Different technologies for tertiary wastewater treatment are compared in their environmental impacts with life cycle assessment (LCA). Targeting very low phosphorus concentration (50–120 µg/L) and seasonal disinfection of wastewater treatment plant (WWTP) secondary effluent, this LCA compares high-rate sedimentation, microsieve, dual media filtration (all with UV disinfection), and polymer ultrafiltration or ceramic microfiltration membranes for upgrading the large WWTP Berlin-Ruhleben. Results of the LCA show that mean effluent quality of membranes is highest, but at the cost of high electricity and chemical demand and associated emissions of greenhouse gases or other air pollutants. In contrast, gravity-driven treatment processes require less electricity and chemicals, but can reach significant removal of phosphorus. In fact, dual media filter or microsieve cause substantially lower specific CO2 emissions per kg P removed from the secondary effluent (180 kg CO2-eq/kg P, including UV) than the membrane schemes (275 kg CO2-eq/kg P).

For improved exploitation of the energy content present in the organic matter of raw sewage, an innovative concept for treatment of municipal wastewater is tested in pilot trials and assessed in energy balance and operational costs. The concept is based on a maximum extraction of organic matter into the sludge via coagulation, flocculation and microsieving (100 µm mesh size) to increase the energy recovery in anaerobic sludge digestion and decrease aeration demand for carbon mineralisation. Pilot trials with real wastewater yield an extraction of 70–80% of total chemical oxygen demand into the sludge while dosing 15–20 mg/L Al and 5–7 mg/L polymer with stable operation of the microsieve and effluent limits below 2–3 mg/L total phosphorus. Anaerobic digestion of the microsieve sludge results in high biogas yields of 600 NL/kg organic dry matter input (oDMin) compared to 430 NL/kg oDMin for mixed sludge from a conventional activated sludge process. The overall energy balance for a 100,000 population equivalent (PE) treatment plant (including biofilter for post-treatment with full nitrification and denitrification with external carbon source) shows that the new concept is an energy-positive treatment process with comparable effluent quality than conventional processes, even when including energy demand for chemicals production. Estimated operating costs for electricity and chemicals are in the same range for conventional activated sludge processes and the new concept.

This paper describes an innovative concept for treatment of municipal wastewater, targeting the improved exploitation of the energy content present in the organic matter of raw sewage. The concept is based on a maximum extraction of organic matter into the sludge via coagulation and micro-sieving (100 µm mesh size) to increase the energy recovery in anaerobic sludge digestion and decrease aeration demand for carbon mineralisation. Pilot trials with real wastewater yield a COD extraction of 70-80% of total COD into the sludge while dosing 15-20 mg/L Al and 5-7 mg/L polymer with stable operation of the microsieve and effluent limits below 2-3 mg/L total phosphorus. Anaerobic digestion of the sludge results in high biogas yields of 600 NL/kg organic dry matter input (oDMin) compared to 430 NL/kg oDMin for mixed sludge from a conventional activated sludge process. The overall energy balance of the new concept for a 100 000 pe treatment plant (including biofilter for post-treatment with full nitrification and denitrification with external carbon source) shows that the new concept is an energy-positive treatment process with comparable effluent quality than conventional processes, even when including energy demand for chemicals production. Estimated operating costs for electricity and chemicals are in the same range for conventional activated sludge processes and the new concept

Das Projekt soll mögliche Entlastungseffekte für die Berliner Gewässer durch Einsatz geeigneter Maßnahmen zur Reinigung von Straßenabläufen aufzeigen.

The presented work studies the influence of the sampling strategy on the quality of locally calibrated UV-VIS probe measurements in combined sewer overflows (CSO) and the receiving river. Results indicate that UV-VIS spectrometers are not able to provide reliable measurements of water quality in urban stormwater without being calibrated to local conditions with laboratory analyses of water samples. The use of the global calibration (supplied by the manufacturer) led to errors of at least 30% and 45% for CSO load and river concentration of chemical oxygen demand (COD), respectively. Even with reliable local calibration, COD loads contained significant uncertainties close to 20%. Uncertainties in COD load and concentration decrease below 30% if more than 15-20 samples (i.e. 3-4 stormwater events) are sampled for local calibration. The effort and associated sampling costs to gain more than 15-20 samples are much less effective, since load and concentration uncertainties remain relatively stable with an increasing number of samples used for the calibration. The presented analysis aims at supporting practitioners in the planning, operation and calibration of UV-VIS spectrometer probes.

The present study aims to explore the relationship between rainfall variables and water quality/quantity characteristics of combined sewer overflows (CSO), by the use of multivariate statistical methods and online measurements at a principal CSO outlet in Berlin (Germany). Canonical correlation results showed that the maximum and average rainfall intensities are the most influential variables to describe CSO water quantity and pollutant loads whereas the duration of the rainfall event and the rain depth seem to be the most influential variables to describe CSO pollutant concentrations. The analysis of Partial Least Squares (PLS) regression models confirms the findings of the canonical correlation and highlights three main influences of rainfall on CSO characteristics: (i) CSO water quantity characteristics are mainly influenced by the maximal rainfall intensities, (ii) CSO pollutants concentrations were found to be mostly associated with duration of the rainfall and (iii) pollutants loads seemed to be principally influenced by dry weather duration before the rainfall event. The prediction quality of PLS models is rather low (R² < 0.6) but results can be useful to explore qualitatively the influence of rainfall on CSO characteristics.