Auto-Vac™ Rotary Vacuum Drum Precoat Filter for Industrial Wastewater Treatment
Industrial wastewater treatment gets more complex as solids loading increases, particle size decreases, and discharge requirements tighten. When gravity separation and clarification no longer provide consistent control, a rotary vacuum drum precoat filter offers a practical path forward for solids removal and dewatering.
The Auto-Vac™ system by ALAR is a rotary vacuum filter built around precoat microfiltration rather than mechanical screening or settling alone. As ALAR’s flagship dewatering technology, Auto-Vac™ handles a wide range of wastewater volumes and solids concentrations while maintaining stable filtration rates under changing operating conditions. Its operating approach focuses on controlled solids capture, moisture removal, and predictable effluent quality without reliance on extensive auxiliary equipment.
Industrial Wastewater Challenges That Require Vacuum Drum Precoat Filtration
Industrial wastewater systems are often asked to handle more solids, finer particles, and greater variability than they were originally built for. As production rates shift and wastewater chemistry changes, gravity separation and basic clarification can struggle to keep up. Fine suspended solids, precipitated metals, and de-emulsified fat, oil, and grease are especially difficult to manage through settling alone.
Operational costs add another layer of pressure. Sludge volumes increase, hauling becomes more frequent, and additional chemical pretreatment is introduced to compensate for inconsistent separation. These conditions typically signal the need for a rotary vacuum drum precoat filter that can impose mechanical control on solids removal. A properly applied rotary vacuum drum precoat filter captures micron-scale solids while actively removing moisture, helping stabilize and support more predictable disposal outcomes.
What Sets the Auto-Vac™ Apart From Conventional Wastewater Equipment?
The Auto-Vac™ rotary vacuum drum precoat filter incorporates design features that support stable filtration under real operating conditions.
Key characteristics include:
- A non-segmented drum design that allows vacuum to pull liquid through 100% of the filtration surface
- High usable vacuum levels, supporting faster filtration rates and improved moisture removal
- Incremental solids and media removal that maintains filtration rates without full cleaning cycles
- Precoat microfiltration capable of retaining fine suspended solids, precipitated metals, and de-emulsified fat, oil, and grease
- Reduced reliance on auxiliary equipment, limiting the need for extensive pretreatment chemicals, clarifiers, or DAF systems
These features allow the vacuum drum precoat filter to perform consistently across changing wastewater profiles while maintaining a compact footprint.
How the Auto-Vac™ Rotary Vacuum Drum Precoat Filter Achieves Controlled Microfiltration
The Auto-Vac™ system applies rotary vacuum drum precoat filter technology in a controlled, repeatable process based on solids capture, moisture removal, and media renewal.
1. Precoat Formation and Drum Construction
The core of the system is a hollow, rotating drum fitted with a wedge-wire screen and covered with a polypropylene filter cloth. Before filtration begins, the drum surface is coated with a consumable filter aid media cake, typically diatomaceous earth or perlite. This porous layer forms the primary filtration surface and allows water and air to pass through while retaining fine suspended solids.
The drum rotates in a filter pan with approximately one-third of its surface submerged in wastewater and the remaining surface exposed to ambient air. Wastewater enters the pan at a controlled rate, allowing consistent contact between the liquid stream and the filter cake.
2. Vacuum Application and Liquid Removal
A liquid ring vacuum pump applies suction to the interior of the drum. As the drum rotates, the vacuum pulls liquid through the filter cake, cloth, and screen while drawing moisture out of the solids retained on the media surface. Clarified liquid is removed from the system, while solids accumulate on the filter cake with each revolution.
The filtration-grade media used by ALAR can capture particles down to 1 micron or less, allowing clean effluent to pass while trapping larger suspended particles.
3. Solids Accumulation and Knife Blade Advancement
As solids build on the filter cake, resistance increases, and liquid flow slows. When the vacuum can no longer draw water efficiently, a stepping motor advances a variable-speed knife blade across the drum surface. The blade removes the accumulated solids along with a thin layer of spent filter aid, exposing a fresh porous layer beneath.
Filtration resumes immediately after this incremental removal. By renewing only the surface layer, the rotary vacuum filter maintains consistent performance while keeping filter aid consumption proportional to incoming solids loading.
