Dewatering and Sediment Processing

Sevenson’s sediment dewatering equipment includes:

Recessed Chamber Presses – Sevenson incorporates recessed chamber presses to dewater sediments and sludges. To optimize liquid-solid separation, recessed-chamber presses typically include filter aids, such as lime, polymers, or diatomaceous earth. Incorporating these materials shortens process cycle times and produces a low-moisture filter cake.

Geotextile Tubes – Geotextile tubes facilitate sediment dewatering via gravity through porous fabric. The dewatering process is aided by polymer addition to promote better solids capture resulting in a clearer filtrate. Sampling and/or permit requirements determine whether filtrate can be direct discharged or require wastewater treatment for additional processing. Flow rates for geotextile tubes are usually 2,000 to 5,000 GPM depending on tube sizes and laydown area.

Total Clean™ – Hydrocyclones and screening/desanding plants are often used in conjunction with sediment dewatering generated by hydraulic dredging. Total Clean™ is often the first step in a two-part dewatering process designed to operate in series. Total Clean™ is a scalping and desanding system used to size and separate dredged sediment. The second step, for materials not desanded by the Total Clean™ system, is to use geotextile tubes, settling ponds, or filter presses. The Total Clean™ unit receives the initial flow directly from the dredge and removes all the oversize debris, typically 1/4 inch+. The remaining slurry is then pumped to the hydrocyclone/shaker units where the +74-micron sand fractions are removed. Any solids remaining in the hydrocyclone overflow and screen underflow then flow through the tilted plate baffle section of the V-Tank. Remaining solids settle and are conveyed to the recycle pumps by the shaftless auger and then through additional sets of hydrocyclone/shaker units for additional removal of solids, down to +37 microns.

Belt Presses – These are commonly implemented to dewater biological wastewater sludge from process treatment plants or biological wastewater settling ponds. Belt presses are particularly effective when processing sludge with high-moisture content.

Centrifuges – Two-phase high-volume centrifuges are cost-effective technologies for large remediation projects requiring sludge dewatering. These units are normally operated at high-centrifugal forces (2,000–3,000 g’s) and produce relatively dry filter cake and high-quality effluent. This technology eliminates the need for bulking agents (polymer flocculent is typically added), resulting in reduced solids volume and mass.

Three-phase horizontal and vertical disc centrifuges (8,000–10,000 g’s) are used as process systems when specifications for oil and grease production are stringent (e.g., 0.5–1.0 percent bottom sediment and water). These units are widely used in the petroleum/petrochemical industries to process oily sludges, such as K048 waste streams or split-phase rag-layer emulsions, which can be produced by large dewatering operations.