A conventional mechanically cleaned intake screen consumes 1–8 kW of continuous electrical power: motors driving raking mechanisms, spray pumps cleaning screen panels, sensors monitoring blockage. Over a 25-year service life, that screen consumes hundreds of thousands of kilowatt-hours and generates tonnes of CO₂ emissions from an operation whose fundamental purpose (separating debris from water) requires no energy input at all.
Gravity does the work. A Coanda screen uses the natural force of gravity to accelerate water, pass it through the slots of precision-fabricated wedge wire (V-wire) panels, and discharge debris: continuously, without electricity, without moving parts, without chemical addition. It is water filtration reduced to its physical essentials: a curved surface, a slot geometry, and gravity, which acts on the water without any external input.
As water utilities, municipalities, and industrial operators pursue net-zero targets, reduced carbon footprints, and green building certifications, the energy consumed by water infrastructure is under scrutiny. The intake screen (the first stage of every water supply chain) is where energy consumption can be removed most simply and most permanently.
Table of Contents
- The Energy Problem in Water Infrastructure
- How Gravity-Fed Filtration Works
- The Three Zeros: No Energy, No Moving Parts, No Chemicals
- Energy Comparison: Coanda vs. Conventional Intake Screens
- Carbon Footprint Reduction
- Contribution to Green Building Certifications
- Alignment with UN Sustainable Development Goals
- Nature-Based Solutions and the Coanda Approach
- Downstream Sustainability Benefits
- Applications Where Filtration Without Electricity Has the Greatest Impact
- Frequently Asked Questions
- References
The Energy Problem in Water Infrastructure
Water and wastewater systems are among the largest consumers of electricity in most municipalities. Water treatment plants consume approximately 0.5–2.0 kWh per cubic metre of water processed, with pumping accounting for 70–90% of a water treatment plant's total energy use [1][2]. Globally, the water sector accounts for approximately 4% of total electricity consumption: a share that is growing as treatment standards tighten and demand increases [1].
Within this pattern of energy use, intake screening represents a small but entirely eliminable component. A single mechanically cleaned fine screen at a municipal intake consumes 1–8 kW continuously: approximately 8,700–70,000 kWh per year. At a multi-intake system with dozens of screens, the aggregate consumption is substantial.
More importantly, the energy consumed by mechanical screens is functionally unnecessary. The physical process of separating debris from water does not require electricity. It requires a velocity differential between clean water passing through a screen and debris being carried across it. Gravity provides this velocity differential at no energy cost.
Every kilowatt-hour consumed by a mechanical intake screen is a kilowatt-hour that should not be consumed.
How Gravity-Fed Filtration Works
A Coanda intake screen operates on two physical principles (the Coanda effect and gravity-powered hydraulics) neither of which requires external energy [3][4].
Step 1: Acceleration. Water flows over a weir crest and down a curved acceleration plate. Gravity accelerates the thin sheet of water to high velocity: typically 2–3 m/s by the time it reaches the screen surface.
Step 2: Separation. The high-velocity sheet of water passes over the slots between the tilted wedge wires (V-profile wires). The Coanda effect causes the water to adhere to the wire surface and bend into the slot, passing through as clean filtrate. Debris and particles larger than the slot opening (0.5 to 2.0 mm, 1.0 mm standard; narrower slots on request) cannot follow the bend: they are carried across the wire tip by their momentum and continue downstream.
Step 3: Discharge. Clean water collects in a collection chamber below the screen and flows under gravity, without pumping, to the downstream system. Debris slides off the screen face and is discharged over the lower edge: returning to the natural watercourse.
Every stage (acceleration, separation, discharge) is powered by gravity. There is no pump, no motor, no electrical connection. The screen operates whenever water flows over the weir. It stops when the water stops. There is nothing to switch on, nothing to switch off, and nothing to fail between those states.
For a detailed technical explanation, see: What Is a Coanda Intake Screen? The Complete Guide.
