Experimental Study On Sediment Vacuum Dehydration Of Aggregate Processing Wastewater

Studying team carried out the settlement and dewatering properties pilot test of the aggregate processing wastewater wastewater during August to December of 2009 which was based on the Daluo aggregate processing system of Guandi Hydropower Station. The pilot test had put forward wastewater treatment process of rectangular classification settlement and sludge treatment process of classification dewatering. The pilot test through studied different methods of dehydration and factors related to dewatering. It is the basis for further expanding the scale of the wastewater treatment process applied to the aggregate processing system and exploiting dewatering equipment.The pilot scale test model size was analog amplified by using fluid calculation software FLUENT in which operating parameters used were obtained in the pilot model. Studying team had developed a vacuum dewatering equipment with environmental protection equipment factory. Through experimentalizing on the pilot scale test model, studying team had further inspected universality of wastewater treatment process and further look for the treatment operating conditions which is more applicable to the pilot scale test site.Through a large number of field test data, the following conclusions were drawn: sediment particle size in the sediment is the main factors affect the dehydration performance of sediment, It is feasible to treating sediment hierarchically. It is finally ensure the HRT of the pilot scale test model tank is 20 and 40min.When the Influent flow is13m³/h, the first sediment particle size is big, dewatering performance is good. The Sediment dewatering performance can come to its best when the wet sediment was laid on the filter cloth is about 2 cm in thickness, and dried sediment thickness is about 1cm .When the dewatering prototype run Stably whose dewater capacity of first sediment is about 165kg /m²·h.The secondary wastewater sediment was difficult to be dewatered Whose Specific resistance is 2.49×10⁹cm/g.Because particle size which is less than 38μm is accounted for 67.48%, the effective way to dehydrate sediment is enhanced vacuum dewatering and adding flocculating agent can obviously improve dehydration characteristics .Under optimal coagulant dose(0.9‰) ,the specific resistance can reduce to 8.39×10⁸cm/g. The factors affect vacuum dehydration are the use of flocculants, the vacuum, the mud-cake thickness and filter cloth aerated amount. The sludge can be dewatered most efficient if the dried sediment thickness is about 1cm, which was based on the separation of the sludge from water.The sediment specific resistance in flocculation and sedimentation tank is 9.55×10¹⁰cm/g. Under optimal coagulant dose(10‰) ,the specific resistance can reduce to 8.39×10⁸cm/g.Considerting filter cloth aperture was too large to intercept the sedimentation of flocculation and sedimentation tank and the optimal coagulant dose is similar between secondary wastewater sediment and flocculation and sedimentation tank sediment ,so studying team chose to mix flocculation and sedimentation tank sediment and secondary wastewater before dewatering them.The mixed sediment was difficult to be dewatered Whose Specific resistance is 10.7×10⁸cm/g.When choosing enhanced vacuum dewatering, the effective way to dehydrate sediment is adding flocculating agent to improve dehydration characteristics .Under optimal coagulant dose(0.9‰) ,the specific resistance can reduce to 8.39×10⁸cm/g. The factors affect vacuum dehydration are the use of flocculants, the vacuum, the mud-cake thickness and filter cloth aerated amount. The sludge can be dewatered most efficient if the dried sediment thickness is about 0.5cm,which was based on the separation of the sludge from water. When the dewatering prototype run Stably whose dewatering capacity of mixed sediment is about 187kg / m²·h.The capacity of dewatering sediment of all levels sedimentation tank can met design requirements fully. After a period of operation, the dewatering prototype appeared some shortcomings, such as: airtightness between filter cloth and vacuum chuck is inadequate, pumping travel is too short which result in high energy consumption, The sediment was laid inhomogeneous after sediment quenched and tempered, filter belt deviated running easily. According to the disadvantages appeared. Dewatering prototype capacity will be improved greatly once some improved optimizations were propsed.This paper discussed different methods of dehydration and factors related to dewatering. It is the basis for further Project Scale of the wastewater treatment process applied to the aggregate processing system and improving dewatering prototype.