The function of the effluent treatment plant is to treat the mill liquid waste to levels within the prescribed limits set by the Department of Environment (D.O.E.).
Wastewater containing polluting substance i.e. organics is brought into contact with a dense population of micro-organisms for a duration sufficient for the microbes to break down and remove the pollutants to the desired levels.
The method of treatment in the mill is the anaerobic process. This process comprises four stages.
a) The anaerobic digestion in the acidification phase
b) The anaerobic digestion in the methanogenic phase
c) The quiescent facultative stage of aerobic digestion.
d) Further effluent treatment by aeration process through Mechanical Effluent Plant
The complete anaerobic digestion or bio-degradation of the mill effluent is a complex operation as this process requires the acid forming organisms to grow in harmony with the methanogenic formers. Any imbalance of activities of these two organisms would upset the digestion process.
The acid producing bacteria and their associated enzymes degrade most type of organic material into fatty acids. The methanogenic bacteria convert the soluble products of the acid produces into methane and carbon dioxide.
The acidification stage is controlled to promote the growth of the acid formers. While in the second stage i.e. the methanogenic phase, the environment is optimum to form the methane formers.
The effluent treatment plant in the mill comprises of the following:-
1) De-oiling tank
2) Buffer pond - 1
3) Anaerobic ponds - 4
4) Facultative ponds - 2
5) Sequential Batch Reactor (Mechanical Effluent Plant)
De-oiling tank
Sludge waste from the mill is pumped into the tank.
The purpose of this tank is to trap remnants of free oil and permit solids to settle out. Solids settled here should be removed on a regular basis in order that working levels be maintained.
Regular checks should be made and any trace of oil here must be recovered.
Buffer/Anaerobic Pond
There is one buffer pond. The acidification stage is a very rapid process converting the organic components of the waste water into volatile fatty acids (vfa) and depresses the pH of the system. However recycling of the anaerobic liquor is done here for buffering i.e.
a) Obtaining the desirable pH level
b) Cooling to obtain the desired temperature and
c) Seeding i.e. introducing active organisms population
The above is practised at this stage to prepare the feed before entering into the following four (4) anaerobic ponds.
Facultative Ponds
The use of anaerobic digestion alone would not be sufficient to meet the standards stipulated by DOE hence further treatment of effluent is necessary in the facultative. These facultative ponds are for quiescent aerobic respiration of the anaerobically treated waste water. These 2 ponds are in parallel and in these ponds sufficient oxygenation to the waste water is introduced. The effluent after sedimentation in these ponds is directed to the Mechanical Effluent Plant for further effluent treatment.
Operation procedures
Sludge Pits/De-oiling tank
1) Process Supervisors/operators are to visually check the pit on a regular basis throughout processing and ensure that traces of oil is recovered soonest possible.
Also when excessive trace of oil is sighted, immediate measures must be taken to trace and arrest the source of this excessive oil loss.
2) Schedule cleaning of the sludge pit and tanks must be instituted to remove solids/sand and any debris on a scheduled basis.
3) Pumps in this area must be checked to be in good operating condition. Any faults or malfunction noticed must be reported for immediate repair.
Buffering Ponds
1) Ensure that recycling of anaerobic liquor is carried out as per instruction.
2) Remove any solid scum/oil traces on a daily basis.
3) Ensure free flow into and out of the ponds.
Anaerobic
1) Monitor visually ponds bacteria for any signs of fouling.
2) Solids removal should be carried on a regular basis.
3) Ensure stirrer/mixers are operated as per instructions.
4) Ensure that in flow and outlet discharge is proper and feed to downstream ponds is regulated as required.
Facultative
1) Regulate final discharge as necessary.
2) Ensure solids recycling where necessary.
3) Ensure surface aerator at the last facultative pond running.
Sequential Batch Reactor (Mechanical Effluent Plant)
1) The main purpose of this system is to bring down the effluent parameter especially B.O.D to be less than ≤20ppm according to the regulatory of State Department Of Environment.
2) The plant consist of :
a. Clarifier Tank - 1 unit
b. Holding Tank - 2 units
c. Reactor Tank - 2 units
d. Clarified Water Tank - 1 unit
e. Carbon Filter - 1 unit
3) There are also blowers and pumps to facilitate the effluent treatment. The flowchart for the operation of the system is shown in the Attachment MOM-SBR-01
4) The treatment process of the Mechanical Effluent Plant consist of:
Flocculation Treatment
Raw effluent from facultative pond (last pond) is pumped into vertical steel clarifier. Flocculant agent and pH correction agent is dosed into the pipe before entering clarifier to ease coagulation process.
