Microbial Community and Suspended Solid Removal in Anaerobic Hybrid Reactor of Palm Oil Mill Effluent

Name: Kanlayanee Meesap

keyword: anaerobic hybrid reactor

Abstract: Anaerobic hybrid reactor (AHR) has been applied in palm oil mill effluent treatment (POME) system. It is composed of two parts: the upper part or packed zone contains media supports to serve as a fixed film (FF) bioreactor and lower part or sludge zone is the upflow anaerobic sludge blanket (UASB) section where flocculants and granular sludge are developed. Residual suspended solid (SS) and oil and grease (O&G) in POME are the main causes that affect the process performance and stability of AHR as well as changes in microbial activity and population. Thus, the aims of this research were to study the effects of SS and O&G concentrations on process performance and stability including microbial characteristics in terms of microbial community, population and microbial activity in sludge and packed zones of AHR. The study consisted of four operational phases; low-strength (5-7 g SS 1 the power of -1 and 0.9-1.4 g O&G 1 the power of -1), high-strength (10-11 g SS 1 the power of -1 and 1.9-2.3 g O&G 1 the power of -1), shock load (12.5 g SS 1 the power of -1 and 2.7 g O&G 1 the power of -1), and recovery with operational back to 10 g SS 1 the power of -1 and 1.8 g O&G 1 the power of -1, with constant HRT at 5 days. At low-strength POME operation, the normal condition of process stability in both the sludge and packed zones was detected. The range of pH 7.1 to 7.3 and TVA/Alk was 0.20 to 0.43. Reactor performances were achieved at 50-90, 65-76 and 50-80% of TCOD, SS and O&G removal, respectively. However, low methane yield at 0.13-0.20 1 CH4 g the power of -l CODremoved was obtained because most of the organic compounds were used for microbial growth and less remained for methane production. High-strength POME not only promoted the process performance in organic removal but also increased methane production rate. At 10 g SS 1 the power of -1 operation, maximum methane yield at 0.30 1 CH4 g the power of -l CODranoved.Was obtained. Moreover, the number of non-methanogens and methanogens were found at 10 the power of 7-10 the power of 8 and 10 the power of -_ 10 the power of 6 copies rDNA g the power of -lVSS, respectively. Microbial activities and communities increased corresponding to the organic load. High non-methanogenic activity (1.32-1.65 g COD g the power of -lVSS d the power of -l) was achieved in the sludge zone while high methanogenic activity (0.26-0.34 gCOD-CH4 g the power of -lVSS d the power of -1) was achieved in the packed zone of AHR. Fermentative bacterium communities detected were y-Proteobacteria, Pseudomonas sp. Bacteroidetes bacterium, and Clostridium. Methanosaeta sp. was dominant methanogen in acetoclastic methanogenesis pathway of methane formation. Nevertheless, high-strength POME with 11 g SS 1 the power of -1 and 2.3 g O&G 1 the power of -1 led to process performance deterioration. According to these results found that the sludge zone showed higher acidic condition than that packed zone due to high organic acid accumulation. High organic acid concentration affect to process performance in SS and O&G removal decreased to 50 and 40%, respectively. Biogas production rate decreased to 4,000 ml d the power of -1 and the methane yield was lower than 0.15 1 CH4 g the power of -1CODremoved due to the acidic condition which inhibited methanogenic activity. These results indicated that the high process performance and microbial activity were obtained under AHR operation at OLR less than 4.0 g COD 1 the power of -1 d the power of -1 with 10g SS 1 the power of -1 and 1.9 g O&G 1 the power of -1. Organic shock load was observed at reactor operation with OLR 6.0 g COD 1 the power of -1 d the power of -1, 12.5 g SS 1 the power of -1 and 2.7 g O&G 1 the power of -1 within 27 d of operation time. Decreasing of process performance and stability were observed. Sludge zone was violently affected from shock load higher than that packed zone due to suspended sludge characteristics, which is directly attacked by organic acid while packed zone was protected by biofilm forming. Under shock load condition, high acid tolerant non-methanogens could work but most of methanogens were completely inhibited. However, temporary organic shock load condition was recovered in a short time by effluent recirculation. Moreover, high process performance of reactor operational back to 10 g SS 1 the power of -1 and 1.8 g O&G 1 the power of -1 were achieved within 6 HRTs. High overall process performance and normal process stability were resumed by detecting higher than 50% organic removal and pH approaching to normal condition. High SS concentration which were accumulated and presented in POME influent influenced increasing of specific hydrolytic bacteria such as Bacillus and y.Proteobacterium, which were the key players of cellulose decomposer in anaerobic digestion system. The number of non-methanogenic and methanogenic populations increased to 10 the power of 7-10 the power of 9 and 10 the power of 3-10 the power of 5 copies rDNA g the power of -1VSS, respectively.

King Mongkut's University of Technology Thonburi. KMUTT Library

Address: BANGKOK

Email: info.lib@mail.kmutt.ac.th

Name: Pawinee Chaiprasert

Role: Advisor

Created: 2010

Modified: 2012-01-05

Issued: 2555-01-03

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: JGSEE276

eng

DegreeName: Master of Architecture

Level: Master's Degree

Descipline: Energy Technology

Grantor: King Mongkut's University of Technology Thonburi

©copyrights King Mongkut's University of Technology Thonburi

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