerobic biofilters (AnBF) as low-cost wastewater treatment systems was investigated. Miscanthus-biochar was used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal wastewater treatment plant was stored in a sedimentation tank for two days to allow pre-settlement of wastewater particles. Subsequently, wastewater was treated by AnBFs at 22 °C room temperature at a hydraulic loading rate of 0.05 m∙h⁻¹ with an empty bed contact time of 14.4 h and a mean organic loading rate of 509 ± 173 g_COD∙m⁻³∙d⁻¹. Mean removal of chemical oxygen demand (COD) of biochar filters was with 74 ± 18% significantly higher than of sand filters (61 ± 12%). In contrast to sand filters with a mean reduction of 1.18 ± 0.31 log-units, E. coli removal through biochar was with 1.35 ± 0.27 log-units significantly higher and increased with experimental time. Main removal took place within the schmutzdecke, a biologically active dirt layer that develops simultaneously on the surface of filter beds. Since the E. coli contamination of both filter materials was equal, the higher removal efficiency of biochar filters is probably a result of an improved biodegradation within deeper zones of the filter bed. Overall, performance of biochar filters was better or equal compared to sand and have thus demonstrated the suitability of Miscanthus-biochar as filter media for wastewater treatment.

Access to improved sanitation is often lacking in many low-income countries, and approximately 90% of the sewage is discharged without treatment into receiving water bodies. The aim of this study was the development and evaluation of an efficient low-cost wastewater treatment system for developing countries. Biochar and woodchips, potential locally available and inexpensive materials, were used for anaerobic wastewater filtration and their suitability evaluated in comparison to gravel as a common reference material. Filters were fed with raw sewage from a municipal full-scale wastewater treatment plant in Germany at 22 °C room temperature with a hydraulic loading rate (HLR) of 0.05 m∙h⁻¹. This resulted in a mean organic loading rate (OLR) of 252 g_COD∙m⁻³∙d⁻¹ and a mean organic surface load of 456 g_COD∙m⁻²∙d⁻¹. To determine the influence of different filter materials, the removal efficiency of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and faecal indicator bacteria (FIB) E. coli and enterococci were tested. It was found that COD (up to 90%), TOC (up to 80%), FIB (up to 1.7 log₁₀-units), and turbidity (effluent turbidity below 35 NTU) could be significantly reduced. The findings of this study demonstrate the potential of anaerobic filters (AFs) for wastewater treatment in low-income countries to reduce water pollution and comprehensively improve water quality. The performance of biochar filters was significantly better over the entire experiment compared to woodchip and gravel filters with respect to COD, TOC, turbidity, and FIB removal, indicating the superior properties of biochar for wastewater treatment.

Activated carbon (AC), used for removal of organic micropollutants in European wastewater treatment plants (WWTPs), is usually produced from non-renewable resources that need to be transported over long distances. Utilising local residual biomass as a raw material may be advantageous in terms of sustainability. This study investigated the environmental and energy balances of using biowaste and biomass from landscape management for micropollutant removal at a commercial scale WWTP. Both residual biomasses were processed using the integrated generation of solid fuel and biogas from biomass (IFBB) technique to obtain a press cake that was used as feedstock for AC production. The results showed a lower global warming potential (GWP) and cumulative energy demand in comparison to a fossil-based conventional AC Differences in GWP between residual and fossil ACs were enhanced when the end-of-life incineration step was considered, and residual AC had a lower social risk associated with its production. Energy efficiency of AC production was substantially increased by utilising waste heat generated in the pyrolysis process of biochar production and by using electricity generated in a combined heat and power plant using biogas from the methanation of IFBB press fluids. Converting residual biomass into activated carbon using IFBB and a state-of-the-art pyrolysis and activation unit along with energy recovery would improve WWTP sustainability and self-sufficiency in terms of the raw materials required.