Pre-Aeration Process
The clarified raw effluent will flow into the 1st holding tank. Filling is estimated for 3hours.
While in the holding tank, the raw effluent is subjected to pre-aeration for 2hours before transfer to reactor tank.
Pre-aeration is done through fine air bubbles passes through an array of disc type diffuser at tank base.
SBR Process
The pre-aerated effluent from holding tank is transferred into the reactor tank via transfer pump.
The SBR process inside the reactor tank will be controlled through a preset time base on the following activity:
i) Filling - 3hours
ii) Slow Aeration - 2hours
iii) Fast Aeration - 4hours
iv) Settling - 2hours
v) Discharge - 3hours
Filling The pre-aerated anaerobic liquid is pumped from holding tank. During start-up, seeding of bacteria is carried out. The quantity from seeding is depend on the MLSS concentration in the reactor.
Slow Aeration While filling up of the pre-aerated anaerobic liquid half of the diffuser inside the tank will activate, via control valve install at the distribution header.
Fast Aeration Filling completed and full aeration process activate.
Settling To allow solids and liquids are separated under true quiescent conditions.
Discharge The treated of clarified supernatant is pumped into a final treated effluent tank storage.
The excess sludge will settle and remain in the reactor tank. Desludging will depend on the MLSS concentration, not to exceed 20-30% by ratio of the pre-treated anaerobic liquid. This can be done by taking sample and allow to settle naturally.
Standby The reactor tank ready for the next batch.
The treated water will overflow through a constant level flexible outlet into a transfer (clarified) water tank.
The clarified water enters into an activated carbon filter via booster pump, which act to polish the water before discharge out to water course. At this stage the B.O.D level should be ≤20ppm.
A reject line is installed to return treated effluent into anaerobic pond if the B.O.D level exceed 20ppm.
Significance of the various effluent parameters
For Palm oil mill effluent (as per the Environmental Quality Act) only seven parameters are required to assess the quality effluent before it can be discharged into the river course. For routine monitoring purposes (at mill level) two sample tests are sufficient namely temperature pH and alkalinity .
At the mill level only the following tests are determined
1) pH
2) alkalinity
The above tests are done once a week and sample is collected from final discharge of the Mechanical Effluent Plant.
Samples are also collected from the final discharge from the Mechanical Effluent Plant and effluent parameters tested by an accredited laboratory. This is carried out once a month and analysis results submitted to DOE on a quarterly basis.
Ref
Personnel Experience
Wastewater containing polluting substance i.e. organics is brought into contact with a dense population of micro-organisms for a duration sufficient for the microbes to break down and remove the pollutants to the desired levels.
The method of treatment in the mill is the anaerobic process. This process comprises four stages.
a) The anaerobic digestion in the acidification phase
b) The anaerobic digestion in the methanogenic phase
c) The quiescent facultative stage of aerobic digestion.
d) Further effluent treatment by aeration process through Mechanical Effluent Plant
The complete anaerobic digestion or bio-degradation of the mill effluent is a complex operation as this process requires the acid forming organisms to grow in harmony with the methanogenic formers. Any imbalance of activities of these two organisms would upset the digestion process.
The acid producing bacteria and their associated enzymes degrade most type of organic material into fatty acids. The methanogenic bacteria convert the soluble products of the acid produces into methane and carbon dioxide.
The acidification stage is controlled to promote the growth of the acid formers. While in the second stage i.e. the methanogenic phase, the environment is optimum to form the methane formers.
The effluent treatment plant in the mill comprises of the following:-
1) De-oiling tank
2) Buffer pond - 1
3) Anaerobic ponds - 4
4) Facultative ponds - 2
5) Sequential Batch Reactor (Mechanical Effluent Plant)
De-oiling tank
Sludge waste from the mill is pumped into the tank.
The purpose of this tank is to trap remnants of free oil and permit solids to settle out. Solids settled here should be removed on a regular basis in order that working levels be maintained.
Regular checks should be made and any trace of oil here must be recovered.
Buffer/Anaerobic Pond
There is one buffer pond. The acidification stage is a very rapid process converting the organic components of the waste water into volatile fatty acids (vfa) and depresses the pH of the system. However recycling of the anaerobic liquor is done here for buffering i.e.
a) Obtaining the desirable pH level
b) Cooling to obtain the desired temperature and
c) Seeding i.e. introducing active organisms population
The above is practised at this stage to prepare the feed before entering into the following four (4) anaerobic ponds.
Facultative Ponds
The use of anaerobic digestion alone would not be sufficient to meet the standards stipulated by DOE hence further treatment of effluent is necessary in the facultative. These facultative ponds are for quiescent aerobic respiration of the anaerobically treated waste water. These 2 ponds are in parallel and in these ponds sufficient oxygenation to the waste water is introduced. The effluent after sedimentation in these ponds is directed to the Mechanical Effluent Plant for further effluent treatment.
