HMI symbols for water & wastewater treatment
Water and wastewater plants share a common process vocabulary: pumps, blowers, knife gates, decanter centrifuges, sludge presses, scrubbers, and a lot of instrumentation. This page walks the train from intake to discharge and, for each block, says what the symbol has to show and where to get it: symbols other engineers have published under CC BY 4.0, the free Symbol Builder when you need to draw your own, and the generic icon library for alarm badges, instrument bubbles and connection lines. Everything on a calm gray background, color reserved for state and alarms (ISA-101).
The water/wastewater process train
Most plants follow a similar block diagram. For each stage: the equipment you will have to represent, what matters on the symbol, and the community category to look in.
1 · Intake & pumping
Submersible pumps lift influent from the wet well into the headworks. Coarse screens remove solids upstream of the wet well.
- Submersible pumps — the symbol usually sits inside the wet-well outline; show run state plus level (the pumps are level-controlled, operators read both together)
- Self-priming pumps — dry-pit stations; same block as a centrifugal pump, the priming chamber is a detail you can skip on the overview
- Sump pumps — small, often drawn as a half-size pump block in a corner of the building view
- End-suction centrifugal — the workhorse for transfer duty; one symbol, reused everywhere, with the 9-state encoding below
Symbols: community pumps · search "submersible" · draw your own in the Symbol Builder
2 · Headworks (screening & grit removal)
Bar screens, screen rakes, grit chambers. Reduces wear on downstream equipment.
- Knife gates (manual / pneumatic / electric) — show open / closed / travelling and the actuator type; a manual gate without feedback should look different from a motorised one so nobody expects it to move from the screen
- Slide gates (rectangular, bulk solids) — for the grit and screenings chutes; same open/closed/fault logic
- Apron / bucket conveyors for grit removal — running direction arrow plus motor state; a stopped conveyor with material on it is a common alarm cause
Symbols: community gates · community conveyors · Symbol Builder
3 · Primary clarification
Settles solids by gravity. The skimmer mechanism rotates a sweeper blade across the surface and bottom.
- Drive motors with VFD — motor block with a speed or torque readout next to it; sweeper drives trip on torque, so put torque where the operator will see it
- Sludge transfer screw conveyors — screw symbol with direction; runs intermittently on a timer, so the "stopped" state is normal and should not read as a fault
Symbols: community motors · search "screw" · Symbol Builder
4 · Aeration / biological treatment
Diffused-air aeration in activated sludge plants. PD (positive-displacement) blowers feed the diffusers; dissolved-oxygen probes close the loop.
- Positive-displacement blowers — the canonical wastewater symbol is a blower with inlet/outlet silencers; show discharge pressure and temperature, both are trip causes
- Centrifugal / turbo blowers (high-efficiency) — same block, different internals; speed or guide-vane position is the useful readout
- Liquid-ring vacuum pumps — for degassing and priming; pump block, add the seal-water flow if it has a switch
- Reversible motors for clarifier sweepers and mixers — show FWD/REV inside the block so direction is readable at a glance
Symbols: community pumps & blowers · search "blower" · community motors · Symbol Builder
5 · Sludge dewatering
Concentrate biosolids before disposal. Belt presses and decanter centrifuges are the two mainstream technologies.
- Decanter centrifuges — bowl speed, differential speed and torque on the screen; the symbol itself is a horizontal bowl with conical end and two outlets (cake / centrate)
- Belt-press filters — belt speed and tension; a side view with two rollers and the belt reads well at small sizes
- Progressive cavity pumps for thickened sludge — dry-run protection matters here; show the pump with its inlet pressure or "no flow" interlock badge
- Polymer dosing / booster-pump skids — group pump + tank + flow meter inside one skid outline instead of drawing each separately
Symbols: search "centrifuge" · community process equipment · community pumps · Symbol Builder
6 · Odor control / scrubbers
Headworks and dewatering buildings need odor mitigation. Packed-bed scrubbers with caustic recirculation are common.