The Three Zeros: No Energy, No Moving Parts, No Chemicals
Coanda screens achieve what no conventional fine-screening technology can match: the complete elimination of three operational inputs:
Zero Energy
The screen consumes exactly 0 kWh in operation. There is no electrical connection at the intake. For remote sites, off-grid projects, and developing regions without a reliable electricity grid, this is not just a sustainability advantage: it is a functional prerequisite. The screen works in locations where alternatives that need electricity simply cannot operate.
Zero Moving Parts
There are no motors, chains, sprockets, bearings, raking mechanisms, spray pumps, or drive systems. Nothing rotates, moves back and forth, or slides. The screen is a static welded stainless steel structure. This eliminates:
- Mechanical wear and the maintenance it requires
- Lubricant consumption and disposal
- Spare parts inventory and procurement
- Mechanical failure modes (seized bearings, broken chains, burned-out motors)
The design life of a Coanda screen (up to 25 years with correct material selection) is determined by corrosion chemistry, not mechanical wear, because there is no mechanical wear.
Zero Chemicals
No coagulants, flocculants, biocides, or cleaning chemicals are used in the screening process. The separation mechanism is purely physical: slot geometry and fluid dynamics. This means:
- No chemical procurement, storage, or handling at the intake
- No chemical residue in the screened water
- No chemical waste requiring treatment or disposal
- No regulatory compliance burden for chemical usage at the intake
The combination of these three zeros makes a Coanda screen the most sustainable first-stage water filtration technology available.
Energy Comparison: Coanda vs. Conventional Intake Screens
| Technology | Electricity Consumption | Annual Energy (kWh) | 25-Year Energy (kWh) | Annual CO₂ at 0.4 kg/kWh |
|---|---|---|---|---|
| Coanda screen | 0 kW | 0 | 0 | 0 kg |
| Mechanically raked bar screen | 1–3 kW | 8,700–26,300 | 218,000–657,000 | 3,500–10,500 kg |
| Travelling band screen | 2–5 kW | 17,500–43,800 | 438,000–1,095,000 | 7,000–17,500 kg |
| Electrically driven drum screen | 3–8 kW | 26,300–70,000 | 657,000–1,752,000 | 10,500–28,000 kg |
| Self-cleaning pump suction screen | 0.5–2 kW | 4,400–17,500 | 109,000–438,000 | 1,750–7,000 kg |
Over a 25-year service life, replacing a single travelling band screen with a Coanda screen eliminates 438,000–1,095,000 kWh of electricity consumption and 7–17.5 tonnes of CO₂ per year. For multi-screen projects, such as the TISKI (Trabzon Water and Sewerage Administration) municipal project in Türkiye, where 64 conventional intakes were replaced with Coanda screens, the total energy saved is measured in gigawatt-hours and hundreds of tonnes of CO₂ [5].
These are not projections or estimates. They are the arithmetic consequence of replacing a technology that consumes electricity with one that consumes none.
Carbon Footprint Reduction
For organisations reporting under carbon disclosure frameworks, Scope 2 emissions from purchased electricity are a standard reporting category. Every mechanical intake screen contributes to Scope 2. Every screen replaced with a Coanda screen removes that contribution permanently.
The carbon reduction is particularly significant for:
- Municipal water utilities pursuing net-zero operational targets: the intake screening stage is typically the easiest and most cost-effective point in the treatment chain to achieve zero emissions
- Hydropower operators whose entire value proposition is clean energy: an electrically powered intake screen at a renewable energy facility is an ironic contradiction that a Coanda screen resolves
- Industrial facilities reporting under ESG frameworks: eliminating intake screen energy is a quantifiable, permanent, and verifiable sustainability action
- Agricultural operations subject to carbon accounting: gravity-fed intake screening contributes to the farm's overall sustainability record
Contribution to Green Building Certifications
Two major green building certification systems recognise water infrastructure efficiency:
LEED (Leadership in Energy and Environmental Design)
LEED awards up to 11 points for water efficiency, representing one of the largest credit categories [6]. While LEED water efficiency credits primarily target indoor and outdoor water consumption, the broader LEED framework rewards energy efficiency across all building systems. Eliminating electrical consumption at the water intake stage contributes to:
- Energy and Atmosphere credits: reduced electricity demand from water infrastructure
- Innovation credits: passive water filtration without electricity as a design innovation
- Regional Priority credits: in water-stressed regions where sustainable water management is a priority
LEED-certified buildings collectively saved $149.5 million in water costs and $1.2 billion in energy costs from 2015 to 2018 [6]. Gravity-fed intake screening is one of the technologies that makes these savings possible.
