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.

A composite of MCM-41 silica with rice husk was modified with dithizone with the aid of microwave radiation. The modified composite was characterized by different techniques and utilized for preconcentration of Cu²⁺, Zn²⁺ and Pb²⁺ prior to determination by flame atomic absorption spectrometry (FAAS). The adsorption process is optimized to attain the maximum efficiency. The procedure presented satisfying uptake characteristics with maximum adsorption capacity of 142.7, 102.9 and 228.8 mg g⁻¹ towards Cu²⁺, Zn²⁺ and Pb²⁺, respectively. The calibration graphs were linear up to 400 μg L⁻¹ for Cu²⁺ and Zn²⁺ and up to 800 μg L⁻¹ for Pb²⁺ with preconcentration factor of 240. The limits of detection were 0.28, 0.21 and 0.48 μg L⁻¹ for Cu²⁺, Zn²⁺ and Pb²⁺, respectively. The optimized procedure was utilized for the preconcentration of Cu²⁺, Zn²⁺ and Pb²⁺ in water and food samples prior to determination by FAAS with accepted precision and accuracy.