Filtration Mechanism

Water flows downward through sand bed. Particles trap in void spaces between sand grains. Surface filtration captures large particles. Depth filtration removes finer solids throughout bed. Combined action achieves target water clarity.

Vessel Configuration

Vertical pressure vessel with raw water inlet distributor, sand bed typically 24-36 inches depth, gravel support layers preventing sand loss, underdrain system collecting filtered water and distributing backwash, filtered water outlet. Design per ASME Section VIII.

Sand Media

Graded silica sand with effective size 0.45-0.55mm, uniformity coefficient under 1.5. Proper grading ensures effective filtration without excessive pressure drop. Rounded grains preferred over angular for better backwash cleaning.

Operating Pressure

Typical 50-100 psig service pressure. Clean bed pressure drop 5-8 psi increasing to 15-25 psi as solids accumulate. High differential pressure indicates backwash needed restoring capacity.

Backwash Operation

Upflow water at 12-15 gpm per square foot expands bed 30-40% washing trapped solids to waste. Backwash duration 10-15 minutes. Air scour optional for heavily loaded applications. Proper backwash critical for maintaining performance.

Material Selection

Carbon steel with epoxy lining for municipal water. Stainless steel for process applications. FRP construction for corrosive waters. Internal distribution systems corrosion-resistant. External coating protects atmospheric exposure.

Filtration Performance

Removes particles 20-50 microns and larger. Reduces turbidity from 10-20 NTU to under 5 NTU. Efficiency depends on loading rate typically 2-5 gpm per square foot.

Applications

Municipal water treatment, industrial process water clarification, cooling tower makeup pre-treatment, boiler feedwater filtration, swimming pool water treatment, and any application requiring turbidity and suspended solids removal.

Run Time

Operates 12-48 hours between backwashes depending on inlet solids loading. Pressure drop or turbidity breakthrough signals backwash requirement. Automated controls optimize cycles.

Control Systems

Automated backwash initiation based on differential pressure, time, or turbidity. Sequential operation for multiple filter installations. Programmable logic controllers manage complete cycle including rinse.

Support Layers

Gravel layers 12-18 inches total thickness support sand preventing loss through underdrain. Graduated sizes from coarse at bottom to fine supporting sand. Proper support bed critical for system integrity.

Performance Benefits

Simple economical filtration technology. Minimal maintenance requirements. Long media life 10-15 years. Effective turbidity and suspended solids removal. Proven municipal and industrial applications.

Construction Standards

Pressure vessels per ASME Section VIII. Materials for water service. Underdrain design preventing media loss. Complete documentation with hydraulic calculations and performance specifications.

ERGIL sand filter vessels provide reliable economical water filtration removing suspended solids and turbidity in municipal and industrial applications.