The remediation of MTE water by combined anaerobic digestion and chemical treatment

Mechanical thermal expression (MTE) is a developing process for the non-evaporative removal of water from low-rank coals prior to combustion. The water removed in this process contains both organic and inorganic components that would prevent its direct disposal to the environment. This study investigated the use of anaerobic digestion, in combination with ozonation and/or coagulation, to remediate MTE water. Under appropriate conditions the concentration of organic impurities, as determined by BOD, was reduced to be below guideline limits for release to surface waters. However, the electrical conductivity was increased to levels that would only permit its use for irrigation of salt tolerant plants with adequate drainage. Evidence of the effectiveness of remediation for organic carbon removal was also demonstrated by FTIR and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The latter revealed that the volatilizable organic components (aliphatic and aromatic hydrocarbons) were reduced by ∼95% by anaerobic treatment.