Department of Bioprocess Technology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.Microbial Biotechnology and Biosafety Department Agricultural Biotechnology Research Institute of Iran ( ABRII ) Seed and Plant Improvement Institute ‘s Campus P.
O. Box: 31535-1897 Mahdasht Road, Karaj, IranDepartment of Biological Functions and Engineering, Graduate School of Life Science and Systems Engineering. Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Fukuoka, 808-0196, Japan.A undertaking supported by the Federal Land and Development Authority ( FELDA ) , Malaysia.
*Corresponding writer.E- mail: rafein @ biotech.upm.edu.my
Changes in the acetoclastic methanogenic activity in the 500 M3 closed digester armored combat vehicle ( CDT ) handling palm oil factory wastewater ( POME ) were studied throughout the 110 yearss runing period.
The acetoclastic methanogenic activity ( AMA ) trial was used to mensurate the acetoclastic methanogenic activity of the biomass nowadays in relation to the optimum operation of anaerobiotic digestion along with conventional controlled parametric quantities. Throughout the operating period, the AMA trials were carried out at different organic burden rates ( OLR ) from 0.5 up to 5.0 kilograms COD/ m3/ vitamin D and hydraulic keeping clip ( HRT ) every bit low as 10 yearss to detect possible methane production and the public presentation of the digester. The trial was carried out in 100 milliliters serum vial incorporating mixture of POME sludge and basal medium ratio 20:80 % ( v/v ) . The AMA values detected in this survey were in the reported scope of 0.04 to 0.
33 g COD/ g VSS/ vitamin D which indicates the activity of acetoclastic methanogens in the digester. This trial was important in finding public presentation of digester since activity values indicated the active acetoclastic methanogens nowadayss in the CDT and gave a better penetration in microbiological position in comparing with conventional parametric quantities measured.Keywords: Anaerobic digestion ; acetoclastic methanogenic activity ; POME
Anaerobic digestion of palm oil factory wastewater ( POME ) is going more attractive late for the intervention has good merchandises to be utilized.
Most of the palm oil Millss in Malaysia adopted application of pond/ laguna system in handling POME since such intervention offers the cheapest engineering with minimal care. However, with invention and promotion of recent engineering, the executions of anaerobiotic digesters for POME intervention are deriving acknowledgment. A few studies have shown promising applications of bioreactor and procedure designs in the intervention of POME such as the reversible anaerobic baffled reactor ( RABR ) ( Raof et al. , 2005 ) , upflow anaerobiotic sludge fixed-film bioreactor ( UASFF ) ( Najafpour et al.
, 2005 ) , modified anaerobiotic baffled bioreactor ( MABR ) ( Faisal and Unno, 2001 ) , upflow anaerobic sludge cover reactor ( UASB ) ( Borja and Banks, 1995 ) , thermophilic upflow anaerobic filter ( UAF ) ( Mustapha et al. , 2003 ) , anaerobic uninterrupted stirred armored combat vehicle reactor ( CSTR ) ( Tong and Jaafar, 2005 ) and closed digester armored combat vehicle ( CDT ) ( Yacob et al. , 2006 ) . Lab and pilot graduated table surveies have been conducted by these research workers intended to measure the effectivity of the engineering for POME intervention. In the procedure of measuring the public presentation of any anaerobiotic bioreactor several parametric quantities were used as indexs among them are volatile fatty acids ( VFA ) degree, organic affair remotion, pH, alkalinity, temperature and composing of biogas produced. Another possible trial to find the success of anaerobiotic digestion is acetoclastic methanogenic activity ( AMA ) .
AMA trial is a method to find the activity of acetoclastic methanogenic population in sludge and a bioreactor system ( Ince et al. , 1997 ) . It is a simple method utilizing substrates such every bit ethanoate as C and energy beginnings for the production of methane ( Ince et al. , 1997: Jawed and Tare,1999 ) by methanogenic bacteriums. This method is of import to measure the equal degree of activity of active methanogens exists in the anaerobiotic intervention systems ( Ince et al. , 1997 ) . As reported by Ince and coworkers ( 1997 ) , any impairment of an anaerobiotic system ‘s public presentation was due to a alteration in dominant methanogenic species or a lessening in the measure of active methanogens or a lessening in their activity.
Any imposed emphasis such as fluctuation in operational and environmental conditions may take to a alteration in species types and their comparative population degrees since each methanogenic group have their ain specific activity and growing conditions which straight affected the public presentation of an anaerobiotic bioreactor in footings of wastewater quality and methane output ( Harper and Pohland, 1986 ) . In this survey, the AMA trial was used as a tool to set up the relationship between the optimum operation of CDT and acetoclastic methanogenic activity during the POME intervention.
