Recovery Purpose

Filters backwash using 2-5% of production flow. Discarding backwash wastes water and increases disposal costs. Recovery tank collects backwash allowing reuse after settling reducing overall water consumption and wastewater generation.

Tank Design

Atmospheric storage tank with backwash inlet, settling time for solids separation, clarified water return to filter influent, sludge accumulation zone with periodic removal, level control, overflow protection.

Operating Principle

Backwash water containing suspended solids enters tank. Quiescent conditions allow settling. Clarified supernatant recycles to filter feed. Settled solids accumulate requiring periodic removal to waste. Typical recovery 70-90% of backwash volume.

Settling Performance

Residence time 2-4 hours allows particle settling. Clarified water turbidity typically 10-50 NTU suitable for filter influent. Heavy solids settle rapidly. Fine particles may remain requiring occasional waste discharge.

Material Construction

Carbon steel with epoxy coating or stainless steel for water service. FRP construction for corrosive applications. Sloped bottom facilitates sludge removal. External coating protects atmospheric exposure.

Capacity Sizing

Volume provides settling time for backwash from multiple filter cycles. Typical sizing 1.5-2x single backwash volume. Balance between recovery efficiency and tank size. Level control manages inventory.

Sludge Removal

Accumulated solids require periodic removal maintaining tank capacity. Manual drainage or automated discharge based on settled layer thickness. Concentrated sludge 5-15% solids for disposal. Removal frequency weekly to monthly.

Applications

Municipal water treatment plant filter backwash, industrial process water filtration, cooling tower makeup treatment, wastewater tertiary filtration, and any filtration system generating significant backwash volumes.

Water Quality

Recycled water slightly higher turbidity than raw water. Acceptable for filter influent as filters designed for raw water treatment. Monitoring ensures recovered water meets filter feed specifications.

System Integration

Automated controls return clarified water to filter feed maintaining production. Level switches coordinate with filter backwash cycles. Overflow discharges to waste during upsets preventing filter feed contamination.

Economic Benefits

Reduces freshwater consumption 2-5% through backwash recovery. Decreases wastewater disposal volumes and costs. Simple payback typically 1-3 years. Environmental benefits from water conservation.

Level Control

High level indicates adequate recovery capacity. Low level prevents inadequate settling time. Controls coordinate recovered water flow with filter operations.

Performance Benefits

Conserves water through backwash reuse. Reduces disposal volumes and costs. Simple proven settling technology. Minimal maintenance requirements. Improves plant water efficiency.

Construction Standards

Atmospheric tank per API 650 or equivalent. Materials for water service. Proper venting and overflow. Foundation for tank weight plus liquid. Complete documentation with capacity calculations.

ERGIL backwash recovery tanks reduce water consumption and disposal costs through filter backwash reuse in water treatment facilities.