"The Pulse Monitor" of Water Treatment: The Indispensable Flowmeter

In the vast and intricate "city" of water treatment, various equipment performs its own duties, working together to ensure the safe transformation from raw water to clean water, and from wastewater to purified water. If water pumps are the heart and pipelines are the blood vessels, then flowmeters are the "pulse monitors"遍布全身 (found throughout the system). They continuously and accurately measure the "heartbeat" of water flow—the flow rate—providing the most fundamental and critical data support for process control, cost accounting, and environmental protection.

So, where exactly are flowmeters needed in the various stages of water treatment? We can follow the journey of water to find out.

I. Source Control: Water Intake and Inflow Stages
Raw water intake points: Whether drawing water from rivers, lakes, or reservoirs, flowmeters must be installed on the outlet pipelines of the intake pumping stations. The purposes are:

Measuring total water intake: This is the core basis for settlements between water plants and water source management units, as well as fundamental data for统计区域用水总量 (calculating regional total water usage).

Controlling pump operation: Flow data can optimize the start-stop and speed regulation of pumps, achieving energy savings and consumption reduction.

Water plant/wastewater plant inlet: The first gateway where water enters the treatment plant. Here, flowmeters act as "sentries."

Basis for process control: The inflow rate is the baseline value for adjusting all subsequent treatment process parameters (such as chemical dosing, aeration volume, and sludge discharge). Knowing "how much water is coming in" determines "how much chemical to add."

Load warning: Excessively high instantaneous flow rates (e.g., during heavy rain) can shock the treatment system. Flowmeters can provide timely warnings, helping operators prepare in advance.

II. Precision in Process: Core Treatment and Dosing Stages
This is where flowmeters are most widely used and where requirements are most meticulous, directly impacting treatment effectiveness, operational stability, and cost control.

Chemical dosing: Water treatment requires the addition of chemicals such as coagulants, flocculants, disinfectants (e.g., chlorine), and acids/bases (for pH adjustment). The dosage of these chemicals must be precisely proportional to the inflow rate.

Ratio control: The signal from the flowmeter is transmitted to the dosing pump (metering pump), enabling "dosing according to flow." This ensures treatment effectiveness (avoiding under-dosing) and prevents waste and secondary pollution (avoiding over-dosing). This stage typically uses high-precision electromagnetic or mass flowmeters.

Sludge treatment line:

Sludge return: Returning activated sludge from the bottom of the sedimentation tank to the front end of the biological tank is crucial for maintaining microbial concentration. Flowmeters are needed to control the return ratio and ensure the biological system remains stable and efficient.

Excess sludge discharge: Periodically discharging excess sludge proliferated within the system requires flowmeters to precisely control the discharge amount, avoiding impacts on system balance from over- or under-discharging.

Sludge conveyance and dewatering: Flowmeters are needed before and after sludge enters dewatering equipment (e.g., centrifuges, belt filter presses) to monitor progress and calculate production.

Aeration process control: In biological treatment units (e.g., AAO, oxidation ditches), the amount of air or oxygen pumped into the wastewater is critical.

Air flowmeters: Installed on the outlet pipeline of blowers or aeration branch pipes, gas flowmeters are used to monitor aeration intensity, optimize energy consumption (aeration is one of the largest energy-consuming units in a plant), and ensure microorganisms have sufficient oxygen for degradation reactions.

Filtration and backwashing:

Filter effluent: Monitoring the effluent flow rate of each filter to assess its operational status and performance.

Backwash water: Filters periodically require backwashing with clean water or an air-water mixture to restore filtration capacity. Flowmeters are used to control the intensity and duration of backwashing, preventing inadequate cleaning or water waste.

III. End Monitoring: Effluent and Distribution Stages
Treatment plant final effluent outlet: This is a mandatory installation point required by regulations, the "final report card" of the water treatment process.

Compliance discharge accounting: Environmental authorities calculate total pollutant discharge based on effluent flow rate and pollutant concentrations (e.g., COD, ammonia nitrogen). This is key data for environmental(monitoring and charging).

Performance evaluation: Statistics on the plant's daily actual treated water volume are important indicators for assessing operational efficiency and treatment capacity.

Reclaimed water (recycled water) reuse: For reclaimed water supplied to users (e.g., for landscaping, flushing, industrial cooling) after advanced treatment, flowmeters are needed for trade settlement and usage monitoring.

Clean water transmission and network distribution: In municipal water supply networks, flowmeters are widely installed at booster pumping stations, district metered areas (DMA), and large user inlets.

Network balance and leakage control: By comparing inflow and outflow rates in different areas, pipeline leaks can be quickly located and assessed, reducing non-revenue water.

Water supply (dispatching): Based on real-time flow changes, pump and plant capacity can be scientifically dispatched to ensure stable water supply pressure.

How to Choose the Right Flowmeter?
Requirements for flowmeters vary across different stages. Main considerations include:

Medium type: Is it clean water, wastewater, sludge, or chemicals? What is its corrosiveness and conductivity?

Accuracy requirements: Is it for trade settlement (high accuracy) or process control (medium accuracy)?

Pipe diameter and flow range: Is it large diameter with low flow velocity, or small diameter with high flow velocity?

Installation conditions: Is there sufficient straight pipe length? Is the pipe full or partially full?

Common types of flowmeters include electromagnetic flowmeters (preferred for conductive liquids), ultrasonic flowmeters (convenient for pressurized installation), vortex flowmeters (for clean gases/liquids), mass flowmeters (for high-precision chemical measurement), and open channel flowmeters (for plant drainage channels).

Conclusion
In summary, from the inflow of a drop of raw water to the outflow of a drop of clean water, the presence of flowmeters permeates the entire lifecycle of water treatment. They are the "eyes" of production, the "scale" for costs, and the "ruler" for environmental protection. In the era of smart water and精细化管理 (refined management), accurate and reliable flow data has become increasingly important, continuously providing the most powerful data pulse for the efficient, economical, and stable operation of this "city of water."