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Gravity Filters

Open-basin media filtration for large-volume water clarification at low operating cost.

Overview

Basiia designs and supplies gravity filter systems for large-volume water clarification in municipal water treatment, irrigation, and industrial applications. Gravity filters operate at atmospheric pressure using the hydraulic head of the water column to drive flow through a media bed — eliminating the need for high-pressure pumps and reducing operating costs versus pressure filtration. Our gravity filter packages include rapid gravity filters (RGF), slow sand filters (SSF), and travelling bridge backwash filters — designed to AWWA and Ten States Standards for potable water applications.

Typical Applications

  • Municipal potable water treatment from surface water sources
  • Large-volume industrial process water clarification
  • Irrigation water treatment from rivers and canals
  • Pre-treatment ahead of disinfection systems
  • Tertiary wastewater polishing for reuse
  • Stormwater harvesting and treatment
  • Agricultural water supply from surface water
  • Pre-treatment ahead of RO systems at large scale

Key Features

Engineered for Performance

Rapid Gravity Filters (RGF)

Concrete or steel open-basin rapid gravity filters with dual-media (anthracite/sand) or mono-media (sand) beds — operating at 5–15 m/hr filtration rate with automated backwash by air scour and water wash.

Slow Sand Filters (SSF)

Biological slow sand filters operating at 0.1–0.4 m/hr — relying on the Schmutzdecke biological layer for removal of pathogens, organics, and turbidity without chemical pre-treatment. Low energy, low maintenance, suitable for rural and remote applications.

Travelling Bridge Backwash

Automated travelling bridge backwash systems for large multi-cell gravity filter installations — providing sequential cell backwash without taking the entire filter bank offline.

Coagulation & Flocculation Pre-Treatment

Upstream coagulation (alum, ferric sulphate, or polyelectrolyte), flash mixing, and flocculation basins — conditioning the feed water for effective gravity filtration and turbidity removal.

Underdrain Systems

Concrete block, nozzle plate, or Leopold underdrain systems for uniform backwash distribution and filtered water collection — designed for the media depth, backwash rate, and filter cell dimensions.

Automated Backwash Control

PLC-based automated backwash initiation by turbidity breakthrough, head loss, or timed cycle — with air scour, sub-fluidisation wash, and final rinse sequences to restore filter bed performance.

Applicable Standards

  • ISO 9001
  • AWWA B100 (Granular Filter Material)
  • Ten States Standards (Recommended Standards for Water Works)
  • WHO Guidelines for Drinking-Water Quality
  • Local environmental and potable water regulations

Get in Touch

Discuss Your Gravity Filters Requirements

Our engineering team is available to review your project requirements and provide a technical proposal. Contact us to start the conversation.