Within the context of EU-funded research project Powerstep the transferability of the innovative treatment concept CARISMO should be investigated on a full-scale wastewater treatment plant in a rural area. This concept contains an increased separation of primary sludge through wastewater filtration to use this in the digester for energy production. After filtration the flow to the SBR is reduced in COD load. As a consequence modifications of biocenosis and sludge structure are expected. Aim of this master thesis is to shift and evaluate the process during running operations. During commissioning only one out of two SBR was shifted. The fact allows a direct comparison to standard operations. Efficiency of filtration is shown by a balance of substance flow.

The aim of this master thesis was to investigate the transferability of the innovative treatment concept CARISMO on a full-scale wastewater treatment plant in a rural area. The idea of CARISMO is integrated in the EU-funded research project Powerstep and focuses on an increased separation of solid substances and their use for energy production with digestion. In the course of this work, principles and conditions for the change of occupancy were determined. Furthermore, preliminary tests were carried out to analyse the wastewater characteristics and the necessary resources for the projected flocculation and filtration stage. The technical feasibility and cost-effectiveness of the treatment concept has been shown with balances of material flows, energy and costs.

Energy and resource recovery from municipal wastewater is a pre-requisite for an efficient and sustainable water management in cities of the future. However, a sound evaluation of available processes and pathways is required to identify opportunities and short-comings of the different options and reveal synergies and potentials for optimisation. For evaluating environmental impacts in a holistic view, the tool of Life Cycle Assessment (LCA, ISO 14040/44) is suitable to characterize and quantify the direct and indirect effects of new processes and concepts. This paper gives an overview of new processes and concepts for upgrading existing wastewater treatment plants towards energy positive and resource efficient wastewater treatment, based upon an evaluation with LCA using data from pilot and full-scale assessments of the considered processes.

Due to intensive aeration in the activated sludge basins, a significant part of the organic matter in the wastewater often expressed as chemical oxygen demand (COD) is mineralized to the greenhouse gas CO2. Therefore the organic content in municipal wastewater is yet a widely untapped source of renewable energy. The Carismo project vision is to reduce the specific energy demand with a new treatment scheme based on a low energy microsieve separation process and at the same time, increase the specific energy recovery with an advanced separation of the organic fraction which is valorized in a digester. Therefore two treatment schemes were evaluated at lab scale and pilot scale with real wastewater. The raw wastewater contained a high COD concentration of 1000 mg/l. The first scheme treated the raw wastewater with a coagulation and flocculation step before a microsieve separation with a drum filter at 100 µm. The second scheme was similar to the first one with an additional MBBR (Moving Bed Biofilm Reactor) installed upstream the coagulation tank. The specific goal of the microsieve process was to increase the organic carbon extraction rate in scheme 1 to 60–80 %. The Pilot trial results showed an average COD extraction of 73–81 %. The average suspended solids (SS) removal was > 95 %. The soluble phosphorus removal was between 15 % and 70 % depending on the coagulant type and dose. With 20 mg Al/l, the effluent phosphorous concentration was around 2 mg/l. The MBBR upstream increased the COD transfer in the sludge by 3–8 %, but simultaneously the mineralization decreased the yield for the biogas process. This and the additional energy consumption of the aeration speaks against the separation process with an upstream MBBR.