The inflow values describe the characteristic physical, chemical and biological parameters of water or wastewater that is fed into a water treatment plant. They are crucial for the design, control and monitoring of water and wastewater treatment processes. In contrast to the influent load, which describes the quantity of a substance over time, influent values indicate the concentration or property of a substance in the influent.
Determining and monitoring the feed values is essential in order to ensure stable process control, comply with legal discharge limits and minimize operating costs through targeted process optimization.
Table of contents
Definition and types of inlet values
Inlet values can be divided into different categories, depending on the characteristics of the wastewater or the requirements of the treatment plant.
1. physical inlet values
- Temperature: Crucial for biological processes and the solubility of gases.
- Turbidity: Indicates the content of suspended particles in the water.
- Conductivity: A measure of the salt content and the concentration of dissolved ions.
2. chemical feed values
- COD (chemical oxygen demand): Measures the total organic load in wastewater.
- BOD₅ (biochemical oxygen demand): Indicator for biodegradable organic substances.
- pH value: Important parameter for chemical reactions and biological treatment.
- Nutrients: concentrations of nitrogen (ammonium, nitrate) and phosphate.
- Heavy metals: concentrations of zinc, nickel, copper or chromium.
3. biological inflow values
- Microbiological contamination: bacterial counts and biological activity, e.g. in raw water or wastewater with organic contamination.
Significance of the inflow values
Dimensioning and design of treatment plants
The feed values are the basic data on which the design of a system is based. They determine the capacity and type of process stages required.
- Biological processes: The COD and BOD₅ value in the feed defines the required biomass and oxygen supply or the reactor size of anaerobic biogas plants.
- Chemical-physical processes: Heavy metal or phosphate concentrations influence the dosing of precipitants in CP systems.
- Membrane processes: The conductivity, salt content and turbidity determine the requirements for membrane systems such as ultrafiltration or reverse osmosis.
Process monitoring and control
Continuous monitoring of the feed values enables effective process control:
- pH value: Regulation of neutralization before biological or chemical processes.
- COD value: Adjustment of aeration and biomass in activated sludge plants.
- Heavy metal content: Optimization of the dosing of precipitants.
Compliance with legal requirements
The inlet values must be matched to the capacity of the system in order to ensure compliance with the legal discharge limits for the treated water. High inflow values can cause the system to be overloaded and the limit values to be exceeded.
Photo: Our anaerobic biogas reactor ALMA BHU GMR: The dimensioning and design of the reactor are based on the feed load in order to ensure optimum biogas production and process stability.
Typical fluctuations and challenges
Fluctuations in the inflow values
In industrial wastewater technology, inflow values are often subject to strong fluctuations due to:
- Production processes: Changing operating steps or batch processes.
- Rinsing and cleaning cycles: Sudden peaks in organic substances, chemicals or heavy metals.
- Mixed wastewater: Wastewater from different sources with varying loads.
Strategies for stabilization
Buffer systems or homogenization tanks are used to compensate for fluctuations:
- Volume compensation: Reduction of hydraulic peaks.
- Concentration equalization: Homogenization of the material load through continuous mixing.
Examples of applications
1. chemical-physical treatment
- Heavy metal concentrations in the feed of the CP system control the dosing of precipitants such as iron or aluminum salts.
- pH value: Neutralization is controlled with acids or alkalis based on the feed values.
2. biological wastewater treatment
- COD and BOD₅ values in the influent determine the oxygen supply and sludge concentration in biological reactors.
- Ammonium and nitrate values influence the need for nitrification and denitrification processes.
3. membrane process
- Turbidity, conductivity and salt concentration in the feed define the pre-treatment to prevent scaling and fouling on the membrane system and to calculate the required membrane area and pump pressures.
Photo: Our ALMA OSMO reverse osmosis system: The precise calculation of the required membrane surface area is largely based on the feed loads to ensure optimum performance and efficiency.
Measurement and monitoring of the inlet values
The inflow values are monitored using online measurement technology or manual sampling. Typical measuring devices and methods:
- Online sensors: For pH value, COD, conductivity and temperature.
- Spectroscopic analyses: For the determination of organic compounds (e.g. TOC).
- Laboratory analyses: For heavy metals and nutrients.
Conclusion
The inflow values are a key parameter in industrial water and wastewater treatment. They determine the design and operation of treatment plants and are essential for compliance with legal requirements. However, fluctuations in the feed values pose a major challenge and require the use of modern control systems and buffering devices.
Precise monitoring and control of the feed values not only enables efficient and stable process control, but also helps to optimize operating costs and protect the environment.
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