2. Materials and Methods
2.1 Sludges trying for AMA trial
Test sludge was obtained from the underside of the CDT handling POME at Serting Hilir factory in the province of Negeri Sembilan, Malaysia.
The POME sludge was collected by utilizing silicon tubings and rapidly placed into 1 L Schott bottle with modified chromium steel steel cap. The stopper was modified to keep anaerobiotic status inside the bottles that was flushed with industrial class 99 % N2 ( Malayan Oxygen Sdn. Bhd. ) . Microbial activities were kept by incubating the sludge samples at 370C or at room temperature prior usage as inoculant or for farther analytical intents.
2 Description of Closed Digester Tank
An industrial graduated table CDT designed by Sumitomo Heavy Industries Ltd. , Japan and constructed by FELDA Palm Industries Sdn. Bhd ( FPISB ) , Malaysia was used for this survey. The entire on the job volume of the digester is about 500 M3. This unit was installed with the opposition temperature sensor and pH investigation to supervise the temperature and pH of the procedure severally. The CDT was operated under mesophilic status.
The pH was controlled between 6.8 and 7.2 which was adjusted automatically utilizing Na hydrated oxide ( NaOH ) concentration 6.25 M. Influent COD was range 30,000 mg/L aa‚¬ ” 90,000 mg/L per twenty-four hours throughout this survey. The conventional diagram and get down up operation of the CDT was described before ( Yacob et al.
, 2006 ) . To get down the operation, the CDT system was fed with POME at an organic burden rate ( OLR ) of 0.5 kilograms COD/ m3/d with a HRT of 74.4 yearss without blending provided. The VFA concentration in the CDT was determined about 188 mg/L in the CDT, bespeaking an acceptable concentration of organic degrees before get downing the existent operation.
These controlled parametric quantities were monitored daily to forestall the souring and impairment of the CDT.
2.3 Media Preparation
Media solution used for AMA trial contains the similar constituents and the processs are adopted from Dolfing and Bloemen ( 1985 ) . The rigorous anaerobic methods developed by Hungate ( 1969 were adopted throughout these probes.
2.4 AMA trial unit
The experimental apparatus is shown in Fig.
1. Media solution incorporating Na ethanoate was dispensed in serum bottles up to 80 milliliters and purged with N2 gas. Then the serum bottles were capped with butyl gum elastic stopper and aluminium seal. After autoclaving, the media were chilling down at room temperature anterior vaccination with 20 milliliters of CDT sludge. No vitamin and hint component was added in the trial medium since the AMA trial was monitored in 24 h reaction and no important growing of methanogens growing at short period ( Dolfing and Bloemen, 1985 ) .
The contents of the serum bottle were assorted by twirling manually several times and samples were withdrawn with panpipes and acerate leafs for zero hr reaction ( 0 H ) . Biogas and methane gas production was measured at clip intervals ( 12 H ) . The full trial was conducted at 37AA°C and without blending provided. On completion, the sum of sludge ( VSS ) staying in the serum bottle was determined. The staying VSS and cumulative methane production were used to cipher the methanogenic activity.
2.5 Analytic Methods
Influent and wastewater samples were analyzed for chemical O demand ( COD ) and volatile fatty acids ( VFA ) one time every other twenty-four hours. Suspended solids ( SS ) and volatile suspended solids ( VSS ) were carried out at the terminal of every trial.
All analyses were carried out harmonizing to Standard Methods ( APHA, 1992 ) . Methane concentration was determined utilizing a portable methane analyser ( XP-314A, Shin-Cosmos Electrics Co. Ltd, Japan ) .
3. Consequences and treatment
AMA trial and CDT public presentation
Table 1 summarized the consequences on CDT public presentation in relation to AMA trial values. In the first hebdomad of operation, the CDT was fed with inflowing COD of natural POME in the scope 27,800 to 69,100 mg/L ( OLR= 0.5 kg COD/m3/d ) .
Average VFA and CH4 production determined in the reactor was 182 mg/L and 40 % severally. The reactor achieved 89 vitamin D HRT. The AMA trial in the first hebdomad was recorded 0.33 g COD / VSS / d. The OLR was so increased to 1.0 kilograms COD/m3/d on the 2nd hebdomad of operation with inflowing COD ranged from 36,200 to 74,600 mg/L recorded. However, the activity of AMA aggressively declined to 0.
09 g COD/ g VSS/ vitamin D at the 2nd hebdomad of bioreactor operation. This indicated that the highest activity value during the first hebdomad was attributed to freshly reassign fresh POME at the lowest OLR to trip the biomass ( Yacob et al. , 2006 ) . Then activity aggressively decreased likely due to OLR alterations that required adaptation period of methanogenic bacteriums to accommodate with a new environment ( McCarty, 1964 ) .The reactor was further supplied with higher OLR to supervise the reactor behaviour. There were fluctuations in AMA values observed when the system introduced to higher OLR, ( OLR 1- 3.