How ALAR Applies the Auto-Vac™ in Wastewater Treatment Systems
At ALAR, the Auto-Vac™ is applied as part of an integrated wastewater treatment approach. Each installation begins with a technical evaluation of wastewater composition, solids behavior, flow variability, and discharge requirements.
These factors guide system configuration, including drum sizing, vacuum selection, filter aid choice, and control strategy. Auto-Vac™ systems are configured to integrate with existing treatment infrastructure, whether installed as part of a new process or incorporated into an established system. Startup support and operational tuning help ensure the rotary vacuum drum precoat filter performs as intended as wastewater conditions evolve.
Flexible System Sizing for Real-World Industrial Wastewater
Drum Size and Filtration Area
ALAR custom builds 16 Auto-Vac™ sizes, ranging from small units to systems exceeding 500 square feet of filtration area. Drum size is selected based on flow rate and solids loading to maintain stable vacuum conditions and avoid excessive cake buildup.
Filtration Rate and Vacuum Demand
Feed rate, vacuum capacity, and drum rotation speed are balanced to control resistance across the filter cake. Liquid ring vacuum pump capacity is matched to application requirements to support consistent moisture removal without overloading the system.
Filter Aid Consumption and Cake Thickness
Filter aid consumption scales linearly with influent volume and solids loading. Operators can adjust drum speed, knife advance, and liquid level in the filter pan to fine-tune filtration behavior as conditions change. Each batch cycle typically operates for several hours before media renewal, allowing predictable operation and maintenance planning.
ALAR custom builds sixteen (16) Auto-Vac™ sizes; ranging from 3.14 to 503 square feet of filtering area. The systems are available in automatic (PLC and pneumatic control) or semiautomatic (switch and valve control) options.
The patented design features a non-segmented drum that allows 27" of vacuum to pull liquid through 100% of the filter surface. This equates to faster filtration rates, drier solids, less filter aid consumption and a smaller footprint (less square footage needed).
ALAR engineered the Auto-Vac™ with variable adjustments for more efficiency. The operator can control the speed of the drum rotation and knife advance, along with the liquid level in the filter pan. Each independent function contributes to maximum effluent and dry solids quality.
The filter aid media provides "single-pass" absolute microfiltration with every revolution of the drum. When saturated with solids, the contaminated media is scraped off to expose a clean filter layer. This media protects the filter cloth from contamination by preventing direct contact with contaminated liquid. Filter aid consumption is linear to the incoming liquid volume and solids loading. ALAR will help determine the square feet of filtering area, and the amount of filter aid needed per batch. The cake layer of media will be spent after each filtration cycle (typically every 5 to 7 hours), then reapplied when the next batch cycle begins. ALAR is one of the largest distributors of bagged Diatomaceous Earth and Perlite filter aid; providing customers with competitive bulk pricing.
ALAR warehouses all major component parts; which are available for next-day delivery. This includes vacuum pumps, whereas other RVDF companies have 10 to 20 week lead times.
Contact ALAR to discover how the easy to operate Auto-Vac™ can benefit your bottom line.
Auto-Vac™ Sizing Rotary Vacuum Drum Precoat Filter Drum sizes are determined not by how much water is going to the Auto-Vac™ filter, but by how fast the volume flows through the Auto-Vac™ filter media.
The filtration rate is based upon square footage, because the filter (if flattened) is square.
The formula is:
(Gallons of Wastewater ÷ gph/ft2) ÷ Hours = ___ Ft2
ALAR has sixteen (16) filter drum sizes to choose from. The solids loading, volume and amount of hours per day will factor into the drum size needed.
The consumable filter aid precoat media is adjustable [linear] to the incoming volume. However, the filter drum should be sized to handle full-flow capacity.
