Anaerobic digestion application in the treatment of gelatin-manufacturing effluent

Lloyd, Magaretha Hester (2000-12)

Thesis (MSc)--Stellenbosch University, 2000.

Thesis

ENGLISH ABSTRACT: A severely polluted industrial effluent is generated by the local gelatinmanufacturing industry. Due to increasingly stringent restrictions on discharge qualities enforced by the National Water Act of 1998 and National Environmental Management Act of 1998, as well as increasing trade-effluent charges implemented via the Local Municipal Bylaws, the industry is compelled to consider a system to pre-treat the polluted effluent. A study was undertaken to examine the viability of anaerobic treatment of the gelatin-manufacturing effluent, since the anaerobic digestion technology is well recognised for the high success rate in the treatment of high-strength, complex wastewaters. Various laboratory and pilot-scale studies were done, using different hybrid Upflow Anaerobic Sludge Blanket (UASB) and contact designs. Two mesophilic laboratory-scale hybrid UASB digester designs, fitted with polyethylene (AD-1) and polyurethane (AD-2), performed well at a hydraulic retention time (HRT) of 1.0 d. Chemical oxygen demand (COD) removal efficiencies of up to 90% (avg. 53%) for AD-1 and 83% (avg. 60%) for AD-2 at organic loading rates (OLR) of 9.56 and 4.62 kg COD.m-3.d-1, respectively, were obtained. High sulphate (S04) removal efficiencies of up to 96% (avg. 86%) for AD-1 and 98% (avg. 82%) for AD-2 were also achieved, respectively. A maximum total solid (TS) removal of 65% (avg. 25%) for AD-1 and 62% (avg. 28%) for AD-2 was reported. An average methane content of 80% (AD-1) and 79% (AD-2) with average methane yields per COD removed of 2.19 and 1.86 m3. kg CODremoved.df-o1r AD-1 and AD-2 were found, respectively. When the same digesters (AD-1 and AD-2) were combined in a muItiphase series configuration, a total COD removal efficiency of up to 97% (avg. 80%) at an OLR of 8.32 kg COD.m-3.d-1,was achieved. Excellent total S04 removals of 96% (avg. 69%) were accomplished. Up to 82% TS (avg. 29%) was also removed during this study and the biogas consisted of 89% methane (avg. 79%). For this multi-phase combination up to 92% volatile fatty acids (VFA) (avg. 48%) were removed, indicating possible selective phase separation of the respective fatty acid producing/utilising bacterial populations. The use of a laboratory-scale UASB bioreactor with recirculation, resulted in COD removal efficiencies of up to 96% (avg. 51%) at an HRT of 3.0 d, and 95% (avg. 54%) at a HRT of 1.0 d. Low performances were generally found, with average S04 and TS removals of 59% (max. 97%) and 26% (max. 67%), respectively at an HRT of 1.0 d. The biogas production was very low throughout the study (0.05 - 0.63 I,d-1 ). A pilot-scale UASB reactor (300 I) was constructed and performed satisfactory with a 58% average COD removal and maximum of 96%. S04 and TS removals up to 96% (avg. 44%) and 93% (avg. 63%), respectively, were obtained. The methane content of the biogas was 85%. The pilot-scale studies were conducted under actual field conditions, where various shock and organic loads had to be absorbed by the system. The pilot-scale contact configuration (300 I) did not perform satisfactory as a result of continuous blockages experienced in the feed and recirculation lines. Maximum COD, S04, VFA and TS removal efficiencies of 41% (avg. 27%), 62% (avg. 41%), 64% (avg. 27%) and 39% (avg. 21%), respectively, were obtained. The results of all the studies indicated acceptable COD removals with increasing OLR's. Indications of the presence of active methanogenic and sulphate-reducing bacterial populations were apparent throughout the studies. One possibility for the successful start-up and commissioning of the anaerobic reactors was the use of a well-adjusted biomass, which consisted of highly selected and adapted microbial consortium for the specific gelatinmanufacturing effluent. It was clear from this study that gelatin-manufacturing effluent can be treated successfully, especially with the use of the UASB design. A welldefined data base was constructed which could be of great value for further upscaling to a full-scale digester.

