The aim of the study was to investigate the influence of moderate temperatures on the efficiency of a full-scale anaerobic treatment system consisting of a primary sedimentation unit (PST) and an anaerobic baffled reactor (ABR, approx. 10 m 3 ). Therefore, two trials with different test setups in series were carried out (1st trial: continuous load; 2nd trial: diurnal variation load). The plant was fed with municipal wastewater and operated at temperatures between 8 and 24°C. The mean efficiency of the ABR was low, compared to the one of the PST. At 10°C, only 10% of the COD was removed. The COD (chemical oxygen demand) removal efficiency of the plant (PST + ABR) averaged 50%. At low temperatures, volatile fatty acids began to accumulate. In both trials, the contents of total suspended solids in the sludge bed differed distinctly and influenced the effort for desludging. • Practitioner points• The operation of ABR in combined collection systems depends on the efficiency of the pretreatment unit. • At cold temperatures, an ABR has no advantages compared to conventional pretreatment processes. • For use under moderate conditions, the design must be adjusted.

Tools for hot wire rolling are exposed to high thermal, mechanical and tribological loadings during service. Ceramic materials such as silicon nitride possess good mechanical and tribological properties up to temperatures where most of today' roller materials do not exhibit acceptable reliability. In the present paper basic mechanical properties under thermal and mechanical loading as well as the damage behaviour of Si3N4 have been investigated in high cycle thermal fatigue and dynamic as well as cyclic four point bending tests. In fretting fatigue tests the behaviour of Si3N4 under near-service conditions, as they appear during application in the hot wire rolling process, has been analysed. It is shown that in the temperature range investigated pure thermally induced loading leads to the same damage mechanism as pure mechanical loading and therefore thermally induced stresses can be directly added to any mechanical loading. The isothermal four point bending tests confirm the existence of a cyclic fatigue effect. With the fretting fatigue experiments the limits of high-performance ceramics such as Si3N4 are shown. Under the complex loading, surface flaws are produced leading to a severe lifetime reduction compared to plain mechanical and thermal loading.

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This paper includes a comprehensive literature review of sludge composition data from wastewater treatment plants. 722 data sets from 249 sources were used to establish typical ratios between COD and solids-based parameters and to verify rule-of-thumb values, respectively. Confirmation of these typical ratios can also be accomplished by using biochemical composition data. It is shown that a correlation between data from proteins, lipids and carbohydrates analysis can be related to COD/VSS ratios. Finally, using the findings from the literature review, the organic and inorganic conversion factors of COD fractions in activated sludge models are adjusted to solids-based parameters. It was shown that with the adjustments of the factors and a partition of the particulate inert fraction into a fraction assigned to the influent and a fraction assigned to the endogenous products, a better agreement with the ratios of COD/VSS in the individual sludge streams can be established.

For successfully operating a vertical flow constructed wetland, the uniform distribution of wastewater on the surface of the soil filter is essential. In research, however, this aspect is often overlooked. This study presents a methodology for assessing discharge uniformity from perforated pipe systems via hydraulic modeling. First, the requirements and conditions for the simulation of perforated pipe systems are investigated and the model basics are explained. Then the whole process of model build-up, calibration, application and analysis is presented and discussed. The modeling is done by the software EPANET and supported by pressure measurements in the pipe system of a small wetland treating domestic sewage. A crucial factor in the modeling process is the choice of loss coefficients in dividing junctions. Different approaches for calculating such coefficients are compared. Model calibration is undertaken via the multicriterion optimization algorithm NSGA-II. By calibrating two parameters, a reasonable goodness of fit with the measured pressure values was achieved. Model results show that distribution uniformity of the pipe system in question is poor. An outlook on potential applications of hydraulic modeling of perforated pipe systems in vertical flow constructed wetlands is given.