| Model Number | Drum Diameter (Feet) | Drum Length (Feet) | Nominal Filtering Area (Square Feet) |
Overall Filter Skid Size (W x L) |
Overall Auxiliary Skid Size (W x L) | Maximum Height (Feet) | Approximate Shipping Weight (Lbs.) | Total Connected Horsepower |
|---|---|---|---|---|---|---|---|---|
| AV110 | 1 | 1 | 3.1 | 4'-2" x 8'-1" | - | 6'-3" | 1,900 | 4 |
| AV210 | 2 | 1 | 6.2 | 6'-5" x 7'-11" | - | 7'-1" | 2,800 | 6 |
| AV220 | 2 | 2 | 12.6 | 6'-5" x 8'-11" | - | 7'-1" | 3,000 | 7 |
| AV230 | 2 | 3 | 18.8 | 6'-5" x 10'-9" | - | 7'-1" | 3,200 | 9 |
| AV240 | 2 | 4 | 25.1 | 7'-11" x 11'-11" | - | 7'-5" | 3,400 | 11 |
| AV330 | 3 | 3 | 28.3 | 8'-8" x 11'-3" | - | 7'-5" | 5,300 | 13 |
| AV340 | 3 | 4 | 37.7 | 8'-7" x 12'-7" | - | 8'-0" | 5,500 | 13 |
| AV360 | 3 | 6 | 56.5 | 9'-0" x 16'-8" | - | 8'-6" | 6,200 | 20 |
| AV640 | 6 | 4 | 75.4 | 9'-8" x 9'-9" | 7'-2" x 13'-0" | 8'-7" | 10,100 | 33 |
| AV650 | 6 | 5 | 94.2 | 9'-8" x 11'-8" | 7'-2" x 13'-5" | 8'-4" | 11,300 | 48 |
| AV660 | 6 | 6 | 113 | 9'-8" x 12'-8" | 8'-1" x 14'-0" | 8'-3" | 11,700 | 48 |
| AV690 | 6 | 9 | 170 | 9'-11" x 14'-7" | 8'-5" x 18'-3" | 10'-5" | 14,800 | 69 |
| AV6120 | 6 | 12 | 226 | 10'-1" x 17'-7" | 8'-4" x 18'-9" | 10'-0" | 18,000 | 99 |
| AV8120 | 8 | 12 | 302 | 12'-1" x 19'-0" | 8'-4" x 26'-6" | 10'-9" | 24,300 | 99 |
| AV8160 | 8 | 16 | 402 | 12'-1" x 23'-6" | 10'-2" x 26'-6" | 12'-1" | 36,000 | 140 |
| AV8220 | 8 | 20 | 503 | 12'-1" x 27'-1" | 10'-2" x 29'-10" | 12'-5" | 41,000 | 140 |
Replacement Parts
ALAR designs each system to meet the customer's build-to specifications. ALAR begins with stock layouts, and customizes the auxiliary equipment according to the customer's specifications.
These stock layouts are available in PDF format. Contact ALAR for more information.
Case Studies
5 Benefits of the Auto-Vac™ Rotary Vacuum Drum Filter
Why settle with conventional wastewater equipment when the ALAR® Auto-Vac™ is a cost-effective solution to regulatory discharge and solids disposal compliance?
ALAR Replaces Clarifier & Filter Press - Reduces Heavy Metal
Learn how the Auto-Vac™ AV360 helped filter 5000-gallons of chemically treated acid tank dump and produce an overall savings of about $6,000 per month!
Auto-Vac™ Offers Solution for Latex Paint Wastewater
PPG’s Plant took steps to enhance its existing wash water and wastewater management program by implementing an in-house chemical treatment and dewatering system from Alar.
Frequently Asked Questions About the Auto-Vac™ Rotary Vacuum Drum Precoat Filter
A rotary vacuum drum precoat filter is typically used for industrial wastewater streams containing fine suspended solids, precipitated metals, or de-emulsified fat, oil, and grease that do not separate reliably through settling alone. Applications with variable solids loading or changing influent chemistry often benefit most from vacuum-based filtration.
A rotary vacuum drum precoat filter provides continuous, one-pass wastewater filtration with consistent flow, while filter presses operate in batches and can slow as plates blind. ALAR’s Auto-Vac® can capture particles smaller than 1 micron compared with about 25 microns for a filter press, helping improve discharge compliance. It also produces drier, more landfill-ready solids, reduces plate-cleaning labor, and is more forgiving of higher solids, oils/grease, polymer overdoses, and wastewater slugs. Filter presses often require more operator attention, cleaning, and downstream drying.
Pretreatment requirements vary by application. In many cases, a vacuum drum precoat filter can reduce or eliminate the need for extensive pretreatment equipment by directly capturing fine solids. The need for upstream treatment is determined by influent composition and discharge objectives.
Filter aid media is consumed gradually as solids are removed and the filtration surface is renewed. Replacement frequency depends on incoming solids loading, wastewater volume, and operating conditions rather than a fixed schedule.
