ETP sludge dried to a fraction of its weight
How an effluent treatment plant producing 2,500 kg of filter-press cake a day can dry it with heat pumps and cut disposal weight, against a briquette-fired thermic fluid dryer.
▶Video: Industrial drying and dehumidifying
V09 · 2–2.5 minSludge, green-ware, pharma granules and storage rooms
Video coming soon01Problem statement
- Paying to transport water. Filter-press cake is still 70 to 80% water, so most of the landfill and transport bill is for water.
- Odour and handling. Wet biological sludge smells, attracts flies and leaks in storage and trucks.
- High-temperature dryers are risky. Thermic fluid paddle dryers run hot, need a firing attendant and can create dust and fire hazards with organic sludge.
- Losses between fuel and process. Burning briquettes in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference effluent plant serves a chemical and textile cluster. Its filter presses and decanter produce about 1,500 kg of chemical sludge and 1,000 kg of biological sludge a day, which go to a secured landfill by truck.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Chemical sludge (filter press) | Air 60–65 °C | 1,500 kg cake/day, 70% → 25% moisture | 900 | 1,620 |
| Biological sludge (decanter) | Air 55–60 °C | 1,000 kg cake/day, 82% → 25% moisture | 760 | 1,368 |
| Total | 1,660 | 2,988 | ||
Conventional hot-air dryers use about 1.8 kWh of heat per kg of water removed. That figure is the baseline the savings are measured against.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 1 × SE-AA-DR-84 (84 kW) heat pump drying module, removing about 1,660 kg of water a day in roughly 17 running hours.
- The briquette-fired thermic fluid paddle dryer stays connected behind a normally closed valve as standby.
- Cake from the filter press is extruded into strands onto a slow belt dryer, which gives a large surface for drying at low temperature.
- The dryer air loop is closed, so odour stays inside and only condensate leaves the dryer.
- Condensate returns to the ETP inlet for treatment.
Selected equipment
| Model | 1 × SE-AA-DR-84 |
|---|---|
| Heating capacity | 84 kW each, 84 kW total |
| Dehumidifying | about 98 L/h total (pro rata to the published 12–120 L/h range) |
| Drying air | rated 70 °C, 75 °C maximum |
| Refrigerant | R134a |
| Ambient | −5 to 43 °C |
| Water removed per kWh | about 2.4 kg |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TIC-201 holds drying air at 60–65 °C. Belt speed is set from the cake feed rate and an outlet moisture check, and the dryer runs continuously on the 20-hour schedule. The existing paddle dryer is kept as standby during maintenance.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of wet cake | – | – |
| CO₂ per year | – | – |
06Benefits
Lower disposal weight
Drying to 25% moisture cuts the mass sent to landfill by roughly two thirds.
Low-temperature safety
Drying at 65 °C avoids the dust explosion and smouldering risks of hot paddle dryers.
Contained odour
The closed air loop keeps smell inside the dryer housing.
Heat recovered from the moisture
The evaporator condenses water out of the air and the condenser puts that latent heat back into the drying air, so about 2.4 kg of water leaves per kWh of electricity.
Closed loop, clean product
Air recirculates inside the chamber. No dust, smoke or outside humidity reaches the product, whatever the weather.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Wet cake quantity per day from each source
- Cake moisture after the press or decanter
- Present disposal cost per tonne and distance to landfill
- Sludge type and analysis
- Space available near the filter press
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Sticky phase. Sludge passes a sticky, plastic phase at around 40 to 60% dry solids. Extruding thin strands and keeping the bed undisturbed avoids clumping on the belt.
- Corrosive vapours. Sludge releases ammonia and other corrosive vapours. Specify coated coils and stainless steel or coated casings for the dryer.
- Hazardous waste rules. Dried sludge remains hazardous waste. Check the consent conditions for storage and transport of dried cake.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
Talk to us
ETP sludge dried to a fraction of its weight
How an effluent treatment plant producing 2,500 kg of filter-press cake a day can dry it with heat pumps and cut disposal weight, against a briquette-fired thermic fluid dryer.
▶Video: Industrial drying and dehumidifying
V09 · 2–2.5 minSludge, green-ware, pharma granules and storage rooms
Video coming soon01Problem statement
- Paying to transport water. Filter-press cake is still 70 to 80% water, so most of the landfill and transport bill is for water.
- Odour and handling. Wet biological sludge smells, attracts flies and leaks in storage and trucks.
- High-temperature dryers are risky. Thermic fluid paddle dryers run hot, need a firing attendant and can create dust and fire hazards with organic sludge.
- Losses between fuel and process. Burning briquettes in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference effluent plant serves a chemical and textile cluster. Its filter presses and decanter produce about 1,500 kg of chemical sludge and 1,000 kg of biological sludge a day, which go to a secured landfill by truck.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Chemical sludge (filter press) | Air 60–65 °C | 1,500 kg cake/day, 70% → 25% moisture | 900 | 1,620 |
| Biological sludge (decanter) | Air 55–60 °C | 1,000 kg cake/day, 82% → 25% moisture | 760 | 1,368 |
| Total | 1,660 | 2,988 | ||
Conventional hot-air dryers use about 1.8 kWh of heat per kg of water removed. That figure is the baseline the savings are measured against.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 1 × SE-AA-DR-84 (84 kW) heat pump drying module, removing about 1,660 kg of water a day in roughly 17 running hours.
- The briquette-fired thermic fluid paddle dryer stays connected behind a normally closed valve as standby.
- Cake from the filter press is extruded into strands onto a slow belt dryer, which gives a large surface for drying at low temperature.
- The dryer air loop is closed, so odour stays inside and only condensate leaves the dryer.
- Condensate returns to the ETP inlet for treatment.
Selected equipment
| Model | 1 × SE-AA-DR-84 |
|---|---|
| Heating capacity | 84 kW each, 84 kW total |
| Dehumidifying | about 98 L/h total (pro rata to the published 12–120 L/h range) |
| Drying air | rated 70 °C, 75 °C maximum |
| Refrigerant | R134a |
| Ambient | −5 to 43 °C |
| Water removed per kWh | about 2.4 kg |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TIC-201 holds drying air at 60–65 °C. Belt speed is set from the cake feed rate and an outlet moisture check, and the dryer runs continuously on the 20-hour schedule. The existing paddle dryer is kept as standby during maintenance.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of wet cake | – | – |
| CO₂ per year | – | – |
06Benefits
Lower disposal weight
Drying to 25% moisture cuts the mass sent to landfill by roughly two thirds.
Low-temperature safety
Drying at 65 °C avoids the dust explosion and smouldering risks of hot paddle dryers.
Contained odour
The closed air loop keeps smell inside the dryer housing.
Heat recovered from the moisture
The evaporator condenses water out of the air and the condenser puts that latent heat back into the drying air, so about 2.4 kg of water leaves per kWh of electricity.
Closed loop, clean product
Air recirculates inside the chamber. No dust, smoke or outside humidity reaches the product, whatever the weather.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Wet cake quantity per day from each source
- Cake moisture after the press or decanter
- Present disposal cost per tonne and distance to landfill
- Sludge type and analysis
- Space available near the filter press
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Sticky phase. Sludge passes a sticky, plastic phase at around 40 to 60% dry solids. Extruding thin strands and keeping the bed undisturbed avoids clumping on the belt.
- Corrosive vapours. Sludge releases ammonia and other corrosive vapours. Specify coated coils and stainless steel or coated casings for the dryer.
- Hazardous waste rules. Dried sludge remains hazardous waste. Check the consent conditions for storage and transport of dried cake.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.