ABSTRACT
Plant herbs specifically serai wangi (SW) and peppermint (PPM) are selected for its insect repellent properties as the use of chicken manure (CM) in anaerobic digestion (AD) potentially attract flies due to the digestate produced. Hence, the addition of SW and PPM in the AD system of CM could deter flies' infestation while producing biogas. Previous work has shown that AD of sawdust (SD) and CM with these plant herbs were able to produce biogas and reduce the flies attraction towards the digestate. However, the combination of SW and PPM for AD of CM has yet to be investigated. This work describes the effect of mixing SW and PPM on the co-AD of SDCM with respect to biogas production, methane yield and kinetic analysis. The mixture of SW and PPM was varied at different concentrations. The composition of methane in biogas was characterized every 10 days by using gas chromatography (GC) equipped with a thermal conductivity detector (TCD). The results suggest that co-AD of 10SW10PPM exhibited the highest biogas production (52.28 mL/gvs) and methane yield (30.89 mL/gvs), which the purity of methane increased by 18.52% as compared to SDCM. However, increasing the concentration of SW and PPM does not significantly improve the overall process. High R2 (0.927-0.999), low RMSE (0.08-0.61) and low prediction error (<10.00%) were displayed by the modified Gompertz, logistic and Cone models. In contrast, Monod and Fitzhugh model is not preferred for the co-AD of SDCM with a mixture of SW and PM, as a high prediction error is obtained throughout the study. Increasing the dosage of PPM decreases the maximum cumulative methane yield, ranging from 31.76 to 7.01 mL/gvs for modified Gompertz and 89.56 to 19.31 mL/gvs for logistic model. The Modified Gompertz obtained a lag phase of 10.01-28.28 days while the logistic model obtained a lag phase of 37.29-52.48 days.
ABSTRACT
Bittern contains a high ionic strength that can be used as an alternative coagulant in wastewater treatment. The magnesium content in the bittern could promote the removal of suspended particles and nutrients as settleable precipitates. This would create a more compact and manageable sludge. This study investigates the performance of bittern as a coagulant for fish market wastewater treatment. The effectiveness of bittern was evaluated based on the efficiency of pollutants removal and the amount of residual magnesium. The experiments were performed using a standard jar test. Response surface methodology (RSM) based on a two-factor central composite design (CCD) was used to design the experiment. The parameters involved were pH (7.5, 9, and 10.5) and coagulant dose (0.5, 1.5, 2.5 mL L-1). The maximum removal efficiencies (i.e., 93.3% TSS, 87.5% COD, 37.6% ammonium, and 91.3% phosphate) were recorded at pH 10.5 and 1.5 mL L-1 dose of bittern, while the optimum results (desirability value of 0.929) may occur at pH 10.5 and a dose of 1.284 mL L-1. Approximately 51% of struvite and 48% of calcite precipitates were identified in the generated sludge, which can possibly be used as supplementary material in agrochemical industry with further treatment.