Initial Results of Using Biochar Derived from Spent Coffee Grounds to Remove Pollutants from Livestock Wastewater in Vietnam

Biochars derived from spent coffee grounds were pyrolysed at different temperatures and retention times, including CF1-CF4 samples (500 °C for 0.5, 1.5, 3, 6 h); CF5-CF8 samples (600 °C for 0.5, 1.5, 3, 6 h) and CF9-CF12 samples (700 °C for 0.5, 1.5, 3, 6 h). These biochars were examined to determine their ability to remove pollutants (COD, TSS, total N and total P) from livestock wastewater. The initial livestock wastewater was treated with 12 types of biochar with masses of 2, 4 and 6 g at reaction times from 1, 2, 4 to 8 h to assess the adsorption efficiency of the biochar. Adsorption efficiency for these pollutants increased with increasing reaction time and biochar mass. The combination of 8 h reaction time and 6 g biochar weight showed the highest adsorption efficiency. At an 8 h reaction time with 4 g biochar, only COD content was adsorbed by the CF4 biochar sample at a level meeting the output requirements according to the Vietnam standard QCVN 40:2011/MONRE national regulation for industrial wastewater; the remaining 11 treated wastewater samples retained pollutant concentrations that were 1.6 to 3.6 times higher than the acceptable values. The TSS content in all 12 samples met the standard limit value requirement. The total N content was 3.3 to 4.2 times higher (excepting the CF4 sample) and the total P content was 1.07 to 1.15 times higher (excepting the CF4, CF8, CF9 and CF11 samples) than the standard limit values. With 6 g biochar and 8 h reaction time, all four parameters adsorbed with 12 biochar samples were significantly reduced, producing water with concentrations lower than the required limit according to the QCVN 40:2011/MONRE regulation. The results showed that the biochar made from spent coffee grounds is a potential sorbent to remove pollutants from livestock waste water.