Recent infrastructure studies underline the general deterioration of sewer systems and the risk reversing public health, environment and increasing costs (ASCE, 2009). Aging pipes have not been inspected, replaced or rehabilitated rapidly enough to prevent sewer deterioration and increasing system failures (Tuccillo et al., 2010). According to a need survey conducted by EPA (2008), total funding needs for replacement, rehabilitation and expansion of existing collection systems for a 20 year period in the USA is 82.7 billions $, i.e. 28% of the total need of public agencies for wastewater treatment and collection. In the last 30 years, most municipalities have invested in sewer system expansion and treatment plant upgrade but a relatively small component has been allocated to the improvement of sewer system condition.

Managed Aquifer Recharge (MAR) is a means to replenish aquifers in case of over-abstraction and store water, especially in regions with semi-arid or arid climate. For water re-use schemes MAR can offer additional treatment in the subsurface so the CO2-footprint can be reduced. Pre-treatment via ozonation and dual media filtration before infiltration of treated wastewater was studied to compare the obtained water quality to guidelines for water reuse. While the removal of bulk parameters such suspended solids or chemical oxygen demand were easily reduced by ozonation and filtration, the disinfection turned out to be the limiting process.

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a posttreatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.

Risk-based management approaches are more and more used in the water sector and are promoted by the WHO. As a first step towards an overall risk-based management approach of the agricultural wastewater reuse concept of Braunschweig a quantitative microbial risk assessment (QMRA) is conducted. A 1000 trial Monte Carlo Simulation is used for the assessment of microbial risks for fieldworkers and nearby residents. As a tolerable value of risk an additional disease burden of 1 µDALY is set following the current WHO guidelines. Concerning microbial risks risk-based targets are set in terms of additional required pathogen reduction in the STP Steinhof. Based on the model results an additional reduction of 1.5log units is derived for viruses, for which the highest annual risks of infection per person per year (pppy) is calculated in all scenarios.

Das vorgestellte modellbasierte Werkzeug bildet Mischwasserüberläufe aus dem Berliner Mischkanalsystem und deren kurzfristige Auswirkungen im Gewässer ab. Es soll für die Massnahmenplanung und die Berechnung von Zukunftsszenarien verwendet werden. Das Werkzeug zeigt eine gute Übereinstimmung mit Messungen bezüglich des Verlaufes der Sauerstoffkonzentration im Gewässer und des Auftretens kritischer Bedingungen für die Fischfauna.