Treatment of wine distillery wastewaters by high rate anaerobic digestion and submerged membrane systems

Melamane, Xolisa Lorraine (2007) Treatment of wine distillery wastewaters by high rate anaerobic digestion and submerged membrane systems. PhD thesis, Rhodes University.

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Abstract

Experiences in treating wine distillery wastewaters (WDWs) contribute to the field of oenology as many oenologists are concerned with the selection, efficiency and economy of their wastewaters. Wine distillery wastewaters are strongly acidic, have high chemical oxygen demand (COD), high polyphenol content and are highly variable. Primary attention was focussed on sustainable biological treatment of raw wine distillery wastewater (RWDW) and fungally pre-treated wine distillery wastewater (FTWDW) by energy-efficient high rate anaerobic digestion (AD). This study also explored the development of a novel dual-stage anaerobic digestion ultrafiltration (ADUF) process, using a ceramic submerged membrane bioreactor (SMBR) in the treatment of both RWDW and FTWDW. The first stage was for the selection of microorganisms that were able to treat the toxic pollutants from WDWs. It was operated at a high feed-to-microorganism ratio. The second stage, a secondary digester, was operated like a typical membrane bioreactor at a low feed-to-microorganism ratio to sustain a stable efficient population for a long period. The characteristics of RWDW were as follows: pH 3.83, 15 000 mg/l soluble COD (CODs) and 5229 mg/l of phenols. After pre-treatment of RWDW with Trametes pubescens, starting parameters for FTWDW were as follows: pH 6.7, 7000 mg/l soluble COD (CODS) and 1440 mg/l of phenols. During operation of a high rate anaerobic digester for RWDW treatment, K2HPO4 was required for buffering the digester. Volatile fatty acid concentrations were <300 mg/l throughout the study, indicating degradation of organic acids present. Mean CODS removal efficiency for the 130 day study was 87 %, while the mean polyphenol removal efficiency was 85 %. Addition of 50 mg/l Fe3+ increased the removal efficiencies of CODS to 97 % and of polyphenols to 99 %. High removal efficiencies of CODS and polyphenols were attributed to the addition of macronutrients and micronutrients that caused pH stability and stimulated microbial activity. The CODS removal efficiency of high rate anaerobic digestion of FTWDW reached 99.5%. During FTWDW digestion, pH buffering was achieved using K2HPO4. A combination of a SMBR and a secondary digester was tested for the treatment of RWDW and FTWDW during a 30 day study. Results for RWDW showed that pH buffering was achieved by dosing the feed stream with CaCO3 and K2HPO4. Buffering proved to be significant for optimum performance of the system in removal of soluble CODS, and volatile fatty acids (VFAs). Different batches of RWDW used for feeding the reactor had variable compositions with respect to concentrations of nitrates, ammonium and total phenolic compounds. Ammonium accumulated in the secondary digester after 14 days of system operation, indicated the time required for the establishment of anaerobic conditions in the system. Dosing of the SMBR treating FTWDW with CaCO3 and K2HPO4 buffered the pH;this proved significant for optimum performance of the system in removal of CODS. The system eliminated an average of 86 (± 4) % of CODS present in the FTWDW. The residual CODS levels in the effluent were approximately 400 mg/l, significantly lower than the concentrations observed when treating RWDW, indicating that fungal pre-treatment might have provided additional nutrients for removal of recalcitrant components of the wastewater. The resulting effluent was rich in nitrates and phosphates and might be used as a fertiliser. Alternatively, a membrane process, such as reverse osmosis (RO) or nanofiltration (NF) could be applied to raise the water quality to meet the levels required for reuse. Biomass samples were obtained from the four treatment systems and population shifts characterization using phospholipids fatty acids (PLFA) and 16S rRNA analysis to provide an indication of limitations within the microbial population. The values of the concentrations of the individual PLFAs detected in the samples indicated that ten bacterial species were present, with the GC content of the 16S rRNA increasing from 1 to 10. Analysis of denaturing gradient gel electrophoresis DGGE data indicated that the composition of the archeal community changed the consortia used for both RWDW and FTWDW treatment. Changes in band intensities indicated the presence of different components of the archeal communities. The results were not conclusive in terms of species identity as cloning, sequencing and phylogenetic analyses were not performed, but they did indicate microbial population shifts and species diversity for high rate anaerobic digestion. The results also confirmed prevalence of relatively few species during operation of SMBRs for treatment of RWDW and FTWDW, which suggested that the microorganisms that survived were either tolerant of toxic components of RWDW and FTWDW or they were able to remove polyphenols.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Oenology, Wine making, Distillary waste water, Sewage treatment, Membrane reactors, Bioreactors
Subjects:Q Science > QD Chemistry > QD241 Organic chemistry > QD415 Biochemistry
T Technology > TP Chemical technology > Biotechnology
Divisions:Faculty > Faculty of Science > Biochemistry, Microbiology & Biotechnology
ID Code:2753
Deposited By: Philip Clarke
Deposited On:04 May 2012 12:20
Last Modified:04 May 2012 12:20
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