Adaptation and optimization of the AOP process for the drinking water supply of smaller supply units.

Duration:
2009-2010

Funding:
BLMFUW

Contact person:

Dr. Norbert Kreuzinger norbkreu@iwag.tuwien.ac.at

short description

Kurzinformationen zum Projekt

The contamination of groundwater with organic loads in the microgram range poses the problem, especially for smaller supply units, that otherwise high-quality raw water sources cannot be readily used for drinking water supply. With the AOP process (Advanced Oxidation with Ozone and Hydrogen Peroxide) there is a treatment process that can be used for a discontinuous "ON - OFF" operation according to demand. In this project the technical optimization of the AOP process for the removal of organic trace substances for small supply units (in the range of 20L/s) was carried out.
 
Motivation

Contamination of groundwater with organic loadings in the microgram range poses the problem, especially for smaller supply units, that otherwise high-quality raw water sources cannot be readily used for drinking water supply. This often concerns time-limited phases of peak coverage or longer phases of contamination that has occurred (e.g. temporary pesticide contamination). With the AOP process (Advanced Oxidation with Ozone and Hydrogen Peroxide) there is a treatment process, which is implemented in the Austrian Food Codex (Codex alimentarius austriacus) as a permissible treatment process and can also be used for a discontinuous "ON - OFF" operation according to demand. Based on the situation of the municipality Bad Fischau - Brunn, the technical optimization of the AOP process for the removal of organic trace substances, which in the present case are CHC loads in the Mitterndorfer Senke, for small supply units (in the range of 20L/s) was carried out.

In Austria, the use of AOP in drinking water supply is limited to the waterworks Moosbrunn in the Mitterndorfer Senke, which is operated by the City of Vienna (MA 31). However, the technical and operational implementation of this plant, with a throughput of 742 L/s, is oversized for typically affected communities and cannot be directly "downscaled". Neither design approaches, modes of operation, nor costs can be scaled up to a broader range of affected communities. Thus, the goal of this project is to establish procedural, operational, and economic bases for the technical implementation of the AOP process on a smaller scale.

Plant description

The AOP plant was manufactured by the company gwt- Gesellschaft für Wasser- und Wärmetechnik (2544 Leobersdorf) and is divided into two parts: All electrical equipment of the treatment plant (oxygen and ozone generator, residual ozone destroyer, plant control, measuring station with measuring probes, etc.) are located in a standard 20-foot container A standard 10-foot office container is attached to this plant container. Next to the containers are the concrete reaction tank and the storage tank.

Ozone is produced from oxygen, which is produced on site from air via an oxygen generator. The ozone is metered into the motive water line via an injector. Immediately after ozone dosing, H2O2 is dosed via a reciprocating pump. In the subsequent static mixer, the two oxidants are mixed into the main stream. The reaction of ozone and H2O2 with the water ingredients takes place in the reaction tank. Any outgassed residual ozone from the reaction tank and the receiver tank is sucked into the residual ozone destroyer where it is catalytically decomposed.

Operating settings

The CHC concentration of the raw water sample ranged between 8.6 and 12 µg/L during the test performance. To ensure compliance with the limit value of 10 µg/L, the following settings or concentrations of oxidants were determined:

Recommended dosing quantities for AOP drinking water treatment in Bad Fischau

On the one hand, these settings ensure reliable compliance with the CHC limit value and also enable compliance in the event of operational malfunctions due to failure of the ozone and/or hydrogen peroxide dosing, even if this means that there is no longer any certainty. The full drinking water analyses were carried out with these two settings and the relevant limit values of the TW Ordinance are complied with. Under the operating conditions described, there is also no relevant formation of undesirable oxidation by-products.

Economic efficiencyThe ozone concentration in the gas should be as high as possible Higher flow rates are economically more favorable than lower flow rates The investment costs are higher compared to the operating costs. Thus, the more drinking water is treated, the lower the specific costs The specific total costs are in the range of 5.6-9.2 €-cent/m³ when calculated according to LAWA (2005) If the depreciation period of the AOP plant is reduced to 10 years, the specific total costs increase to 10.2-17.1 €-cent/m³.