Today we're looking at the important topic of wastewater treatment and the role that precipitants play in this. When it comes to the chemical treatment of wastewater in precipitation plants, it is crucial to choose the right precipitant to ensure effective treatment.
In this article, we will give you useful tips and recommendations for choosing the right precipitant for your specific requirements. Learn more about the different types of precipitants, the areas of application, the factors that influence efficiency and best practices when using precipitants.
Table of contents
Importance of precipitants in wastewater treatment
The selection and dosing of the optimum precipitant is an essential aspect of wastewater treatment, especially in the treatment of wastewater from the non-food sector. These agents play an important role in the removal of heavy metals, phosphates or hydrocarbons from wastewater, for example.
One of the biggest challenges in wastewater treatment is the complexity and diversity of contaminants. Precipitants help to make wastewater treatment more effective by specifically precipitating the pollutants and thus facilitating their removal. However, their use requires careful dosing and control.
As a specialist in industrial wastewater treatment, we have the necessary expertise to support our customers in the selection of suitable precipitants and in monitoring the treatment process.
What are precipitants?
Definition and function of precipitants
Precipitants are chemical substances that are added to wastewater to convert dissolved compounds into undissolved particulate substances. In contrast to dissolved substances, these undissolved substances can be separated by simple physical processes such as sedimentation or flotation.
The dosage and use of precipitants depend on the type of contamination and the legal requirements for wastewater treatment. Careful monitoring and control of the cleaning process is therefore essential.
Types of precipitants
There are different types of precipitants that are used in wastewater treatment. The majority of wastewater applications are covered by three types of precipitants. They are either based on iron salts, aluminum salts or belong to the sulfidic precipitants.
The advantage of aluminum-based precipitants is that they have a low specific molecular weight. This is a particularly important influencing factor when using precipitants in dissolved air flotation. The lower the specific weight of the resulting sludge flocs, the easier the flotation of the sludge flocs. The most commonly used precipitants based on aluminum-containing compounds are Polyaluminum hydroxide chloride, dialuminum chloride pentahydroxide and aluminum sulfate.
Iron-based precipitants, in particular iron(III) chloride, are probably the most commonly used precipitants. Due to the high binding affinity of trivalent iron to trivalent phosphates, the precipitant is often used for phosphate elimination, e.g. in municipal sewage treatment plants.
Precipitants based on aluminium or iron salts are used in combination with neutralizing agents. These neutralizing agents shift the pH value of the wastewater due to their hydroxide group. Accordingly, this is referred to as hydroxide precipitation or neutralization precipitation.
These types of felling reach their limits when:
- very low limit values must be achieved,
- a high concentration of complexing agents is present in the wastewater, or
- compounds are present in the wastewater that cannot be precipitated by hydroxide precipitation.
For these tasks, so-called sulphidic precipitation is carried out downstream of hydroxide precipitation. As the name suggests, precipitants based on sulphur compounds are used for this. The most commonly used sulphide precipitants are sodium sulphide and organosulphide. With the combination of hydroxide and sulphide precipitation, purification performance of > 99 % can often be achieved.
Photo: ALMAFloc APH (to the product) Combination product of precipitant, flocculant and neutralizing agent
Selecting the right precipitant
Analysis of wastewater samples
Selecting the right precipitant is crucial for effective industrial wastewater treatment. To select the right precipitant, wastewater samples must first be analyzed. The analysis can determine the type and concentration of impurities present in the wastewater.
The analysis of the wastewater samples provides information on which precipitant is best suited to remove the specific impurities. An incorrect choice of precipitant can lead to ineffective cleaning, as not all impurities can be removed.
Our experienced team of experts in industrial wastewater treatment specializes in analysing wastewater samples and selecting the right precipitant. We take into account not only the type of contamination, but also the legal requirements and the specific needs of our customers.
By selecting the right precipitant and carefully monitoring the cleaning process, we can ensure that our customer receives effective and environmentally friendly wastewater treatment.
Advice from experts
Choosing the right precipitant is crucial for effective industrial wastewater treatment. Our experienced experts will be happy to advise you on choosing the right precipitant for your specific needs. Contact us for advice on the optimal choice of chemicals and send us a wastewater sample to be analyzed in our laboratory.
Factors that influence the efficiency of precipitants
pH value of the wastewater
The pH value of wastewater is one of the most important factors influencing the efficiency of precipitants in industrial wastewater treatment. The pH value is a measure of the concentration of hydrogen ions in the wastewater and can be measured on a scale from 0 to 14. A pH value of 7 is neutral, values below 7 are acidic and values above 7 are alkaline.
