Key Parameters and Online Monitoring Solutions for Papermaking Plant Wastewater Quality Monitoring Stations

I. Pollution Characteristics and Monitoring Logic of Papermaking Wastewater

Papermaking processes are divided into mechanical and handmade forms. Regardless of the type, high-concentration organic wastewater is generated during production. Typical papermaking wastewater contains lignin, cellulose, organic acids, pigments, and chemical additives, characterized by high COD concentration, deep color, and high suspended solids. If discharged directly without treatment, it will seriously pollute the receiving water body, causing a sharp drop in dissolved oxygen and ecological damage.

From an engineering perspective, the core task of papermaking plant wastewater monitoring is not single total control at the final discharge outlet, but deploying monitoring stations in layers at key workshop discharge outlets and the final discharge outlet according to the pollution source characteristics of different production sections, achieving dual control of source identification and end-of-pipe compliance.

II. Monitoring Station Layout Principles and Point Planning

The setting of papermaking plant wastewater monitoring stations needs to be determined according to the production process. The following are three types of typical monitoring points:

III. Key Parameters and Online Monitoring Solutions for Each Monitoring Point

3.1 Enterprise Final Discharge Outlet Monitoring Parameters

The final discharge outlet is the last checkpoint before all treated wastewater leaves the plant. Monitoring indicators need to cover comprehensive pollution levels. It is recommended to configure the following online monitoring parameters:

3.2 Elemental Chlorine Bleaching Workshop Discharge Outlet

Chlorine-containing bleaching processes produce adsorbable organic halogens (AOX), which include persistent organic pollutants such as dioxins and chlorophenols. The focus of monitoring at this point is:

3.3 Deinking Workshop Discharge Outlet

Deinking processes use surfactants, sodium hydroxide and complexing agents, which may introduce heavy metals (such as lead, chromium, cadmium). Monitoring at this point focuses on heavy metal indicators:

IV. Engineering Integration of NiuBoL Online Monitoring System

Papermaking plant wastewater monitoring points are scattered and working conditions are complex, requiring high standards for communication integration and protection levels of online monitoring equipment. NiuBoL provides the following engineering features:

FAQ

Q1: COD concentration in papermaking wastewater fluctuates greatly (500~5000 mg/L). Can online monitors adapt?

Yes. The NiuBoL NB-CODcr analyzer is equipped with full-range automatic switching function as standard, using the potassium dichromate method and high-temperature digestion at 165℃, with a response cycle of about 40 minutes. It is recommended to install a filtration device before the sampling point to prevent fibrous suspended solids from clogging the pipeline.

Q2: What is the maintenance cycle for AOX online monitoring equipment?

The activated carbon adsorption column of the NB-AOX analyzer is replaced every 30 days, and the combustion furnace catalyst is checked every 6 months. The equipment has a reagent remaining alarm function and can push maintenance reminders through the remote platform.

Q3: Does heavy metal monitoring at the deinking workshop discharge outlet require separate sample pretreatment?

Yes. Heavy metals in deinking wastewater partially exist in complexed states. The NiuBoL system integrates an ultraviolet digestion module, which automatically completes digestion before measurement, converting complexed heavy metals into free ions for detection.

Q4: How to uniformly connect equipment from multiple monitoring points to the central control system?

NiuBoL provides the NB-DTU data acquisition terminal, which supports 8-channel RS485 device convergence and uploads to the central control SCADA via Ethernet or 4G using Modbus TCP protocol. It also provides OPC UA interface, compatible with mainstream configuration software such as WinCC and KingView.

Q5: How to ensure accuracy of color monitoring at the final discharge outlet during decolorizing agent dosing fluctuations?

Using the platinum-cobalt colorimetric method (GB 11903), the NiuBoL NBL-Color has automatic zero-point calibration and bubble elimination functions. For extreme samples with color >500 times, the equipment can automatically dilute before measurement.

Q6: Papermaking wastewater contains large amounts of Ca²⁺ and SO₄²⁻. How is the pH electrode lifespan?

Ca²⁺ easily forms calcium sulfate scaling at the electrode liquid junction. The NiuBoL pH electrode adopts an open liquid junction and pressurized electrolyte system, combined with a weekly automatic acid washing program, with a typical lifespan of 12~18 months in papermaking wastewater.

 Water Quality Sensor Data Sheet

NBL-WQ-CL Water Quality Sensor Online Residual Chlorine Sensor.pdf

NBL-WQ-DO Online Fluorescence Dissolved Oxygen Sensor.pdf

NBL-WQ-NHN Ammonia Nitrogen Water Quality Sensor.pdf

NBL-WQ-COD Online Water Quality COD Sensor.pdf

NBL-WQ-PH Online pH Water Quality Sensor.pdf

NBL-WQ-EC water quality conductivity sensor.pdf

NBL-WQ-BOD-4A Online BOD Sensor.pdf