0 kilograms COD/ m3/d ) . However, VFA degrees recorded for this period was in the acceptable scope for methanogens growing ( 182- 208 mg/L ) . The AMA values were recorded low at this OLR may be due to less substrates introduced into the CDT resulted minimum sum of intermediates produced and short concatenation fatty acids like propionic, formic and butyric acids were readily being consumed by H oxidising methanogens before being converted into ethanoate. Despite the important decrease in activities of acetoclastic methanogens to every bit low as 0.04 g COD/ g VSS/ vitamin D at 2.
5 kilograms COD/m3/d methane concentration was still entering high aaˆ°A? 50 % emitted from CDT. This might hold been due to the production of methane from hydrogen-utilizing methanogens ( Jawed and Tare, 1999 ) .The reactor was supplied with OLR 3.5 kilogram /m3/d for 10 yearss. The inflowing COD concentration determined was in the scope from 45,700 to 62,300 mg/L. It is clear from Figure 2 showed that increases the OLR from 3.0 to 3.
5 kilograms COD/ m3/ vitamin D caused the accretion of VFA ( 318 mg/L ) . These observations are attributed to the addition of OLR and concentration of COD loads into the CDT which resulted in VFA accumulated ( Najafpour et al. , 2005 ) . At this phase, the CDT has achieved mean 16 500 HRT with 52 % methane produced and decrease in VSS content.
Decrease in VSS content was believed the active biomass had been washout during eating of influent since increasing of OLR has resulted in the higher sum of POME being introduced. AMA value determined at this phase was 0.13 g COD/ g VSS/ d. It was reported that, acetoclastic methanogens particularly Methanosaeta sp. was known as obligate ethanoate consuming methanogens, because of the low threshold of substrate concentration and longer period of duplicating clip every bit long as 12 yearss ( Taconi, 2004 ) . Then it shows beyond mark of recovery with increased in activity ( 0.
13 g COD / g VSS/ vitamin D ) . This may be likely due to stable microbic equivalent achieved by systems after CDT was supplied with POME at OLR 3.5 kilogram COD /m3/d for 10 yearss.The VFA value was increasing when supplied with higher OLR and methane production was recorded 55 % .
At the terminal of CDT operation, VFA concentration detected high with 977 mg/L and COD remotion efficiency was reduced to 92 % ( Figure 3 ) . These marks has showed the bioreactor has reached a critical degree in which VFA concentration reached near to 1000 mg/L and decrease of COD remotion efficiency ( Yacob et al. , 2006 ) . Despite entering a high of VFA concentration, mean methane production was 55 % from this phase. The activity values were kept remained at 0.1 g COD/ g VSS/d until the terminal of operation in which CDT was supplemented with POME at OLR 5.0 kilogram COD/ m3/d.The fixed sum of sludge / micro-organism to be tested in the experiments is the of import factor.
In this trial, 20 milliliter of sludge is supplied in 80 milliliters man-made medium with concluding volume 100 milliliter and about content 0.1 -0.2 g of VSS. This trial was used in order to find possible methane production capacity of the CDT system throughout the operation therefore leting suited OLR to be applied. Acetoclastic methanogens was the importance microbes that converted ethanoate to methane in the most anaerobiotic digesters and about 70 % of the methane is formed from ethanoate and the staying 30 % was from CO2 and H ( McCarty, 1964: Lay et al. , 1998 ) .
It should be noted that AMA tests merely mensurate the CH4 production from ethanoate, by and large referred to as the acetoclastic methanogenic activity and does non include methane produced by hydrogen-utilizing methanogenic bacteriums. However, the sludge obtained from this survey non merely consists of ethanoate consuming bacteriums, but it besides has hydrogen-utilizing methanogens that change overing H and other methylated compounds to methane ( Jawed and Tare, 1999 ) .
Biogas pilot works handling POME was successfully performed. From our observation, the AMA trial consequences have shown a better penetration into microbiological behavior and could be used as a tool to find optimal or maximal organic burden of anaerobiotic digestion systems. The activity values obtained from this survey are within those by and large reported, runing from 0.
1-1.0 g COD/g VSS/d. The highest OLR achieved during the survey period was 5.0 kilogram COD /m3 /d with 55 % methane concentration at less than 10 yearss HRT. Our hereafter survey of POME intervention will concentrate on microbic composing, activity and their distribution compared to conventional parametric quantities.
The undertaking was sponsored by FELDA Palm Industries Sdn. Bhd. ( FPISB ) , Malaysia and Japan Society for Promotion of Science ( JSPS ) .
The writers would wish to thank the direction of Serting Hilir Palm Oil Mill for their co-operation and kindness throughout the survey.