Qualitative determination and application of sewage sludge and municipal solid waste compost for BTEX removal from groundwater

This work presents the efficiency of organic materials, such as compost (fresh and mature) from municipal solid waste and sewage sludge (untreated and digested), from the Wastewater Treatment Plant of Chania Prefecture, Crete in the degradation of petroleum hydrocarbons present in groundwater. In this study, all samples were characterized for various contents such as heavy metals, organic compounds, toxicity, phytotoxicity and bacteria population. Mature compost was the least phytotoxic obtaining a Germination Index of up to 95%, in two of the studied seeds, whereas digested sludge exhibited the highest phytotoxicity, with a Germination Index ranging from 0 to 15% for three types of seeds. Additionally, compost samples demonstrated higher bacteria content (107 CFUs/dry sample) than sludge (106 CFUs/dry sample). A series of batch experiments were conducted in order to determine the optimal operating conditions for sorption processes. Mixtures of BTEX (10 ppm) and solid samples (compost/sludge), in a ratio of 1:10 (w/w), were studied. Gas Chromatography–Mass Spectrometry analysis was used for the evaluation of BTEX removal rate via the reduction of BTEX concentration. According to the results, mature compost appeared to be the best adsorbent for BTEX, obtaining a maximum removal percentage of up to 90%. Equilibrium was reached within 12 h, for compost samples and within 24 h for sludges.