Operation procedures
Sludge Pits/De-oiling tank
1) Process Supervisors/operators are to visually check the pit on a regular basis throughout processing and ensure that traces of oil is recovered soonest possible.
Also when excessive trace of oil is sighted, immediate measures must be taken to trace and arrest the source of this excessive oil loss.
2) Schedule cleaning of the sludge pit and tanks must be instituted to remove solids/sand and any debris on a scheduled basis.
3) Pumps in this area must be checked to be in good operating condition. Any faults or malfunction noticed must be reported for immediate repair.
Buffering Ponds
1) Ensure that recycling of anaerobic liquor is carried out as per instruction.
2) Remove any solid scum/oil traces on a daily basis.
3) Ensure free flow into and out of the ponds.
Anaerobic
1) Monitor visually ponds bacteria for any signs of fouling.
2) Solids removal should be carried on a regular basis.
3) Ensure stirrer/mixers are operated as per instructions.
4) Ensure that in flow and outlet discharge is proper and feed to downstream ponds is regulated as required.
Facultative
1) Regulate final discharge as necessary.
2) Ensure solids recycling where necessary.
3) Ensure surface aerator at the last facultative pond running.
Sequential Batch Reactor (Mechanical Effluent Plant)
1) The main purpose of this system is to bring down the effluent parameter especially B.O.D to be less than ≤20ppm according to the regulatory of State Department Of Environment.
2) The plant consist of :
a. Clarifier Tank - 1 unit
b. Holding Tank - 2 units
c. Reactor Tank - 2 units
d. Clarified Water Tank - 1 unit
e. Carbon Filter - 1 unit
3) There are also blowers and pumps to facilitate the effluent treatment. The flowchart for the operation of the system is shown in the Attachment MOM-SBR-01
4) The treatment process of the Mechanical Effluent Plant consist of:
Flocculation Treatment
Raw effluent from facultative pond (last pond) is pumped into vertical steel clarifier. Flocculant agent and pH correction agent is dosed into the pipe before entering clarifier to ease coagulation process.
Pre-Aeration Process
The clarified raw effluent will flow into the 1st holding tank. Filling is estimated for 3hours.
While in the holding tank, the raw effluent is subjected to pre-aeration for 2hours before transfer to reactor tank.
Pre-aeration is done through fine air bubbles passes through an array of disc type diffuser at tank base.
SBR Process
The pre-aerated effluent from holding tank is transferred into the reactor tank via transfer pump.
The SBR process inside the reactor tank will be controlled through a preset time base on the following activity:
i) Filling - 3hours
ii) Slow Aeration - 2hours
iii) Fast Aeration - 4hours
iv) Settling - 2hours
v) Discharge - 3hours
Filling The pre-aerated anaerobic liquid is pumped from holding tank. During start-up, seeding of bacteria is carried out. The quantity from seeding is depend on the MLSS concentration in the reactor.
Slow Aeration While filling up of the pre-aerated anaerobic liquid half of the diffuser inside the tank will activate, via control valve install at the distribution header.
Fast Aeration Filling completed and full aeration process activate.
Settling To allow solids and liquids are separated under true quiescent conditions.
Discharge The treated of clarified supernatant is pumped into a final treated effluent tank storage.
The excess sludge will settle and remain in the reactor tank. Desludging will depend on the MLSS concentration, not to exceed 20-30% by ratio of the pre-treated anaerobic liquid. This can be done by taking sample and allow to settle naturally.
Standby The reactor tank ready for the next batch.
The treated water will overflow through a constant level flexible outlet into a transfer (clarified) water tank.
The clarified water enters into an activated carbon filter via booster pump, which act to polish the water before discharge out to water course. At this stage the B.O.D level should be ≤20ppm.
A reject line is installed to return treated effluent into anaerobic pond if the B.O.D level exceed 20ppm.
Significance of the various effluent parameters
For Palm oil mill effluent (as per the Environmental Quality Act) only seven parameters are required to assess the quality effluent before it can be discharged into the river course. For routine monitoring purposes (at mill level) two sample tests are sufficient namely temperature pH and alkalinity .
At the mill level only the following tests are determined
1) pH
2) alkalinity
The above tests are done once a week and sample is collected from final discharge of the Mechanical Effluent Plant.
Samples are also collected from the final discharge from the Mechanical Effluent Plant and effluent parameters tested by an accredited laboratory. This is carried out once a month and analysis results submitted to DOE on a quarterly basis.
Ref
Personnel Experience
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