Automatic control system for sewage treatment

With the continuous development of science and technology, the application of automation technology in sewage treatment systems will make sewage treatment efficiency higher, reliability stronger, and water quality more stable. Research on the specific direction of automatic control system transformation based on existing sewage treatment technologies.

1. The composition of the automatic control system.

The automatic control system of the sewage treatment plant mainly consists of a power distribution part, a PLC control part, and cables as its main facilities. The power distribution part is responsible for supplying power to all process equipment and automatic control systems, and running relevant instructions transmitted by the control system to control the start and stop of process equipment; The PLC control part consists of PLC modules, control system power supply, various online detection instruments or sensors, and industrial control computers, becoming the focus of the automatic control system of the sewage treatment plant.

2. Equipment required for automatic control system.

When designing a coal mine sewage treatment system, the selection of equipment types must be based on equipment performance, equipment cost, as well as the environmental humidity of the sewage treatment station. On the basis of meeting the needs of environmental development, products with relatively high cost-effectiveness should be selected.

(1) Power distribution cabinet: The power consumption is a secondary load, and the low-voltage side adopts a radial distribution method.

(2) Cable: YJV-0.6/1KV was selected for the power cable, and KVV-0.45/0.75KV was selected for the control cable.

(3) Grounding system: TN-C-S system is adopted, and the power line to the distribution cabinet adopts a 5-core cable. The neutral line N and the protective line PE are separated, and the grounding resistance is not greater than 4 Ω.

3. Equipment automatic control design.

(1) The control method of the equipment.

① On site manual mode:

When the "manual/automatic" switch on the on-site control box or control cabinet of the equipment is selected as the "manual" mode, the equipment can be started/stopped and turned on/off through the buttons on the on-site control box or control cabinet.

② Automatic mode:

The "manual/automatic" switch on the on-site control box or cabinet selects the "automatic" mode, and the operation of the equipment is completely controlled by the on-site control station according to the working conditions and production requirements of the sewage treatment plant to control the operation or on/off of the equipment.

(2) Main process control.

① Fine grille: In general, the operation of the fine grille is regulated by the water level in front of the grille, running at high water levels and stopping at low water levels.

② Primary lift pump. The operation of the first level lifting pump adopts water level control. The control cabinet automatically controls the number of running water pumps according to the water level in the regulating pool. It runs at high water level and stops at low water level, and automatically rotates to participate in the operation according to the running time of each water pump, so that the running time of each water pump is equal. In addition, an ultra-high liquid level alarm is installed in the regulating pool. After the alarm lasts for 10 seconds, two pumps can be started simultaneously. The system also has dry operation protection to extend the service life of the water pump.

③ Sludge thickening tank. The reflux of clear liquid on the sludge concentration tank is controlled by an electric valve, and the opening and closing of the electric valve is controlled by the liquid level controller to adjust the liquid level. Two methods are adopted: on-site manual control and PLC control.

④ Adjust the tank mixer. The device is equipped with automatic control and manual control buttons installed on site. The control room can display the real-time operation status of the mixer.

⑤ Secondary lift pump. The operation of the secondary lift pump adopts water level control. The control cabinet automatically controls the number of water pumps based on the water level in the intermediate pool. It operates at high water levels and stops at low water levels, and automatically rotates to participate in the operation according to the running time of each water pump, so that the running time of each water pump is equal. In addition, an ultra-high liquid level alarm is installed in the intermediate pool.

⑥ The dosing pump of the dosing system accurately measures the dosage of the medication, and the mixing device of the dosing system can be timed or manually adjusted for opening time and operation mode, controlled and managed by the PLC control station.