Donau PAC AQUACLEAR: Successful field test for the removal of micropollutants from wastewater

As already indicated in my blog post "Micropollutants in wastewater: Difficult to measure but nevertheless not without impact!", Donau Chemie AG's water technology department has been working on the removal of micropollutants from water for quite some time. The result of this work is Donau PAC AQUACLEAR, a powdered activated carbon (PAC) enhanced by combination with precipitants, which can be applied without costly changes to plant or processes, thus at medium-sized and small wastewater treatment plants.

In summer 2021, we kindly asked the Institute of Water Quality and Resource Management at the TU Wien (Technical University of Vienna) to test Donau PAC AQUACLEAR in a field trial. The entirely positive results of this study can now be reviewed in the current issue of ÖWAW.

Although I enjoyed reading the report very much, I found that my practically oriented colleagues in particular were very little interested in the scientific details of the study. They were looking for short and clear statements on whether it works and how to use it. Those who are familiar with me know that being short is not necessarily my strength, but I will try nevertheless. I would like to apologize to the authors in advance if something essential is lost in the shortening 😊 it was not intentional.
 

Donau PAC AQUACLEAR 

• acts as a fourth purification step
• supports sedimentation in the secondary clarifier
• precipitates phosphate
• can be dosed like a precipitant into the biological treatment step
• does not require any structural changes

Preface: Defining the scope of the AQUACLEAR field test

There are good reasons to implement the fourth treatment step and it will probably soon be mandatory for certain plants in the European Union. However, the established methods are not easy to implement at each sewage treatment plant.  Therefore, the straightforward application of Donau PAC AQUACLEAR could help.

It is known that powder activated carbon (PAC) and precipitants dosed separately do not negatively influence each other in their performance, on the contrary they even supplement each other.  The effect of dosing in the form of a combined product has not yet been investigated and should therefore be tested as part of the project:

1. It was tested whether the performance of the activated carbon in AQUACLEAR remains unchanged.
2. In the laboratory, AQUACLEAR was tested using effluents from different wastewater treatment plants.
3. The entire wastewater of a municipal sewage treatment plant was treated with AQUACLEAR.

• SAC₂₅₄: A simple photometric method; measures the absorbances in the UV range by substances that behave like micropollutants and can therefore be used as a rough indication for the treatment performance.
• Single substance analysis: Special equipment is used to determine the exact concentration of selected substances at trace levels.
• Bioassays: The effect of a mixture of substances on selected biological systems is determined. For example, a mixture of different micropollutants together could have an endocrine disrupting or carcinogenic effect. Such effects can be triggered by countless substances and combinations, making it impossible to assess them by single-substance analysis. Bioassays are used to estimate the potential of the wastewater (mixture of substances) regarding such specific effects.

Material, methods and analysis of the AQUACLEAR samples 

This part explains in detail which materials were used; how the tests were carried out and how the samples received were analyzed. This section describes the quality of the study and helps experts to repeat the experiments, but is less relevant for practitioners.

Results of the AQUACLEAR field test and discussion 

1. Comparison between activated carbon and AQUACLEAR in the laboratory
   An effluent sample from a wastewater treatment plant was treated with different amounts of activated carbon or AQUACLEAR. The single substance analysis and the bioassays show that more micropollutants and bioactive substances are removed by AQUACLEAR at the same amount of activated carbon used.


2. Treatment of different wastewater treatment plant effluents
   Micropollutants were removed from all three samples (6,000 p.e., 54,000 p.e., and 950,000 p.e.). An adjustment of the dosage to the wastewater characteristics is recommended. As a reference point, the DOC can be used.


3. Whole-stream treatment in a municipal wastewater treatment plant

• The dosage was chosen low enough that a residual of micropollutants could still be expected to be detectable.
• The SAC₂₅₄, an easy to measure indicator, showed a clear decrease during the application of AQUACLEAR. When the dosage was finished, it slowly increased again.
• In the second week of application of AQUACLEAR, the target for removal of micropollutants was already achieved. Following the end of the dosage, the removal rates slowly started to decrease, but were still significantly higher than before.
• The removal rates of common operational parameters, such as COD, P-total, N-total, were not affected notably.
• The addition of AQUACLEAR slightly increased the dry matter of the sludge. The sludge volume and the sludge volume index were slightly lower and the visible depth increased. There was not any activated carbon discharge observed.

If this (from my point of view) summary of the paper has raised your interest, I would like to recommend the full version of the publication to you. Its title is „Simultane Entfernung von organischen Spurenstoffen und Phosphor aus kommunalem Abwasser unter Einsatz einer Adsorptions-/ Fällmittelsuspension“ ("Simultaneous removal of organic micropollutants and phosphorus from municipal wastewater using an adsorbent/precipitant suspension") and it can be read in issue 3-4 of the ÖWAW 2023.