- Packed-bed scrubbers — vertical vessel with packing hatch, recirculation pump and fan; show recirculation flow and pH of the scrubbing liquor
- Cyclone separators — upstream of fans where dust or droplets are an issue
- Demister vessels — simple vessel with mesh pad; differential pressure is the one number worth showing
Symbols: search "scrubber" · community process equipment · Symbol Builder
7 · Disinfection & discharge
UV reactors, chlorine contact tanks, plus the effluent pumping station back to the receiving body.
- Chemical storage (hypochlorite, bullet tanks for chlorine gas where still in use) — tank with level; chemical tanks get a low-level alarm badge, not a color fill
- Multistage centrifugal pumps — effluent reuse / high-head duties; same pump block, pressure readout
- Inline vertical pumps — compact stations; a vertical variant of the pump block keeps the P&ID orientation recognisable
Symbols: community tanks · community pumps · Symbol Builder
Instrumentation (ISA-5.1)
Wastewater plants are instrumentation-heavy: flow on every line, level in every well, DO and pH in every basin. Instrument bubbles, connection lines and alarm badges are generic iconography and live in the official icon library; meter body symbols (Coriolis, magnetic, ultrasonic, rotameter) are equipment and come from the community or the Builder:
Flow meters
Magnetic (the wastewater default), ultrasonic, Coriolis for chemicals, rotameter, orifice
Icon libraryBubble shapes
Field, DCS, PLC, shared, logic — empty for tag overlay
Icon libraryAlarm badges
P1-P4, ESD trip, deviation, rate-of-change, predictive
Icon libraryConnection lines
Pipe, electrical, pneumatic, hydraulic, capillary, fieldbus
Recommended PLC architecture for wastewater
Most plants I have seen use the same encoding regardless of PLC brand, and it is what every symbol on this page assumes:
- 1 INT word per equipment, encoded 0-8 (Stopped → Fault). Maps directly to a Multi-state Lamp / Indicator / Image with no logic in the HMI.
- Alarm priorities aggregated from individual booleans into a single P1/P2/P3/P4 indicator on the screen.
- Operating mode separate from state: Manual / Auto / Local in a parallel BOOL set, displayed as a colored badge on the corner of the equipment block.
See the 9 motor states encoding for the full state table, and the integration guides for vendor-specific binding patterns. If you publish a pump or blower symbol, adding the 0-8 state as a tag in its description makes it easier for the next person to bind.
Why ISA-101 matters for wastewater operators
Wastewater control rooms see equipment counts in the hundreds: every lift station, every blower, every actuator. With a non-standard color palette, operators struggle to spot the one motor that just tripped among 300 visual elements.
ISA-101's calm gray background, color reserved for action philosophy is exactly what high-element-count plants need. A single red badge on a gray panel is unmissable; the same red on a saturated screen disappears. Read more in the calm HMI color palette guide.
Getting the symbols for a wastewater plant
Nothing to buy per industry: the equipment symbols come from other engineers or from you, and the generic iconography is in the icon library.
Explore published symbols
Pumps, blowers, gates, tanks, process units shared under CC BY 4.0. Download PNG/SVG, credit the author.
Symbol BuilderDraw the missing ones
Decanter, scrubber, knife gate — whatever isn't there yet. Free, in the browser. Publish it and it costs you nothing to download.
Icon libraryAlarms, bubbles, lines
Alarm badges, state badges, instrument bubbles, connection lines, arrows and indicators.
Downloads: Free account 5 a month · Starter 50 a month · Studio unlimited. Your own published symbols download free.
Stuck on a specific symbol or screen?
Ask in the forum — how to draw a belt press at 64 px, how to bind a 9-state word in Ignition, how other plants lay out a blower building. Questions with a screenshot get better answers.
Ask the community → Read import guides →Other industries
- Food & Beverage — CIP/SIP, fillers, mixers, conveyors, pasteurizers
- Mining & Bulk Solids — crushers, screens, ball mills, conveyors
- All industries →
Keep going
- Explore community symbols — browse by category: pumps, gates, motors, tanks, process, instrumentation
- Symbol Builder — draw and export PNG/SVG, publish under CC BY 4.0
- Generic icon library — alarm and state badges, instrument bubbles, connection lines, HMI navigation icons
- Community forum — questions about HMI design, standards and vendor tooling