Huangshan City Wastewater Treatment Plant Case

Huangshan City, Anhui Province, is investing in the construction of a sewage treatment plant. The first phase of the project, with a daily treatment capacity of 15,000 m³, has been completed and plays a crucial role in purifying both domestic and industrial wastewater.

During the sewage treatment process, measuring the raw sewage flow rate is a key parameter. Since raw sewage contains particles, suspended solids, and a mixture of liquid and solid components with corrosive properties, electromagnetic flow meters are an ideal choice. Their key advantage is the ability to measure the flow of acidic, alkaline, and saline solutions, as well as liquids containing solid particles (such as sludge) or fibrous materials. Therefore, this sewage treatment plant has installed six electromagnetic flow meters for raw sewage flow measurement.

Challenges:

1. Large-diameter pipelines and cost considerations acceptable to the customer.

2. The measured liquid is corrosive and contains particles of various sizes, requiring careful selection of wear-resistant materials. Additionally, the liquid’s high temperature must be considered.

Selection of Electromagnetic Flow Meters for Sewage Treatment:

1. Diameter Selection

Based on the process pipeline diameter, pipeline pressure, and sewage flow rate provided by the sewage treatment plant, a DN600mm electromagnetic flow meter was selected. No pipeline reduction or expansion is needed on-site.

2. Lining and Electrode Material Selection

Lining materials for electromagnetic flow meters include:

• Neoprene (Chloroprene Rubber): Moderate corrosion resistance, suitable for low-concentration acid, alkali, and saline solutions.

• Polyurethane Rubber: Strong wear resistance but moderate corrosion resistance.

• PTFE (Polytetrafluoroethylene): Excellent corrosion resistance, suitable for high-temperature environments.

• FEP (Perfluoroalkoxy): Chemically similar to PTFE, with good tensile and compressive strength.

• Polyethylene (PE): Resistant to dilute acids, alkalis, and salts, suitable for temperatures below 60°C.

• Polyphenylene Sulfide (PPS): Suitable for temperatures below 100°C, with good corrosion resistance.

Electrode materials must be selected based on the corrosion properties of the measured liquid:

• Titanium (Ti): Resistant to salt and alkaline solutions with concentrations below 50%.

• Tantalum (Ta): Resistant to acids and salts.

• Platinum (Pt): Highly corrosion-resistant noble metal.

• Hastelloy C: Suitable for most corrosive media but not hydrochloric acid.

• Hastelloy B: Suitable for some acidic environments but not nitric acid.

• 316L Stainless Steel: Moderate corrosion resistance but cost-effective.

Considering that the sewage treatment plant primarily processes domestic and industrial wastewater while also taking cost considerations into account, neoprene lining and 316L stainless steel electrodes were selected.

3. Sensor Protection Level Selection

Electromagnetic flow meter sensors are available in two protection levels: IP65 (splash-proof) and IP68 (submersible-proof). Since the installation site is in a low underground well, the IP68 dustproof and submersible type was chosen. For sensors installed below ground, a remote-type (split-type) flow meter should be used.

4. Output and Communication Functions

The selected electromagnetic flow meter comes with an LCD display, 4–20mA current output, and 0–1KHz frequency output. To meet communication requirements with the computer system, an RS-485 communication interface is required.

Electromagnetic flowmeter for sewage treatment

Split-type Electromagnetic flowmeter for sewage

Final Selection

Based on the operating conditions of the sewage treatment plant, six DN600mm remote-type electromagnetic flow meters from our company were selected for flow measurement.