Non-domestic wastewater treatment with fungal/bacterial consortium followed by Chlorella sp., and thermal conversion of the generated sludge

Abstract
Liquid waste from biological stains is considered non-domestic wastewater difficult to treat, generating high environmental impact. Therefore, the objective of this work was to carry out secondary and tertiary treatment of these effluents at a pilot scale, using a fungal/bacterial consortium followed by Chorella sp., for 15 days. In addition, to obtain an adsorbent material for Malachite Green dye removal, sludge generated in the plant and pine bark co-pyrolysis was performed. For microalgae isolation and selection of the Chlorophyceae class, Chlorococcales order, and Chorella sp. genus Winogradsky columns were employed. After 15 days of pilot plant treatment, removal percentages of 91 ± 2%, 90 ± 4% and 17 ± 2% were obtained for Colour Units, Chemical Oxygen Demand and Nitrates, respectively. Two types of class II biochar (BC500 and BC700) and one of class III (BC300) were produced. The highest value for Fixed carbon (FC) was obtained at 300 °C (27.3 ± 3%), decreasing as the temperature increased by 25.9 ± 5% and 24.8 ± 2%, for BC500 and BC700, respectively. Biochar yield was 62.1 ± 3%, 46.3 ± 4% and 31.6 ± 3% for BC300, BC500 and BC700, respectively. Finally, BC500 and BC700 biochar efficiently adsorbed Malachite Green obtaining qe values of 0.290 ± 0.032, 0.281 ± 0.015, 0.186 ± 0.009 and 0.191 ± 0.012 mg g−1 at pH values of 4.0 and 8.0 ± 0.2, respectively. Pseudo-second order model demonstrated a chemical adsorption took place, which was influenced by pH.