Epsilon Archive for Student Projects

Abstract

This study investigated the performance of the biochar filter for wastewater treatment in on-site systems using two experiments; (1) Lab-scale pyrolysis for biochar production and adsorption experiment for evaluating the removability of phosphate and ammonium (2) Pilot-scale of multi-module biochar filter system to assess the removal of organic matter, phosphorus, nitrogen, and bacteria. Seven kinds of biomass (Date kernels, Olive kernels, Pistachio shells, Bark, Pine bark, Reeds, and Sludge) were pyrolyzed at 600 °C, their yield was measured, and their adsorption capacity on P and N was assessed. The lab-scale pyrolysis revealed the highest mass yield for sludge (35.4% on average), although it had the lowest carbon ratio (4.9%). The lowest mass yield was the reeds sample (5.56% on average). The carbon ratio of reeds and other biochar was 58.2-89.7% and the highest in pistachio biochar. The phosphate adsorption capacity was relatively high by pine bark biochar (0.50-0.75 mg-PO4 g-1 biochar), containing several metal ions. Ammonium was adsorbed at the highest in pistachio shell biochar (0.79-0.97 mg-NH4 g-1 biochar). For the pilot-scale multi-module filter setup, different sizes of commercial biochar (mixed softwood) were used. The filter was designed with six modules to treat organic materials, nitrogen, phosphorus, and bacteria. The pilot-scale biochar filter was operated over 60 days, and it worked well for most of the analyzed pollutants. Organic matter was well removed in terms of BOD and COD reduction; 92.5% (82.9-97.3%) and 82.81% (77.7-89.9%). Ammonium-nitrogen was nearly 100% transformed to nitrate by nitrification, but the reduction of total nitrogen to nitrogen gas was intermediate, about 40% on average. The result of phosphorus removal was not consistent due to the previous operation effect, and a longer-term operation would give a better result. The biochar filter worked well to reduce analyzed bacteria, which were E coli and Enterococcus spp. The average reduction rate of E coli was 3.57 log10 units, while Enterococcus spp. was 2.75 log10 units. It is significantly higher than the conventional on-site wastewater treatment by septic tank with soil drainage field (0.75-1.86 log10 units of fecal coliform). In summary, the biochar filter has a high potential to be an alternative treatment system. Further research for enhancing phosphorus removal and denitrification needs to be considered. The reference data of batch adsorption experiments using the commercial biochar is also needed.