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Biofilm-Hybrid-Processes for Wastewater Treatment in North African Climate: Conventional Carrier vs Recycling Material for Capacity Increase

Groundplan of the WWTP-block showing the three different process variations that are compared

Keywords: Upgrading WWTP, Biofilm-carrier, Hybrid activated sludge, Capacity increase 

In the growing city of El Gouna about 23.000 inhabitants and tourists are currently connected to a central activated sludge wastewater treatment plant. As the growing city reaches the WWTP-site new constructions are not allowed even though the inflow increases. The Carsten Riechelmann is currently supporting the city services through a real scale test of different options to increase the WWTP’s capacity. A comparison is running between an optimization of the conventional activated sludge process and the application of a fixed and a moving bed biofilm carrier hybrid process. In the lab a pilot scale comparison is running between the common carrier products and potential alternatives from PET-Bottle-Recycling.

The central WWTP treats in total up to 3,000 m³/d of mainly domestic waste water to be reused in the city owned irrigation water network. Due to the utilization for plant irrigation the treatment does not include nutrient removal and just needs to ensure carbon removal and nitrification. The part of the WWTP that is used for the comparison is fed by only one inflow construction but is subdivided in three separated streams with own aeration tank, settler and return sludge flow each.

After the installation of Thomson weirs for the measurement of the flow distribution to each stream and a complete refit of the aeration grit the set-up is ideal for a comparison of three different process options treating the same wastewater inflow while operating in 100% identical geometry:

A. Activated sludge system as a reference for the original process

B. Integrated fixed bed activated sludge system (Jäger Envirotech Biocurlz Textile: 940 holding bars with 6 laces each being 2.7 m long = 15222 m which corresponds to about 18,000m² Biofilm-surface)

C. Hybrid moving bed activated sludge system (Chinese copy of Kaldnes K1 Carrier: 10% filling of 360m³-reactor = 36m³ with an effective surface of 500m²/m³ = 18,000 m² Biofilm-surface)

As occasionally measured data sets of process parameters are insufficient to accurately observe differences between the streams an online measurement system was installed. Currently an S::can system is measuring COD, TSS, NO3, NH4, pH, O2, Temperature in the inflow and the three different effluent streams. Using this setup of continuous registration day-curves are generated to see the different dynamical behavior of the different streams.

Another option to compare the kinetic behavior of the different biomass combinations is the measurement of the oxygen uptake of a certain amount of biomass after the dosage of a defined amount of wastewater. With this approach it is possible to measure the exogenous respiration rate for the degradation of the injected wastewater sample. It allows for a monitoring of the microbial activity if exposed to a certain type of substrate. Thus it is possible to characterize the different biomass biocenosis that are developing in the different process configurations. Furthermore it is possible to test which fraction of the degradation activity comes from the suspended biomass alone and which one from the attached biomass in the biofilm.

Parallel to the tests in the central WWTP in the laboratory of the Campus El Gouna a pilot scale test-plant is running with bottle caps as potentially cost efficient biofilm carrier option. Bottle caps from the local El Gouna recycling factory are having ~180 m²/m³ so only about 1/3 of the K1-carrier surface. But they are available in Egypt for 30 – 40 €/m³ compared to 250 - 300 €/m³ for the Chinese copy of Kaldnes K1.

In the scope of this project the first detailed examination of different biofilm carrier applications in the warm Egyptian climate takes place. The approach examined mostly under the European conditions of <15° still lacks verification of the effectiveness at temperatures >25°C. Thus the coming summer is necessary to complete the project data acquisition. As Egypt faces more and more overload problems in many of its WWTP the results of this real scale research will help decision makers all over the country to evaluate capacity increase options regarding their performance but also regarding their cost effectiveness.

Ecoglobe project at Campus El Gouna: “Waterbase” test plant

Waterbase system

Funded by the Climate KIC Program the following project is a collaboration of TU Berlin Campus El Gouna and Ecoglobe GmbH. It comprises the construction of the decentralized wastewater system “Waterbase”. Furthermore checking the functioning of the whole plant and examining the efficiency by changing the dimensions of the filter and varying the wastewater load.

From technical point of view, Waterbase is a constructed wet land without the vegetation build underground. In future it shall be placed close to where wastewater is generated. By this wastewater reuse projects are easier to implement and expensive sewer systems can be avoided. In the test-plant at the Campus El Gouna the reliability and the quality of the treatment results will analyzed to find out if it can be used as a safe source of reclaimed water e.g. for irrigation in landscaping.

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