Centrifugal Blowers and Sludge Dryers for Water Treatment Plants
Water treatment plants in India are under sustained regulatory pressure. CPCB effluent discharge standards, NGT compliance orders, and the scale of investment flowing through AMRUT 2.0 and the National Mission for Clean Ganga (NMCG) mean that ETPs, STPs, and CETPs across the country are either being built, upgraded, or audited right now. Every stage of that process — aeration, biological treatment, odour control, and sludge disposal — involves equipment that must run continuously, resist corrosive process environments, and hold up to operational demands that vary by feedstock and throughput.
AS Engineers supplies centrifugal blowers and sludge dryers to water treatment facilities across India. Both product lines are designed to application — not selected from a catalog — with MOC specified to the corrosive conditions of each process stream.
Centrifugal Blowers for Water Treatment
Aeration
Aeration is the single largest blower application in biological water treatment. Activated sludge systems, extended aeration tanks, and sequential batch reactors (SBRs) require a continuous, stable supply of air to sustain aerobic microbial activity. Under-aeration kills the biology. Over-pressurisation wastes energy and raises operating cost.
Backward curved centrifugal blowers are the preferred choice for clean aeration air — high efficiency at the operating point, stable pressure-flow characteristic, and non-overloading power curve. For fine bubble diffuser systems, consistent static pressure delivery across the depth of the aeration tank is the design requirement we engineer to.
Odour Control
Hydrogen sulphide (Hâ‚‚S) and ammonia are the primary odour compounds in municipal and industrial wastewater treatment. Plants located near residential zones are legally required under CPCB and state pollution control board norms to contain and treat these emissions. Chemical scrubbers and biofilters both need a forced-draft air supply to pull odorous gases from the source and push them through the treatment media.
Blowers for odour control duty handle mildly corrosive air streams. MOC selection — SS 304 or SS 316 depending on H₂S concentration — is determined at the design stage, not as an afterthought. Our industrial exhauster radial blowers are suited to this duty where gas-phase corrosion is a concern.
Air Stripping
Air stripping removes dissolved volatile organic compounds (VOCs) and ammonia from contaminated water by passing a counter-current airstream through a packed tower or tray stripper. The blower provides the forced-draft air supply. This application requires moderate to high static pressure at relatively low airflow, and the air stream may carry trace contaminants — which makes impeller material selection and shaft seal specification important.
Filter Backwash Air Scouring
Rapid sand filters and membrane bioreactors (MBRs) require periodic backwash to remove fouling and restore permeability. Air scouring — high-velocity air injected below the filter bed — loosens accumulated solids before water backwash clears them. High pressure radial blade blowers are the correct choice for this application: radial blade geometry handles particulate carry-over without buildup around the shaft, and the pressure range covers the static head of most filter bed depths.
Enclosed Space and Process Ventilation
Pump rooms, chemical dosing areas, and enclosed treatment tanks accumulate gases including H₂S, methane, and chlorine vapours. Forced ventilation by dedicated exhaust blowers maintains safe atmospheric conditions for operators and prevents gas accumulation above LEL thresholds. These blowers are typically sized for 6–12 air changes per hour depending on the classified area and gas generation rate.
Sludge Dryers for Water Treatment
ETP and STP sludge is a disposal liability. Wet sludge at 75–80% moisture content cannot be landfilled economically, transported without leakage risks, or co-processed in cement kilns at commercially viable rates. The disposal cost for untreated wet sludge runs at approximately Rs 25/kg. Drying the sludge changes that equation.
AS Engineers’ paddle dryer uses indirect heat transfer through hollow, wedge-shaped paddles carrying steam or thermic fluid. There is no hot air contact with the product. Heat passes entirely through the heated paddle surface into the wet sludge, which is agitated continuously by the counter-rotating dual shafts. The result: moisture content drops from a typical inlet of 40–85% down to an outlet of 5–15%, with an 80–90% reduction in sludge volume.
What this means for the buyer:
- Operating cost: Rs 5.45–7.50 per kg of dried output (at Rs 10/kWh power cost)
- Disposal cost avoided: approximately Rs 25/kg of wet sludge
- Payback period: 12–13 months for a 500 kg/day drying capacity
- Dried sludge calorific value: approximately 3,500 kcal/kg — viable for co-processing in cement plants or as auxiliary fuel
For ETP operators evaluating paddle dryers for the first time, AS Engineers offers a paddle dryer rental service — a trial run on your actual sludge before committing to capital purchase. This is not commonly offered by dryer manufacturers in India.
