The limits of sensors in harsh environments are discussed. Failures of sensor materials, interconnects, and cables are shown. Remote measurements can be solutions to overcome material problems. Sensor material and measurement systems are presented for cases such as high temperature, high pressure, toxicity, explosiveness, nuclear radiation, and high electromagnetic pulse (EMP) levels.

Denitrification with biogas consisting of approximately 60% methane was tested over one year in three types of lab-scale reactors. Denitrification of sanitary landfill leachate with biogas as a sole carbon source was found to be possible. Denitrification rates from 60 mg NO3–N/l. d with an activated sludge reactor, 150 mg NO3–N/l. d with a trickling filter and 550 mg NO3–N/l.d with a fluidized bed reactor were obtained. The oxygen concentration played a significant role in process optimization. Not only high concentrations of oxygen in the liquid medium but also low oxygen concentrations in the aeration gas inhibited denitrification.

The theoretical assumptions to understand the elution mechanism of the discontinuous solution fractionation and complete elution method could be confirmed for the system poly(viny1 acetate)/butyl acetate/cyclohexane. In this case the process of complete elution, however, can only be carried out with an unfavorable high consumption of time and material. The complete elution method with all its advantages can be preserved, if the process is carried out as multistage process with a limited number of discontinuous steps. By means of such a multistage procedure improved separation results were achieved compared with the conventional single stage procedure. Furthermore some results are given which show a decrease of the separation effect of solution fractionation due to procedural limitations.

At Wolfsburg for a load of 100,000 p.e., the step-feed activated sludge process for nitrogen removal is successfully in operation. Due to the high denitrification potential (BOD:TKN = 5:1) the effluent total nitrogen content can be kept below 10 mg l−1 N; furthermore by some enhanced biological phosphate removal about 80% phosphorus may be removed without any chemicals.

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