Holding Tank Purpose

Sludge from thickeners or clarifiers requires storage buffering between batch production and continuous dewatering. Holding tank provides inventory enabling dewatering equipment operation independent of upstream generation. Mixing prevents settling maintaining pumpable consistency.

Tank Design

Cylindrical atmospheric vessel with sloped or conical bottom, multiple inlet connections from thickeners, mechanical mixer preventing settling, outlet to dewaering pumps, level instrumentation, vent connections, access manholes.

Mixing System

Top-entry agitator with propeller or turbine impeller creating circulation. Variable speed control adjusts intensity for sludge consistency. Proper mixing prevents stratification and dead zones. Motor sized for sludge viscosity at 3-8% solids.

Material Construction

Carbon steel with protective coating or stainless steel resisting sludge chemistry. FRP construction for corrosive applications. Sloped bottom facilitates complete drainage. External coating protects atmospheric exposure.

Sludge Characteristics

Thickened sludge typically 3-8% solids from gravity thickeners or DAF. Viscosity varies with solids content and composition. Primary sludge less viscous than biological sludge. Design accommodates expected properties.

Capacity Sizing

Volume provides 12-48 hours storage at average sludge production. Adequate capacity allows flexible dewatering schedules. Balance between operational flexibility and tank size. Typical municipal plants 20-30 hours detention.

Level Control

High level indicates storage nearing capacity requiring dewatering rate increase. Low level protects dewatering pumps from starvation. Controllers coordinate with upstream thickening and downstream dewatering.

Odor Control

Covered tanks with odor control scrubber minimize emissions. Biological sludge generates odors from anaerobic activity. Proper ventilation and treatment required near populated areas. Sealed tank design contains vapors.

Applications

Municipal wastewater treatment sludge handling, industrial biological treatment plants, water treatment plant sludge systems, and any facility dewatering sludge requiring surge storage with mixing.

Polymer Addition

Conditioning polymer injection in holding tank improves dewatering. Mixing time allows polymer-sludge interaction before dewatering equipment. Enhanced flocculation increases solids capture and cake dryness.

Pump Interface

Progressive cavity or diaphragm pumps transfer viscous sludge to dewatering equipment. Adequate suction head prevents cavitation. Variable speed matches dewatering feed requirements.

Homogenization

Continuous mixing blends sludge from different sources equalizing characteristics. Uniform feed to dewatering improves performance versus variable sludge properties. Stabilizes dewatering equipment operation.

Performance Benefits

Provides operational flexibility through sludge storage. Mixing prevents settling maintaining pumpable consistency. Enables independent operation of thickening and dewatering equipment. Improves overall sludge handling efficiency.

Construction Standards

Atmospheric tank per API 650 or equivalent. Mixer per ANSI/AGMA standards. Materials for sludge service. Proper venting and odor control. Complete documentation with capacity calculations.

ERGIL sludge holding tanks provide storage and homogenization maintaining pumpable thickened sludge for efficient dewatering in wastewater treatment facilities.