Evaluation of sludge biochar for removal of PPCPs in treated greywater

Abstract

Contaminants of emerging concern, including pharmaceuticals and personal care products (PPCPs), are detected in already vulnerable freshwater sources all over the world and lack of sufficient wastewater treatment and sludge management are the main pathways for PPCPs to enter the environment. Reuse of water could be necessary to cover the water demand in the future. The aim with this study is to evaluate a sludge biochar, pyrolyzed at 600°C, as a polishing step for PPCPs removal in treated greywater. Sludge is an on-site available feedstock for production of biochar for water treatment purposes and can contribute to a safe sewage sludge management. Activated carbon was used to compare the performance of the sludge biochar in a 16-day sorption column experiment. Greywater from a student housing at NMBU was treated with BAF reactor before spiked with the five selected PPCPs; Acetaminophen, Carbamazepine, N,N-Diethyl-meta-toluamide (DEET), Diclofenac and Octocrylene, to a concentration of 1 mg/L. Greywater quality after BAF treatment was exciding the limits for reuse of greywater suggested by IWA and EU, but was within the limits after polishing-step with biochar or activated carbon. The removal rates from the biochar and activated carbon effluents were > 90% for TSS, turbidity, BOD5 and CODT, and ≥80% for total phosphorus and total nitrogen. pH was unchanged in the biochar column effluents, while pH was increased in the activated carbon column effluents from day 1 to 10.

LC-MS/MS was used to measure PPCPs concentrations. Acetaminophen, carbamazepine, and diclofenac were removed with more than 99% by the biochar and activated carbon. Octocrylene was removed with more than 93% on day 1 to 10 and 80% on day 16. The sorption materials were not saturated at the end of the experiment, and sorption capacity of the biochar and activated carbon material could therefore not be calculated. The PPCPs loadings on the activated carbon and biochar in each column, were in average 0.26 mg PPCP/g activated carbon and 0.17 mg PPCP/g biochar. The evaluation of the sorption mechanisms of PPCPs onto biochar and activated carbon were based on the properties of the sorption materials and the PPCPs. ICP-MS/MS was used to decide heavy metal (As, Cd, Cr, Cu, Ni, Pb and Zn) concentrations in the column effluents. The results showed little or no leach from the biochar and the activated carbon material and some sorption of Ni and Zn were observed.