Technical specifications and implementation points for installation of water quality testing stations

1、 Preliminary survey and site selection planning

1. Survey the characteristics of the target water area

Use GPS positioning system combined with terrain surveying to accurately mark the installation location. For river type monitoring points, it is necessary to measure water depth, flow velocity, and channel width. Priority should be given to selecting straight sections with stable water flow, avoiding turbulent and return water areas. Lake type stations should ensure that the monitoring point is at least 5 meters away from the shoreline and the water depth is not less than 1.5 meters. The marine environment needs to assess the magnitude of tidal changes and select areas that are less affected by waves.

2. Investigation of environmental interference sources

Establish a list of pollution sources within a radius of 50 meters, indicating industrial discharge outlets, agricultural non-point source pollution areas, and shipping intensive areas. A portable multi parameter water quality meter is used for 72 hour continuous monitoring, recording the pH fluctuation range, dissolved oxygen diurnal variation curve, and abnormal peak conductivity to ensure that the site meets the requirements of the "Technical Specification for Surface Water Environmental Quality Monitoring".

2、 Infrastructure construction standards

1. Construction of fixed station buildings

The concrete foundation is poured with C30 commercial concrete, with a foundation size of 2.5m × 2.5m × 1.8m (length × width × depth), and reinforcement spacing of 200mm arranged in a double layered bidirectional manner. The walls of the station building are constructed with 240mm thick insulation bricks, and the interior walls are coated with waterproof putty and installed with polyurethane insulation boards. The roof is equipped with a 15 ° slope drainage structure. The lightning protection grounding system adopts Φ 12mm hot-dip galvanized round steel with a grounding resistance of ≤ 4 Ω.

2. Assembly of buoy platform

The diameter of HDPE floating body shall not be less than 1.2m, and the closed foam filler shall be filled inside, and the draft shall be controlled within 0.6-0.8m. The anchor chain system adopts 316L stainless steel float counterweight blocks, and the length of the main anchor chain is configured in a 1:1.5 ratio according to the water depth, with additional lateral stabilizing anchor chains forming a 120 ° angle. The installation height of navigation beacon lights should exceed the maximum water level by 0.5 meters and be equipped with radar reflectors and GPS positioning devices.

3、 Core equipment installation specifications

1. Multi parameter sensor array

The installation angle of the turbidity sensor should be kept at a 45 ° angle to the direction of the water flow, with a distance of 0.3-0.5 meters from the water surface. The working voltage of the dissolved oxygen probe is set to 0.6-0.8V polarization voltage, and the electrolyte of the membrane head is changed every week. The nutrient analyzer adopts a series flow tank design, with a water sample flow rate controlled at 200ml/min and a pressure threshold of 0.03MPa for the bubble removal device.

2. Automatic water collection system

The peristaltic pump tube is made of food grade silicone material and calibrated to 15 revolutions per minute. The sampling bottle is made of brown glass material, and the inner wall is treated with silane to reduce adsorption. The refrigeration unit is set at a temperature of 4 ± 0.5 ℃, and the temperature difference between the start and stop of the compressor is controlled at 2 ℃. Add ethylene glycol solution to the antifreeze circulation system to lower the freezing point to -20 ℃.

4、 Deployment of Electrical and Data Systems

1. Construction of power supply network

The inclination angle of the solar panel is equal to the local latitude plus 5 degrees, and the power calculation needs to meet the daily electricity consumption multiplied by a safety factor of 1.3. Lead acid battery pack capacity ≥ 3 days of rainy weather usage, equipped with explosion-proof box and temperature compensation charging controller. When connecting to the mains power supply, isolation transformers and surge protectors need to be installed, and the grounding bar is treated with tin plating on copper bars.

2. Data transmission link

The RS485 bus terminal resistor is matched with a 120 Ω precision resistor, and the Modbus protocol baud rate is fixed at 9600bps. Set up VPN private network transmission on 4G router, with heartbeat packet interval ≤ 30 seconds. The satellite terminal uses BGAN frequency band, with an antenna elevation angle error of less than 1 ° and a reserved 2dB rain attenuation margin.

5、 Debugging and acceptance standards

1. Sensor calibration process

The pH electrode adopts a three-point calibration method (pH 4.01/6.86/9.18 buffer solution), with a slope deviation of ≤ 1mV/pH. The conductivity standard solution was selected for two-stage verification of 1413 μ S/cm and 12.88mS/cm, with a nonlinear error of less than 0.5%. The turbidity NTU value was compared using a standard solution of fumarate, with an indication error of ± 2% FS.

2. System integration testing

The success rate of data continuation after simulating power outage recovery is 100%, and the completeness rate of historical data supplementation is ≥ 99%. The rainstorm condition test requires that the response time of the water level over limit alarm is less than 3 seconds, and the action error of the mechanical protection device is ± 5 cm. MTBF8000 hours of continuous 72 hour operation assessment.

6、 Operation and maintenance guarantee mechanism

Establish a three-level maintenance system: daily inspections (weekly) focus on checking cable sealing and sensor cleanliness; Quarterly maintenance includes mechanical lubrication and battery charging and discharging tests; Annual overhaul updates vulnerable parts and recalibrates measuring instruments. Biological pollution prevention and control is achieved through intermittent flushing with sodium hypochlorite, while algae growth inhibition is achieved through copper based anti fouling coatings. The special weather warning system is connected to the data interface of the meteorological bureau and the protection program is activated 6 hours in advance.