BREEAM (Building Research Establishment Environmental Assessment Method)
BREEAM awards credits across water management categories including WAT 01 (Water Consumption), WAT 02 (Water Monitoring), and WAT 03 (Leak Detection) [7]. The system evaluates the sustainability of the entire water supply chain, including the energy consumed by water infrastructure. An intake screen that uses no electricity contributes to:
- Water category credits: sustainable water supply infrastructure
- Energy category credits: eliminated operational energy from intake screening
- Management category credits: reduced maintenance requirements and operational complexity
For project teams pursuing LEED Platinum, BREEAM Outstanding, or equivalent certification levels, the ability to demonstrate water filtration without electricity at the intake stage is a measurable advantage.
Alignment with UN Sustainable Development Goals
Coanda screen technology directly supports three UN Sustainable Development Goals:
SDG 6: Clean Water and Sanitation. Target 6.3 requires improving water quality by reducing pollution and minimising release of hazardous chemicals. Target 6.6 requires protecting water-related ecosystems. Coanda screens provide physical water filtration without chemical addition and include inherent fish protection through narrow slot widths and non-impingement design [8].
SDG 7: Affordable and Clean Energy. Target 7.3 requires doubling the global rate of improvement in energy efficiency. Replacing electrically powered intake screens with gravity-fed alternatives that use no electricity is a direct contribution to energy efficiency in the water sector: one of the largest global electricity consumers.
SDG 9: Industry, Innovation and Infrastructure. Target 9.4 requires upgrading infrastructure for sustainability with increased resource-use efficiency and greater adoption of clean technologies. Coanda screens represent infrastructure that is inherently clean: no emissions, no waste, no consumables.
For organisations reporting SDG alignment (including multilateral development banks, government agencies, and ESG-reporting corporations) installed Coanda screens provide documented, quantifiable contributions to multiple SDG targets.
Nature-Based Solutions and the Coanda Approach
The UN World Water Development Report (2018) defines nature-based solutions (NBS) as approaches that "use or mimic natural processes to enhance water availability, improve water quality, and reduce risks associated with water-related disasters" [8]. While NBS typically refers to wetlands, riparian buffers, and ecosystem restoration, the underlying principle is the same as a Coanda screen: using natural forces (gravity, fluid dynamics, physical geometry) instead of artificial energy inputs to achieve water management objectives.
A Coanda screen does not mimic nature. It applies physics. But it shares the core NBS characteristics:
- Powered by natural forces: gravity powers the entire process, just as gravity powers natural filtration through soil, sand, and gravel
- No chemical inputs: separation is physical, not chemical, just as natural filtration relies on physical exclusion and settling
- Self-regulating: the screen operates whenever water flows, adjusting throughput to available flow, just as natural systems respond to hydrological conditions
- Minimal ecological disruption: fish and aquatic organisms are swept over the screen rather than entrapped, and debris is returned to the natural watercourse
For project teams seeking to align with NBS frameworks while achieving performance standards that natural systems alone cannot guarantee, Coanda screens offer a hybrid approach: the sustainability characteristics of a nature-based system with the engineering precision of manufactured infrastructure.
