Mobile TOC measuring station for process optimization
Development of a wastewater switch for the energy-efficient selective partial flow treatment of highly concentrated wastewater (ESTA) at municipal wastewater treatment plants
The research association ESTA is a merger of AKUT Umweltschutz Ingenieure Burkard und Partner, the Technical University of Berlin, FG Siedlungswasserwirtschaft and LAR Process Analysers AG. The aim was the development of an intelligent wastewater switch in the inflow of municipal sewage treatment plants for the separation of highly charged inflows and energy recovery by means of anaerobic treatment. The joint project “ESTA (FKZ 02WQ1382A-C)” was funded by the Federal Ministry of Education and Research (BMBF) within the framework of the SME-innovativ funding initiative.
As a result, peak inflow concentrations could be identified and evaluated with a time resolution of 6 minutes with regard to height and frequency in order to activate the wastewater diverter.
A successful operation of the wastewater switch and the anaerobic test reactor was possible despite the low peak concentrations and the low number of shock loads on the investigated wastewater treatment plant in combination with excess sludge. The simulation of the wastewater treatment plant showed that, despite the removal of the highly charged wastewater fraction and despite changes in the C:N ratio, the statutory monitoring values can be complied with under the underlying conditions (in particular the low ammonium inflow values). A maximum degree of electrical self-sufficiency of 75 % could be achieved.
A central component of the project was the construction and operation of a test plant at the Baruth (Brandenburg) sewage treatment plant, which was planned and installed in coordination with the project partners TU Berlin and AKUT. The project partner LAR was mainly responsible for the development of an adapted online analysis technology. Project start was 01.10.2016, project end was 31.03.2019.
With the help of the TOC-Online monitor a mechanism was controlled, which feeds inlet water of the sewage treatment plant to an anaerobic reactor from an adjustable threshold concentration. Both the analysed feed concentrations, the volume flows and loads fed into the reactor and the biogas produced in the reactor were evaluated.
Due to the implementation of the TOC online monitor on a trailer, the measuring equipment is now also available for mobile use. Measurement campaigns at other sewage treatment plants and at two industrial sites prove the operational capability. The basic load could be clearly determined and the concentration peaks could be evaluated with regard to height and frequency. It was possible to define threshold values in concentration and volume of an impact load which makes the investigation of a general conversion of the process with separate anaerobic sludge treatment useful.
“Although the Baruth wastewater treatment plant under investigation with the evaluated impact loads is below the threshold values determined and a further investigation does not appear to be appropriate here, the results of the other sites investigated certainly show potential”, explains project coordinator Dipl. Ing. Thilo Burkard (AKUT).
The participating project partners are accordingly optimistic that the new concept can be applied to new construction and conversion of wastewater treatment plants. A measurement campaign with the mobile measuring device is therefore planned for other wastewater treatment plants.
Further information: Thilo Burkard
Retention soil filters for urban waters in China
Thousands of canals run through the cities in China. In the shallow estuaries of the major rivers, they have traditionally served as traffic routes navigable by barges. With rapid and extremely dense development, the drainage of water became increasingly important. However, this was accompanied by ever-increasing pollution. Hydraulically overloaded sewers and high material loads in rainwater runoff today lead to excessive pollution of surface waters. This has a bad effect on their oxygen balance, which leads to serious odour nuisance, especially in the warm season.
Since the government declared the remediation of these waters to be a central task for all municipalities, many technologies have been tested. In most cases, however, success has not been achieved. Obviously, the problem could not be solved by internal measures in the waters alone. In two cases, retention soil filters were now used, which are suitable for the short-term absorption of high hydraulic loads from the combined sewer and stormwater system and thus for treatment before overflowing into the sewer.
Within the framework of the BMBF-funded KEYS joint project entitled “Pioneering technologies for the sustainable management of urban watersheds as a key factor for the successful implementation of the “sponge city” concept”, the effect of these systems is to be demonstrated and investigated in parallel. Retention soil filters were developed in Germany and represent the key technology in this country for both centralised and decentralised treatment of rainwater and combined sewer overflows.
The engineers of AKUT, who have been working in China as consultants for 10 years, are aware that German technology cannot always be transferred one to one abroad. In particular, the data basis for optimal dimensioning is often missing there. In cooperation with the project partners, the prerequisites are now being created. During our visit in December 2019, the sampling locations for the planned measurement campaigns in 2020 were examined and operational data were obtained. The installation of online probes and rain recorders was prepared.
The two demonstration sites, each with 3 000 m² retention filter area, are located in Suzhou, Jiangsu Province. While the first retention soil filter at the Zhujing Channel has been in operation since 2018, the second filter at the Hongshuanglou Channel was not completed until winter 2019.
In contrast to the more water-rich regions, these soil filters will also be used in arid climates such as Beijing. A multifunctional use of the soil filters is being tested for this purpose. This means that in dry weather, the available filter area will be used for direct treatment of surface water. This protects the plant filters from drying out and simultaneously leads to an increased cleaning effect.
The joint project is led by the Institute for Sanitary Engineering of the Leibniz University of Hannover (ISAH) and funded by the Federal Ministry of Education and Research for 3 years within the framework of the funding measure “CLIENT II – International Partnerships for Sustainable Innovations”.
Photo: Till Ermisch (AKUT) interviews Ying ZHANG from Suzhou DeHua Eco Technology Ltd. about the discharge points at the restored Hongshuanglou Channel.
Presentation: IE expo China 2021
Design recommendation for combining nature based and technical solutions
In the European joint project AquaNES, various combinations of nature based and technical systems were investigated for their suitability for wastewater treatment from 2016 to 2019. The results were described in a handout for planners and operators describing such and comparable systems. The recommendations show the potentials and reasonable applications of such combinations.
The first part of the document deals with soil filters as part of combined systems and describes possible combinations with technical pre- and post-treatment. The different possible applications of constructed wetlands as primary, secondary or tertiary treatment as well as dual use for combined sewer overflows and as a tertiary treatment stage are highlighted. Important design parameters, in particular the German code of practice DWA A-262 (2017) for the dimensioning, construction and operation of constructed wetlands for municipal wastewater treatment are summarized here and combined with the results from the demonstration sites and the experience of the authors.
In the second part, the five AquaNES sites in Greece, Germany, and Great Britain, their different applications, design and operation data, and monitoring results are presented. The two Greek sites, the Antiparos and Thirasia WWTPs, are both located on tourist-oriented islands in the Aegean Sea. The solution at Antiparos focused on creating a robust, nature-based system that could handle fluctuating hydraulic and organic loads and meet the Greek standard of water reuse for irrigation. At Thirasia, a soil filter was integrated into a number of different engineering processes. Here, photocatalysis via TiO2 was also experimented with and downstream membrane filtration was tested. In Germany, an innovative retention soil filter was constructed in Rheinbach (Erftverband) for the combined use as a fourth treatment stage and for treating combined sewer overflows. At the Schönerlinde wastewater treatment plant, the combination consisted of an ozone plant and a downstream soil filter. Here, the retention of organic micropollutants such as pharmaceutical residues and metabolites in the effluent of the wastewater treatment plant was also demonstrated. Finally, the effectiveness of soil filters with reactive filter material made from blast furnace slag was investigated in long-term operation at the Packington site (UK).
Further information: Heribert Rustige