Anaerobic co-digestion of coffee waste and sewage sludge

Centro de Engenharia Biológica, Universidade do Minho, 4710-057 Braga, Portugal.
Waste Management (Impact Factor: 3.22). 02/2006; 26(2):176-81. DOI: 10.1016/j.wasman.2004.12.022
Source: PubMed


The feasibility of the anaerobic co-digestion of coffee solid waste and sewage sludge was assessed. Five different solid wastes with different chemical properties were studied in mesophilic batch assays, providing basic data on the methane production, reduction of total and volatile solids and hydrolysis rate constant. Most of the wastes had a methane yield of 0.24-0.28 m3 CH4(STP)/kg VS(initial) and 76-89% of the theoretical methane yield was achieved. Reduction of 50-73% in total solids and 75-80% in volatile solids were obtained and the hydrolysis rate constants were in the range of 0.035-0.063 d(-1). One of the solid wastes, composed of 100% barley, achieved a methane yield of 0.02 m3 CH4(STP)/kg VS(initial), reductions of 31% in total solids, 40% in volatile solids and achieved only 11% of the theoretical methane yield. However, this waste presented the highest hydrolysis rate constant. Considering all the wastes, an inverse linear correlation was obtained between methane yield and the hydrolysis rate constant, suggesting that hydrolysis was not the limiting factor in the anaerobic biodegradability of this type of waste.

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Available from: Madalena S Alves, Dec 21, 2014
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    • "The anaerobically digested MDW still has high remnant COD (1e2 g/L) and dark color mainly consisting of melanoidins and related compounds which make its disposal problematic. This necessitates some further treatment prior to its disposal (Neves et al., 2006; Pant and Adholeya, 2007; Ria~ no et al., 2014). The low biodegradability and dark color of the remnant COD after anaerobic digestion is caused by organic recalcitrants (Mohana et al., 2007). "
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    ABSTRACT: Anaerobic digestion is used to treat effluents with a lot of organics, such as molasses distillery wastewater (MDW) which is the effluent of bioethanol production from molasses. The raw MDW requires a lot of dilution water before biodigestion, while the digested MDW has high level of recalcitrants which are problematic for its discharge. This study investigated ferric coagulation, Fenton, Fenton-like (with ferric ions as catalyst) processes and their combinations on the biodegradability of digested MDW. The Fenton and Fenton-like processes after coagulation increased the MDW biodegradability defined by (BOD5/COD) from 0.07 to (0.4-0.6) and saved 50% of H2O2 consumed in the classic Fenton process. The effluent from coagulation coupled to a Fenton-like process was used as dilution water for the raw MDW before the anaerobic digestion. The process was stable with volumetric loading of approx. 2.7 g COD/L/d. It resulted in increased overall biogas recovery and significantly decreased the demand for the dilution water.
    Full-text · Article · Mar 2016 · Journal of Environmental Management
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    • "The treatment of coffee extraction effluent is not only important to the primary producers but also to the other countries which import bulks of semi-processed coffee for further processing. Melanoidin has been reported as the main pollutant in the coffee industry effluents [5] [6]. In addition to causing dark color and high remnant COD, melanoidin in coffee has been reported to cause microbial inhibition [7] and may be responsible for the low biodegradability of the effluent. "
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    ABSTRACT: Melanoidin-rich industrial effluents, e.g. from coffee extraction plants and molasses distilleries, can cause potential environmental problems due to the high content of remnant dissolved organic carbon and dark color. It mainly consists of melanoidins and other organic colorants, which are recalcitrant to biological treatment. The current study was aimed to develop a polishing step after anaerobic digestion for the colorant elimination from melanoidin-rich wastewater (molasses distillery wastewater, MDW) using natural manganese oxides. Anaerobically digested MDW was used to test the removal of organic contents and color at different pH values. It was observed that the kinetics of colorant elimination was best described by the second order equation, with a significant dependence on pH. Furthermore, the liquid chromatography with organic carbon detection was applied to analyze the changes in molecular composition during the reaction. There was a preferential removal of low weight melanoidin molecules over higher weight molecules.
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    • "because even the countries that are not primary producers buy semi-produced coffee from which they process instant coffee. The major source of pollutant in the coffee industry effluent has been reported to be melanoidin, which causes dark colour and high remnant chemical oxygen demand (COD).[6] [7] Melanoidin from coffee has been reported to cause microbial inhibition [8] and may be responsible for low biodegradability of the effluent. "
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    ABSTRACT: Melanoidins are dark colored recalcitrant pollutants found in many industrial wastewaters including coffee manufacturing effluent, molasses distillery wastewater (MDWW), and other wastewater with molasses as raw material. The wastewaters are mostly treated with anaerobic digestion after some dilution to minimize the inhibition effect. However the dark color and recalcitrant dissolved organic carbon (DOC) mainly caused by melanoidin are not effectively removed. The aim of this study was to investigate the removal of color and remnant DOC by different coagulants from anaerobically digested MDWW. From the six coagulants tested, ferric chloride had the highest melanoidin (48%), color (92.7%) and DOC (63.3%) removal at pH 5 and a dosage of 1.6 g/l. Both polymer and inorganic salts coagulants tested had optimal color, melanoidin and DOC removal at acidic pH. The molecular size distribution of synthetic melanoidins by LC-OCD indicated a preferential removal of high-molecular-weight melanoidins over low weight melanoidins by the coagulation. Further studies should focus on how to improve biodegradability of the treated effluent for it to be reused as dilution water for anaerobic digestion.
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