Downstream Sustainability Benefits
The sustainability benefits of a Coanda screen extend beyond the screen's own operation without electricity:
Reduced chemical consumption downstream. Pre-filtration with narrower openings (slot openings of 0.5 to 2.0 mm, 1.0 mm standard, versus 25–150 mm bar spacing for conventional trash racks) removes more organic debris before water enters the treatment plant. Less organic material means lower coagulant dose, reduced disinfection byproduct precursors, and decreased sludge generation. Each of these reductions carries its own savings in energy, chemicals and carbon emissions.
Extended equipment life. Pumps, valves, membranes, and filter beds receiving cleaner intake water last longer, require fewer replacements, and consume less energy operating at design efficiency rather than degraded efficiency. The embodied carbon in manufacturing replacement equipment is avoided.
Reduced maintenance transport. For remote or distributed intake systems (such as the 64-site TISKI municipal project in Türkiye) eliminating routine mechanical maintenance eliminates the vehicle trips, fuel consumption, and emissions associated with maintenance crews accessing each site [5].
Reduced waste generation. No mechanical components to replace means no worn chains, burned-out motors, corroded sprockets, or spent lubricants entering the waste flow. The only waste from a Coanda screen operation is the debris that was already in the water: returned to the natural watercourse.
Applications Where Filtration Without Electricity Has the Greatest Impact
Operation without electricity is an advantage everywhere, but it is decisive in specific situations:
Off-grid and remote sites. Where no electrical grid exists (remote hydropower sites, rural agricultural intakes, island water supplies) a Coanda screen is not just more sustainable than an electrically powered screen. It is the only viable fine-screening option. See: Micro-Hydro Intake Screens.
Developing regions. Where grid electricity is unreliable, expensive, or unavailable, gravity-fed filtration provides consistent water screening without dependence on infrastructure that may not exist. The TISKI project demonstrated this on a large scale: 64 intakes operating continuously without electrical supply [5].
Net-zero facilities. For treatment plants, industrial facilities, and campuses pursuing net-zero operational emissions, eliminating intake screen electricity is one of the easiest and most permanent decarbonisation actions available.
Climate-resilient infrastructure. Operation without electricity means no vulnerability to power outages during storms, floods, and ice events. When the grid fails, a Coanda screen continues operating. See: Climate-Resilient Water Intake Infrastructure.
Green-certified projects. For projects pursuing LEED, BREEAM, or equivalent certification, intake screening without electricity provides quantifiable credits across energy, water, and innovation categories.
Frequently Asked Questions
How does zero-energy water filtration work?
Zero-energy water filtration uses gravity as the sole driving force. In a Coanda screen, water flows over a weir and down a curved acceleration plate: gravity accelerates it to high velocity. The sheet of water passes over the slots between the tilted wedge wires, where the Coanda effect causes clean water to adhere to the wire surface and bend into the slot, while debris is carried over the screen face. Clean water collects in a sump below. The entire process (acceleration, separation, collection and debris discharge) is powered by gravity. There is no electrical connection, no pump, no motor.
Can gravity-fed filtration work for large municipal water systems?
Yes. Coanda screens reach large capacities by combining several panels in an array. Each panel delivers approximately 140 l/s per metre of width on the US Bureau of Reclamation (USBR) reference geometry, and 150 l/s per metre on the ADENCO-127. For large municipal systems requiring hundreds or thousands of litres per second, multiple panels are arranged in parallel. The TISKI project in Türkiye installed 64 Coanda screens across a regional municipal drinking water system: all operating without electricity. The technology is not limited to small flows.
How much energy does a Coanda screen save compared to conventional screens?
A single conventional mechanically cleaned screen consumes 8,700–70,000 kWh per year depending on type and size. Over a 25-year service life, that totals 218,000–1,752,000 kWh. A Coanda screen consumes exactly zero kWh: the savings equal the full consumption of the conventional alternative. At an average carbon intensity of 0.4 kg CO₂/kWh, each screen replaced with a Coanda screen avoids 3.5–28 tonnes of CO₂ annually.
Does zero-energy mean zero maintenance?
