Gypsum Sedimen Pond

1. The FGD pond system using natural vertical drain (water gravity) through filtration system
2. This is supporting facility for the normal FGD Chloride blow down operation i.e flow 600 – 750 LPM and TSS around 2- 3%. Above this normal operation is beyond pond’s drain capability.
3. During last operation, pond A has experienced with FGD dewatering system (rotary drum) and made more FGD blow down (flow and TSS) went to FGD pond A. The gypsum over flow to the pump pit had affected to pond system performance. Therefore, we need to conduct inspection to the pond A before re-utilize
4. Contaminated FGD chloride blow down with other material such as fly ash during Unit trip, start up, and shut down shall be prohibited to be put in the FGD sedimentation pond. It is considered will affect to FGD pond performance. During this abnormal condition, FGD Chloride blow down shall be put in the retention basin until normal condition.



Amount of truck from Pond A was 160 Dump Truck or 3,680 Tons gypsum send to Ash Yard, with assumption 23 ton/truck.

detail inspection in FGD pond A with the purpose to find out filtering system performance. The brief report as follow:
1. The 1st geo textile under the gypsum layer is in good indication. No significant gypsum penetrate indication.
2. The sand layer is in good condition. No indication gypsum penetrate into this layer
3. The 2nd geo textile under sand layer is in good condition.
4. The gravel condition is looking dirty. Some of gypsum penetrated to this layer (suspected due to overflow gypsum occurred into pump pit area). The amount of gypsum is not significant and it is still wet. Most probably could be cleaned easily using hydrant water through filtering pipe.
5. The filtering pipe is in good condition.

FGD pond B has been dredged. We also conducted filtration layer checking and found that fly ash contaminant didn’t penetrate to the gypsum working layer. The remaining gypsum working layer after dredging is about 20 cm.
Activity for pond B is continue with back flush water to find out the pond’s draining performance. Basically, it is showing no concern in the filtration layer. Technically, we could re-utilize this pond B for FGD blow down (subject to water pumping system condition). Meanwhile dredging in the pond A is ongoing progress.

Now, We have through one cycle of this FGD pond operation already i.e. during dry season and rainy season and collected all necessary information during this pond’s development.