Recovery of Consolidated Rich Sludge as Fertilizer from Palm Oil Mill Effluent (POME) with Geotube® Dewatering Technology

The treatment of palm oil mill effluent (POME) typically involves the discharge of waste through a series of anaerobic and aerobic ponds to break down the waste. The waste is then discharged into the natural water body if no further water treatment is required. However, the process is complicated as heavy tropical rain affects the stability and consistency of the process.

The Challenge

Most POME plants discharge sludge into the ponds to the point of complete siltation. The silt is then either excavated and disposed, or new ponds are constructed. Millers continually face the incessant cycle of resolving the problem as pond volume decreases, complicated further by the continuous rapid sludge build-up in the anaerobic pond. As POME sludge levels in the ponds reaches its maximum limit, the cost of dewatering ponds became increasingly exorbitant.

The Solution

Part 1: TenCate Geotube® Dewatering

By dewatering the POME sludge using TenCate Geotube® units, the solid particles can be retained within the tube, and the liquid discharged is either recycled back through the plant or discharged out through the polishing ponds. In addition, solids within the Geotube® units offer a protected environment that facilitates the  acceleration of microbial breakdown of waste.

The POME sludge does not require polymer dosing and will be discharged into the Geotube® units to improve the purity of discharge water, and accelerate the drying process. The Geotube® units are filled with sludge directly from the anaerobic pond. Despite not adding polymer, the POME sludge can dewater well. Once dry, the Geotube® units are slit open and the degraded mulch can be used as fertilizer. Individual Geotube® units supplied to POME applications are manufactured from fabrics designed specifically for organic waste dewatering and sized to meet plant discharge volume and land space available for the deployment of the Geotube® units.

TenCate Geotube® units offer the following benefits:

• higher tube solids capacity
• faster dewatering and by-product generation
• significantly lower overall cost per m³ slurry processed
  

Part 2: TenCate Geotube® Silt Curtain

The treatment of palm oil effluent is typically processing organic-rich wastewater and recovery of solids through a series of ponds. Water clarity in the ponds can be assisted by deploying silt curtains designed to encourage the settlement of suspended solids.

Geotube® silt curtains are flexible barriers comprising engineered fabrics that slows down water flow and encourage suspended fine particles to settle at the bottom of the pond. When combined with other systems such as aerators, significant improvement can be seen in pond BOD and overall pond water management efficiency.

By understanding the mill process, waste stream volume and the available space for construction, TenCate Geotube® technical specialists were able to design an effective solution that optimizes the dewatering process.

The Performance

This project illustrates the functionality of Geotube® dewatering technology for the recovery of consolidated rich sludge as fertilizer for recomposting. Major cost savings were derived as the use of Geotube® dewatering units eliminated the need for constructing additional ponds and the value of consolidated sludge recovered were used to offset the cost of recovery. The combined solutions of Geotube® dewatering and silt curtain systems added significant efficiency to the overall process and returns from the recovery. 

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TenCate Geotube® dewatering units for POME sludge

Typical heavily silted POME sludge pond

TenCate Geotube® dewatering platforms

Dry cake from TenCate Geotube® dewatering units

Disposal of dewatered cake

View of anaerobic pond with TenCate Geotube® Silt Curtain and submersible mixer in operation

TenCate Geotube® Silt Curtain encourages the settlement of suspended solids to achieve water clarity in the polishing ponds

Aerial view of aerobic pond with TenCate Geotube® Silt Curtain