Zero energy means zero electricity consumption: not zero maintenance. A Coanda screen requires annual visual inspection and periodic pressure washing, but there is no mechanical maintenance (no motors, chains, bearings, or spray nozzles to maintain). For the complete maintenance schedule with cost data from screens that have been in operation for 10+ years, see: Coanda Screen Maintenance.
Can a Coanda screen contribute to LEED or BREEAM certification?
Yes. While LEED and BREEAM do not have specific credits for intake screening without electricity, the technology contributes to multiple credit categories including energy efficiency (eliminated operational electricity), water efficiency (sustainable water supply infrastructure), and innovation (passive gravity-fed design). For projects pursuing high certification levels (LEED Platinum, BREEAM Outstanding), demonstrating water infrastructure that uses no electricity is a quantifiable advantage.
How does Coanda screening align with SDG 6?
Coanda screens directly support UN Sustainable Development Goal 6 (Clean Water and Sanitation) through SDG Target 6.3 (improving water quality without chemical addition), Target 6.6 (protecting aquatic ecosystems through fish-safe screen design), and broadly through SDG 7 (energy efficiency) and SDG 9 (sustainable infrastructure). For organisations reporting SDG alignment, installed Coanda screens provide documented, measurable contributions.
Is filtration without electricity reliable in all weather conditions?
In normal conditions (including rain, wind, seasonal flow variation, and moderate cold) yes. The debris removal mechanism operates continuously whenever water flows. In extreme cold (below approximately -14°C), frazil ice (small ice crystals carried in flowing water) can accumulate on the screen surface and anti-icing measures may be required. When heating is used, the screen consumes energy only during ice events (typically a few weeks per year), not continuously. See: Anti-Icing Technology for Water Intake Screens.
References
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"Energy Consumption in Water/Wastewater Treatment Industry: Optimisation Potentials." MDPI Energies, Vol 16, No 5, 2023. Retrieved April 2026, from https://www.mdpi.com/1996-1073/16/5/2433
-
"How Much Electricity Does a Wastewater Treatment Plant Use." Water & Wastewater. Retrieved April 2026, from https://www.waterandwastewater.com/how-much-electricity-does-a-wastewater-treatment-plant-use/
-
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
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Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
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"TISKI Case Study." Coanda Intake Screen / ADENCO. Retrieved April 2026, from http://coandaintakes.com/case-studies/tiski-case-study/
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"LEED and Water Efficiency Credits." Banyan Water / U.S. Green Building Council. Retrieved April 2026, from https://www.usgbc.org/credits?Category=%22Water+efficiency%22
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"BREEAM Water Requirements: How to Earn Certification Points with Water Management." Smartvatten. Retrieved April 2026, from https://smartvatten.com/en/blog/sustainability-esg/breeam-water-requirements
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"Nature-Based Solutions for Water." United Nations World Water Development Report 2018 / UNDP. Retrieved April 2026, from https://www.undp.org/publications/nature-based-solutions-water
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"Gravity Water Filter Market Size, Overview, Trends and Forecast 2025–2030." Virtue Market Research. Retrieved April 2026, from https://virtuemarketresearch.com/report/gravity-water-filter-market
-
IPCC (2022). "Chapter 4: Water." Climate Change 2022: Impacts, Adaptation and Vulnerability (AR6 Working Group II). Retrieved April 2026, from https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-4/
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"Gravity Filtration for Treatment Plants: Low-Energy Designs and Performance Optimization." Water & Wastewater. Retrieved April 2026, from https://www.waterandwastewater.com/gravity-water-filtration-treatment-performance/
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U.S. DOE (2025). "Life-Cycle Cost Analysis Framework for Water Efficiency Measures." Retrieved April 2026, from https://www.energy.gov/femp/articles/life-cycle-cost-analysis-framework-for-water-efficiency-measures
Published by ADENCO: Advanced Engineering Coanda Intake Screens. Zero energy. Zero moving parts. Zero chemicals. Every ADENCO Coanda screen operates on gravity alone and delivers sustainable, passive water filtration with the lowest possible environmental impact. Explore intake screens for your project that use no electricity →