Operational enhancement of an upflow anaerobic sludge blanket reactor treating fog-reduced grain distillery wastewater

Van Der Westhuizen, Hendrik Schalk (2014-04)

Thesis (MScFoodSc)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Waste generated by the distillery industry is a major ecological concern and disposal thereof without a suitable treatment can have damaging effects on the environment. The characteristics of this type of wastewater are highly variable and dependent on the raw material used and production process followed. Grain distillery wastewater (GDWW) is also rich in fats, oils and grease (FOG). Successful treatments of distillery wastewater and GDWW have been reported using an upflow anaerobic sludge blanket (UASB) reactor technology. The aim of this study was to investigate the ability of lab-scale UASB reactor to treat FOG-reduced GDWW and the subsequent enhancement thereof following an unique feeding strategy approach. Firstly, a coagulation/flocculation-centrifugation step was developed to obtain FOG-reduced GDWW. Secondly, the efficiency of a lab-scale UASB reactor was investigated treating FOG-reduced GDWW at pre-determined operational parameters as well as the verification of biomass acclimatisation. Lastly, the effect of a unique feeding strategy of FOG-reduced GDWW to lab-scale UASB reactor granules was investigated in terms of COD, FOG-reduction and biomass acclimatisation. It was found that a coagulation/flocculation-centrifugation treatment removed sufficient amounts of FOG and TSS from GDWW. Different commercially available coagulation/flocculation products were evaluated whilst used in combination with a centrifugation step for improved sedimentation and separation. The FOG removal remained between 90 and 97% for the ferric chloride (FeCl3) and Ferrifloc 1820 treatments, respectively, whereas the TSS removal ranged between 56 and 93%, respectively. The use of a high molecular weight polymer (Ultrafloc 5000) and an aluminium chlorohydrate (Ultrafloc 3800) proved to be less effective in terms of FOG removal efficiency, ranging from 72 to 86%. It was decided to pre-treat GDWW with FeCl3 in combination with centrifugation to obtain FOG-reduced GDWW for subsequent UASB reactor treatment investigations. The FOG-reduced GDWW was fed into a laboratory-scale UASB reactor (2 L) over a period of 331 days. During the operational period different feeding parameters were attained to establish the ability of the UASB reactor to efficiently treat FOG-reduced GDWW. The COD removal increased from 60 to 85% at an organic loading rate (OLR) of ca. 5.5 kgCOD.m-3.d-1 (pH = 7.5) whilst FOG removal remained between 45 and 70%. COD removal increased to 90% with the attainment of an OLR of ca.10 kgCOD.m-3.d-1 (pH = 7.5) whereas FOG removal remained in the region of 55 and 65%. COD and FOG removal remained above 85% and 50%, respectively, when substrate pH was decreased to 6.50 (OLR ca. 10 kgCOD.m-3.d-1). A granule activity test was performed on seed and FOG-reduced GDWW fed granules to determine biomass acclimatisation. FOG-reduced GDWW fed granules showed higher activity in terms of methane production rate and cumulative methane production suggesting biomass acclimatisation. The FOG-reduced GDWW was fed to a laboratory-scale UASB reactor following a unique feeding approach. The feeding approach consisted of several feeding and starvation cycles. Improved average biogas production was observed during the feeding (0.26 to 11.3 L.d-1) and starvation (1.8 to 4.2 L.d-1) cycles as higher loading rates were obtained during each feeding cycle. After the completion of the strategic feeding the UASB reactor was continuously fed at an organic loading rate of ca. 5 kgCOD.m-3.d-1. The COD reduction efficiency improved from 70 to 80%, however, FOG removal remained in the region of 60%. Granule activity tests done on days 0, 215 and 279 showed improved UASB granule activity to FOG-reduced GDWW with operation time in terms of methane production rate and cumulative methane production. This study has proven that a coagulation/flocculation-centrifugation treatment of GDWW can remove sufficient amounts of FOG and TSS before the commencement of a UASB treatment, however, such a technique would require more refinement. It was also found that a UASB reactor can successfully treat FOG-reduced GDWW, however, it must be advised that close monitoring of the UASB reactor is required in order to maintain efficient COD reduction. A strategic feeding approach proved to be successful, but further improvement of the UASB efficiency to treat FOG-reduced GDWW in terms of stable COD and FOG reduction, stable effluent pH, improved biogas production and biomass activity must still be explored.