AFRIKAANSE OPSOMMING: 'n Hoogs besoedelde industriele uitvloeisel word gegenereer deur die plaaslike gelatien-vervaardigings industrie. As gevolg van toenemende streng beperkings op die kwaliteit van uitvloeisels wat bepaal word deur die Nasionale Water Wet van 1998 en Nasionale Omgewings Bestuurs Wet van 1998, asook toenemende munisipale heffings wat geimplementeer word via Plaaslike Munisipale Wette, word die industrie verplig om die uitvloeisel vooraf te behandel. 'n Studie is onderneem om die lewensvatbaarheid van anaërobe behandeling van gelatien-vervaardigings uitvloeisel te ondersoek, aangesien anaërobe verterings tegnologie alombekend is vir die goeie sukses behaal in die behandeling van hoë-sterkte, komplekse uitvloeisels. Verskeie laboratorium- en loods-skaal studies is gedoen, met verskillende hibried Opvloei Anaërobe Slykkombers (OAS) en kontak ontwerpe. Goeie werksverrigting was verkry by 'n hidroliese retensie tyd (HRT) van 1.0 d met twee mesofiliese laboratorium-skaal hibried OAS verteerder ontwerpe wat uitgevoer was met poli-etileen (AD-1) en poli-uretaan (AD-2) materiaal. Chemiese suurstof behoefte (CSB) verwyderings van so hoog as 90% (gem. 53%) vir AD-1 en 83% (gem. 60%) vir AD-2 by organiese ladingstempo's (OLT) van 9.56 en 4.62 kg CSB.m-3.d-1,was onderskeidelik verkry. Hoë sulfaat (S04) verwyderings van tot 96% (gem. 86%) vir AD-1 en 98% (gem. 82%) vir AD-2 was ook onderskeidelik verkry. 'n Maksimum totale vaste stof (TVS) verwydering van 65% (gem. 25%) vir AD-1 en 62% (gem. 28%) vir AD-2 is gerapporteer. 'n Gemiddelde metaan inhoud van 80% (AD-1) en 79% (AD-2) met 'n gemiddelde metaan opbrengs per CSB verwyder van 2.19 en 1.86 m3.kg CSBverwyder.dv-i1r AD-1 en AD-2, was onderskeidelik gevind. Met die aanwending van dieselfde twee verteerders (AD-1 en AD-2) in 'n series gekoppelde multi-fase konfigurasie, is 'n totale CSB verwydering so hoog as 97% (gem. 80%) verkry by 'n OLT van 8.32 kg CSB.m-3.d-1. Uitstekende totale S04 verwydering van 96% (gem. 69%) is behaal. Tot 82% TVS (gem. 29%) was vewyder gedurende die studie en die biogas het uit 89% metaan (gem. 79%) bestaan. Vir die multi-fase kombinasie is 'n maksimum van 92% vlugtige vetsure (WS) (gem. 48%) verwyder, wat dui op die moontlike skeiding van selektiewe fases van die onderskeie vetsuur produserende/verbruiker bakteriële populasies. CSB verwydering van tot 96% (gem. 51%) by 'n HRT van 3.0 d en 95% (gem. 54%) met 'n HRT van 1.0 d was verkry, tydens die gebruik van In laboratorium-skaal OAS bioreaktor met hersirkulasie. Lae werksverrigting was oor die algemeen waargeneem, met gemiddelde S04 en TVS verwyderings van 59% (maks. 97%) en 26% (maks. 67%) by In HRT van 1.0 d. Die biogas produksie was baie laag gedurende die studie (0.05 - 0.63 I,d-\ In Loods-skaal OAS verteerder was opgerig en bevredigende resultate was verkry met In gemiddeld van 58% CSB verwydering en maksimum van 96%. S04 en TVS verwyderings so hoog as 96% (gem. 44%) en 93% (gem. 63%) is onderskeidelik verkry. Die metaan inhoud van die biogas was 85%. Die loods-skaal studie was uitgevoer gedurende ware veld kondisies, waartydens verskeie skok en organiese ladings deur die sisteem geabsorbeer is. Die loods-skaal kontak konfigurasie (300 I) het nie bevredigende resultate getoon nie, as gevolg van voortdurende blokkasies wat ondervind is in die toevoer en hersirkulasie pype. Maksimum CSB, S04, WS en TVS verwyderings van 41% (gem. 27%), 62% (gem. 41%), 64% (gem. 27%) en 39% (gem. 21%) was onderskeidelik verkry. Die resultate van al die studies het aanvaarbare CSB verwydering aangedui by toenemende OLT's. Indikasies van aktiewe metanogene en sulfaat-reduserende bakteriële populasies was ook teenwoordig gedurende die studies. Die suksesvolle aansit-prosedure en begin van die anaërobe verteerders kan toegeskryf word aan die gebruik van In goed aangepaste biomassa, wat uit hoogs selektiewe en aangepaste mikrobiese populasies vir die spesifieke uitvloeisel bestaan. Hierdie studie het getoon dat gelatien-vervaardigings uitvloeisel suksesvol met die OAS ontwerp behandel kan word. In Goed gedefinieerde data basis kan voorsien word, wat van groot waarde sal wees vir verdere opgradering na In volskaalse verteerder.

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