Pump Selection for Water Treatment Plants

Map Every Pump Duty in the Plant First

A water treatment plant is a sequence of hydraulic steps, each with a different fluid: raw water lifted from the intake, coagulants dosed, filter feed and backwash delivered, clarified water transferred and distributed, and solids leaving as sludge. List every duty — flow range, head, temperature, chemistry, solids content — before choosing any pump, as in our overview of water treatment pump selection.

• Raw water intake — clean, cold water at variable river or well levels.
• Chemical dosing — small, accurate coagulant and disinfectant metering.
• Filter feed and backwash — larger flows at moderate head, with backwash surges.
• Transfer and distribution — steady clean-water pumping to storage and the network.
• Sludge handling — viscous, solids-laden flows to thickeners and dewatering.

Clean-Water Stages: IS/ISW End-Suction Centrifugal Pumps

The backbone of a plant is the end-suction centrifugal pump: simple, efficient on clean water and available across the full flow range. Qingdao Green Power publishes the IS/ISW series for water and low-viscosity duty at 1.5–1600 m³/h flow, 2–125 m head and up to 80 °C, with motors from 0.18 kW to 250 kW. Above roughly 150 cSt a centrifugal loses efficiency fast, so keep the family on clean-water stages — intake, settled and clarified water, filter feed. Full details are on the industrial centrifugal pump page.

Space-Saving and Higher-Head Duties: ISG/GDL Inline Pumps

Where floor space is tight or head climbs — filter feed to elevated tanks, membrane feed, distribution boosting — a vertical inline pump installs directly in the pipe run with suction and discharge flanges in line. Qingdao Green Power's ISG/GDL pipeline pump range is published at 1.6–1200 m³/h flow, 5–150 m head and -20 °C to 120 °C; the GDL multistage variant covers the higher-head band above 80 m typical of backwash and booster duties.

Below-Grade Pits, Tanks and Wet Wells: ZJL/LZ Submerged Pumps

Not every suction source sits above the pump. Intake sumps, wash-water recovery pits and sludge holding tanks are often below grade, where a surface pump would need costly deep suction piping. A submerged vertical pump puts the impeller under the liquid: the motor stays above on a flanged top plate and the shaft runs down through a bearing column, so no mechanical seal sits in the liquid. Qingdao Green Power publishes the ZJL/LZ range at 2–600 m³/h flow, 8–100 m head and 0.5–3 m immersion (customisable), standard service to 100 °C and a high-temperature version to 300 °C — see the submerged vertical pump range for pit installations.

Sludge and Biosolids: G-Type Progressive Cavity Pumps

Solids removed by sedimentation and filtration leave as sludge — viscous, abrasive and often sticky — and centrifugal pumps are the wrong tool once it thickens. Sludge lines use a positive displacement machine, typically a G-type single-screw (progressive cavity) pump whose helical metal rotor turns inside an elastomeric stator; the sealed cavities travel from suction to discharge and push the sludge steadily at low shear. Qingdao Green Power publishes the G-type range at 0.1–150 m³/h flow and 0.6–2.4 MPa, with NBR, EPDM or FKM stators matched to the sludge. One rule is absolute: never run a progressive cavity pump dry — the elastomer stator is destroyed within seconds. Our article on the industrial sludge transfer pump covers stator and sizing practice.

The Wastewater Side of the Fence

Plants that also treat effluent face the mirror-image problem: raw sewage and solids-laden streams at the inlet. Qingdao Green Power covers that side with the ZW solids-handling centrifugal pump at 5–800 m³/h flow, 14–80 m head and 2.2–55 kW, its impeller passage matched to the debris. Where the two sides meet, balance capacities so no stage becomes a bottleneck; see our review of wastewater pump solutions.

Size the Duty, Then Confirm the Model

Close every stage the same way: size each pump on its worst operating point, keep available NPSH above the pump's requirement at the highest liquid temperature, and check materials and seals against the real chemistry — wetted parts that suit raw river water may not suit a chlorinated or coagulant-laden stream. Treatment plants run continuously, so efficiency and redundancy matter as much as first cost: stage pumps in parallel for turndown, add standby where the process cannot stop, and use variable-speed drives on swinging loads. The same duty-point discipline applies in industrial pumps in power plants. Send your stage-by-stage duty data to Qingdao Green Power and confirm current model availability and specifications before procurement.

Frequently Asked Questions