AFRIKAANSE OPSOMMING: Afloop water wat gegenereer word deur die distillerings-industrie veroorsaak ‘n ekologiese kommer en wegdoening daarvan sonder geskikte behandeling, kan ernstige gevolge op die omgewing hê. Die eienskappe van hierdie tipe afvalwater kan varieer en is afhanklik van die rou materiale gebruik en die produksie proses wat gevolg is. Graan distillery afloop water (GDAW) deel dieselfde eienskappe met die van distillery afloop water, alhoewel dit ook hoog is in vette, olies en ghries (VOG). Suksesvolle behandeling van distillery afloop water en GDAW met n opvloei-anaërobiese slykkombers (OAS) reaktor is deur verskeie navorsers gerapporteer. Die doel van hierdie studie was om die uitvoerbaarheid van laboratorium skaal OAS reaktor, wat VOG-verminderde GDAW behandel te ondersoek, asook die daaropvolgende verbetering deur n unieke voer strategie te volg. Eerstens, was ‘n koagulasie/flokkulasie-sentrifigasie tegniek ontwikkel om VOG-verminderde GDAW te kry. Tweendens, die effektiwiteit van ‘n lab-skaal OAS reaktor ondersoek, wat gevoer was met VOG-verminderde GDAW, by voorafbepaalde parameters. Laastens, die effek van ‘n unieke voer strategie van VOG-verminderde GDAW op lab-skaal OAS reaktor granules. Dit was vasgestel dat ‘n koagulasie/flokkulasie-sentrifigasie voor behandeling voldoende hoeveelhede VOG en TSS verwyder van GDAW. Verskillende kommersieel beskikbare koagulasie/flokkulasie produkte was in kombinasie met ‘n sentrifugasie stap geëvalueer om sedimentasie en skeiding te verbeter. Dit was nie ‘n plan om die stap te perfek nie, maar dat dit eerder sou dien as ‘n voorbehandeling stap vir opeenvolgende ondersoeke. Die VOG verwydering het tussen 90 en 97% gevariëer vir ferri chloride (FeCl3) en Ferrifloc 1820 (Chlorchem) en TSS verwydering het tussen 56 en 93% gewissel. Die gebruik van ‘n hoë molekulêre gewig polimeer (Ultrafloc 5000) en ‘n aluminium chlorohidraat (Ultrafloc 3800) was minder effektief met n VOG verwydering wat tussen 72 en 86% gewissel het. Die VOG-verminderde GDAW was in ‘n laboratorium-skaal OAS reaktor oor ‘n tydperk van 331 dae behandel. Verskillende voer doelwitte was geëvaluaeer om te bepaal of ‘n OAS reaktor GDAW suksesvol kan behandel. CSB afbraak het van 60 to 85% gestyg teen ‘n organiese lading van 5.5 kgCOD.m-3.d-1 (pH 7.50), met VOG verwydering wat tussen 45 en 70% gewissel het. Die CSB afbraak het na die bereiking van 10 kgCOD.m-3.d-1 (pH 7.50) gestyg na 90% met VOG afbraak tussen 55 en 60% gewissel het. Die CSB en VOG verwydering het bo 85% en 50% onderskeidelik gebly, met die verlaging van substraat pH na 6.50 (CSB ca. 10 kgCOD.m-3.d-1). ‘n Aktiwiteits toets is uitgevoer met saad granules en VOG-verminderde GDAW gevoerde granules. Granules (VOG-verminderde GDAW gevoer) het ‘n hoer aktiwiteit getoon teenoor saad granules in terme van metaan produksie tempo en kumulatiewe metaan produksie. Die VOG-verminderde GDAW was gevoer in ‘n OAS reaktor deur gebruik te maak van ‘n strategiese voertegniek. Die strategie het uit verskeie voer en hongersnood fases bestaan. Verbeterde biogas produksie was tydens voer (0.26 tot 11.3 L.d-1) en hongersnood (1.8 tot 4.2 L.d-1) -fases opgelet soos ‘n hoër lading bereik was. Na die voltooing van die strategiese voer fase was die OAS reaktor op ‘n deurlopende basis teen ‘n lading van 5 kgCOD.m-3.d-1 gevoer. Die CSB verwydering het van 70 na 80% verhoog terwyl VOG afbraak in die omgewing van 60% gewissel het. Biomassa aktiwiteits toetse was uitgevoer is op dag 0, 215 en 279 het verhoogde aktiwiteit vertoon, met ‘n strategiese fase en deurlopende fase teenoor die aanvanklike (ongeaklamatiseerde) granules. Hierdie studie het bewys dat ‘n flokkulasie/koagulasie-sentrifugasie behandeling van GDAW kan dien as ‘n voorbehandelings stap vir opeenvolgende OAS reaktor studies. Dit was gevind dat ‘n OAS reaktor die VOG-verminderde GDAW kan behandel, maar dit word aanbeveel dat die OAS reaktor so sorgvuldig as moontlik gemonitor word om effektiewe CSB verwydering te handhaaf. Ten slotte, ‘n strategiese voer strategie was suksesvol, maar verdere verbetering van die OAS reaktor ten opsigte van die behandeling van VOG-verminderde GDAW moet verder ondersoek word.

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