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Title: Start-up of high anaerobic reactors treating dairy waste water
Author: Motta Marques, David Manuel Lelinho da
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1991
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The fundamental aspects of the biochemistry and microbiology of the anaerobic bacteria involved in the degradation of organic wastewaters to methane, as well as the application and limitation of anaerobic systems in the treatment of industrial organic waste streams has been reviewed, with emphasis on the start-up process of high rate type systems. In order to study the start-up of anaerobic fluidised bed (AFBS) and upflow anaerobic filter (AF) systems treating ice-cream factory wastewater, several start-up protocols were tested. The start-up·of AFB systems was investigated by applying different protocols while the organic load was increased stepwise. These protocols were: biological preconditioning of the wastewater in a continuous flow-stirred tank reactor, either with (1) constant or (2) variable hydraulic retention time; chemical preconditioning of the support medium by the addition of Ca(OH)2 (3), and of the wastewater with the supplementation of CaCl2 (4) and a mixture of detergents (5); conditioning of the support medium surface with biological polymer extracted from anaerobically digested sludge (6); and conditioning of the seed material with coenzyme M (7). The protocols for the AFBS enhanced the start-up performance, except the support medium conditioning with biopolymer. Each protocol increased the maximum efficiency of COD removal by comparison with the control system, although the best substrate removal efficiency was not associated with the best methane yield. Biological preconditioning of the wastewater at constant volume promoted a COD removal efficiency only slightly better in comparison with CoM and detergent amendment protocols (95. 92 and 93 %, respectively). Methane yields for the same systems were 0.157, 0.182 and 0.188 m3 C}4 kg-1 CODr. The start-up of the AF was carried out by applying stepped organic load increases, associated with the following protocol: precoating of the support medium with biological polymer. The AF appeared well suited to the treatment of ice-cream production wastewater with mean COD removal efficiencies of 81 % and methane yield of 0.270.m3 CH4 kg·l CODr, However, the precoating of polymer did not enhance the start-up process. The stability of AFBS and AF systems started-up under the different protocols was assessed by applying transient shocks of organic load, temperature and pH. Five and six fold increases in OLR were well tolerated in both types of system. Most of the overload substrate bypassed the systems, although mean increases of five fold in biogas production rate were observed. Recovery in terms of effluent COD took more than 24 hours for the AFBS and 72 hours for the AF. System temperature decreases to room temperature were well tolerated; biogas production rate was substantially reduced, although the COD removal efficiency was only reduced by 10 %. Severe damage to the systems was induced by the pH shock: increased greenish effluent suspended solids in both types of system was found, as well as re-suspended biomass, which was associated with impaired COD removal efficiency. An irreversible shift in COD removal efficiency occurred in the AF, with increasing volatile fatty acids (VFA) concentration. The changes in VFA concentrations in the AFBS system were less severe. The IA/PA ratio was able to reflect operational performance and transient instability. However, there is a threshold concentration of 100 mg TVFA 1-1 before the ratio indicates any alteration. For AFBS transients, total alkalinity was found to be a much better parameter of response.
Supervisor: Lester, John N. ; Cayless, Sandra M. ; de Luca, Sergio J. Sponsor: Conselho Nacional de Desenvolvimento Científico e Tecnológico ; Universidade Federal do Rio Grande do Sul ; British Council ; Science and Engineering Research Council ; Unilever Research ; Birds Eye Walls Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available