The precipitation process is based on the chemical reaction of precipitants with dissolved pollutants in the wastewater. This results in the formation of insoluble substances, so-called flocs, which can then be separated. The pH value influences these reactions in various ways. If the pH value is too high or too low, this can impair or even prevent the formation of flocs. An environment that is too acidic or too alkaline can severely impair the effect of precipitants.
To ensure that the precipitant works optimally, the pH value of the wastewater must therefore be carefully monitored and regulated. It is important that the pH value is kept within the optimum range for the precipitant in question. By choosing the right precipitant and monitoring the pH value, companies can ensure effective and efficient industrial wastewater treatment.
Concentration of dissolved substances
The concentration of dissolved substances in wastewater is an important factor that influences the efficiency of precipitants in industrial wastewater treatment. If the concentration of pollutants in the wastewater is too high, this can impair the effectiveness of precipitants.
The precipitation process is based on the chemical reaction of precipitants with the dissolved pollutants in the wastewater. This results in the formation of flocs, which can then be separated. If the concentration of pollutants in the wastewater is too high, this can impair or prevent the formation of flocs. In this case, it may be necessary to use higher doses of precipitants to ensure sufficient removal of the pollutants.
On the other hand, too low a concentration of pollutants in the wastewater can also impair the effectiveness of precipitants. In this case, the precipitants cannot react effectively with the pollutants in the wastewater and the formation of flocs is prevented.
It is therefore important that the concentration of pollutants in the wastewater is carefully monitored and regulated to ensure that the precipitants can work effectively.
Temperature of the waste water
precipitants in wastewater treatment. As a rule, precipitants work more effectively at higher temperatures than at lower temperatures. This is because the chemical reactions between the precipitants and the substances contained in the wastewater can take place faster and more effectively at higher temperatures.
However, if the wastewater is too hot, this can also lead to problems. A pH value that is too high and a temperature that is too high can cause precipitants to become inactive or not function properly. In addition, too high a temperature can shorten the life of precipitants and increase the risk of blockages in pipes and lines.
Best practices in the use of precipitants
Correct dosage
Precipitants are an indispensable component of wastewater treatment in industry. It is important that the precipitant is used in the correct dosage to ensure efficient wastewater treatment. Overdosing leads to unnecessary costs and can even cause damage to the systems. Underdosing, on the other hand, can limit the effectiveness of the precipitant.
The dosage of precipitants depends on various factors, such as the type of wastewater, the concentration of dissolved substances and the desired degree of purification. It is therefore advisable to analyze wastewater samples to determine the optimum dosage.
In order to achieve optimum dosing, it is also important to introduce the precipitant evenly and continuously into the wastewater. Special dosing equipment can be used for this purpose.
Here you will find an overview of our dosing stations for precipitants, neutralizing agents and flocculants.
Avoidance of overdosing
The correct dosage of precipitants is crucial for effective wastewater treatment. To avoid overdosing, the wastewater should be thoroughly analyzed before precipitants are added. In this way, the dosage can be precisely determined to ensure the desired floc formation and the required removal of pollutants.
Another important factor in avoiding overdosing is monitoring the wastewater flow and the additives. It is important to continuously monitor the amount of precipitants added and adjust accordingly to avoid overdosing.
Overdosing of precipitants can not only lead to increased costs, but also to undesirable effects on wastewater treatment and the environment. To avoid this, operators of wastewater treatment plants should regularly train their employees and ensure compliance with best practices in the use of precipitants.
Conclusion
The selection and use of the right precipitant is crucial for the effective treatment of industrial wastewater. Here are some recommendations that should be considered when selecting and using precipitants:
- Analysis of wastewater samples: Before selecting a precipitant, a thorough analysis of the wastewater samples should be carried out to determine the type and concentration of the substances to be removed.
- Dosage: Precipitants should be dosed in accordance with the manufacturer's instructions. Overdosing can lead to problems such as sludge deposits, while underdosing impairs the effectiveness of cleaning.
- Avoiding overdosing: To avoid overdosing, the dosage should be increased gradually until the optimum quantity is reached. The amount of precipitant should also be adjusted to the fluctuations in the waste water.
- Monitoring: It is important to monitor the cleaning process regularly to ensure that the precipitant is working properly and achieving the desired results.
- Disposal: Disposal of residues after cleaning should be carried out in accordance with environmental regulations.
By taking these recommendations into account, you can ensure that you select the best precipitant for your requirements and make the best use of it. If you need help with the selection or application of precipitants, contact our experts and let us carry out laboratory tests with your wastewater to determine the optimum precipitant.