More technical detail on sludge drying applications is available at sludgedryer.in.
Application-to-Product Selection Table
| Water Treatment Application | Equipment Type | Key Design Parameter |
|---|---|---|
| Aeration (activated sludge, SBR) | Backward curved centrifugal blower | Stable pressure-flow curve, high efficiency |
| Odour control (scrubber / biofilter) | Industrial exhauster radial blower | Corrosion-resistant MOC (SS 304/316) |
| Air stripping (VOC / ammonia removal) | High pressure radial blade blower | Moderate pressure, corrosion-resistant shaft seal |
| Filter backwash / air scouring | High pressure radial blade blower | High static pressure, radial blade geometry |
| Process / enclosed space ventilation | Backward inclined centrifugal blower | Volume flow, safety-rated continuous duty |
| Sludge drying (ETP/STP biosolids) | Paddle sludge dryer | Indirect heat, inlet 40–85% moisture, outlet 5–15% |
| Dewatered cake drying | Paddle dryer | Indirect heat, sticky / abrasive media handling |
Why Water Treatment Buyers Work with AS Engineers
Water treatment is one of the more demanding procurement contexts for industrial equipment. The process media is corrosive. The duty cycle is 24/7. Regulatory compliance means downtime is not acceptable. And plant budgets — particularly in Urban Local Bodies and publicly funded projects — are subject to audit.
What we bring to this sector:
- Custom-engineered blowers to your airflow (CMH) and static pressure (mmWC) requirement, not catalog selection
- MOC specified to Hâ‚‚S concentration, temperature, and particulate loading: MS, SS 304, SS 316, SS 316L, Duplex SS 2205 available
- ISO 9001:2015 certified manufacturing with in-house performance testing and material test certificates
- 24+ years of engineering experience across ETP, STP, CETP, and industrial water treatment applications
- Paddle dryer rental service for sludge characterisation trials before capital commitment
- Full documentation support: performance test certificates, balancing reports, GA drawings
Frequently Asked Questions
What type of blower is used for aeration in activated sludge plants?
Backward curved centrifugal blowers are the standard choice for activated sludge aeration. They offer a stable, non-overloading power curve, high efficiency at the rated operating point, and quiet operation compared to positive displacement blowers. The correct sizing depends on your tank volume, diffuser submergence depth, SOTE requirement, and process oxygen demand. Share your process data with our engineering team and we will size accordingly.
What is the difference between a paddle dryer and a rotary drum dryer for sludge?
A paddle dryer transfers heat indirectly through the walls of hollow, heated paddles — the sludge never contacts hot air. A rotary drum dryer uses hot air in direct contact with the sludge to evaporate moisture. For ETP/STP sludge, the indirect contact paddle dryer is preferred because it handles sticky, high-moisture feeds, produces minimal dust, and allows vapour to be collected and treated rather than discharged as exhaust. It is also significantly more compact per unit throughput.
What inlet and outlet moisture content can the paddle dryer handle for ETP sludge?
Our sludge dryers handle inlet moisture in the range of 40–85% and reduce it to 5–15% at the outlet, depending on heating media temperature, residence time, and sludge characteristics. For sludge types outside this range or with unusual viscosity or abrasion properties, contact us with a sample or process data sheet before specifying.
What MOC is recommended for blowers in Hâ‚‚S-laden odour control duty?
For H₂S concentrations below 50 ppm in the airstream, SS 304 impeller and casing construction is typically sufficient. Above 50 ppm, or where the gas is wet and the temperature is below dew point, SS 316 or SS 316L is recommended. For particularly aggressive streams, Duplex SS 2205 provides better pitting resistance. We select MOC based on your gas composition and temperature data — not a default catalog option.
Can AS Engineers supply blowers for AMRUT 2.0 or government ETP/STP projects?
Yes. We supply to privately operated ETPs and to projects funded through AMRUT 2.0, Smart Cities Mission, NMCG, and ULB tenders. Our ISO 9001:2015 certification, material test certificates, and performance documentation meet the vendor qualification requirements of most project procurement frameworks. Contact us with your project specification for a technical and commercial response.
Your ETP or STP has specific airflow, pressure, and sludge disposal requirements. Generic equipment rarely fits. Send us your process data and our engineering team will size the right blower or sludge dryer for your application.
Phone: +91 99090 33851 | +91 82386 77554 Email: info@theasengineers.com