About 25 hotels, restaurants and pubs in the rural community Heuvelland are situated in the area designated for individual water treatment. In order to meet the legislation by the end of 2015, each business needs to install an individual waste water treatment system (IWTS). To study this situation, three catering businesses were selected for further research. The aim of the study was to quantify the effluent quality and to assess IWTS performance for these catering businesses. First of all, the influence of discharging untreated waste water on the receiving surface water was examined. The results showed a decrease in water quality after the discharge point at every business. With the collected data, simulations with the software WEST were performed. With this software two types of IWTSs with different (buffer) volumes were modelled and tested for each catering business. The first type is a completely mixed activated sludge reactor and the second type is a submerged aerobic fixed-bed reactor. The results of these simulations demonstrate that purification with an IWTS is possible if the capacity is large enough and if an adequate buffer volume is installed and if regular maintenance is performed.

Titrimetry offers the possibility of simultaneous measurement at low cost of several (buffering) components. A first step in the study towards practical application of the titrimetric technique was the titrimetric analysis by up-or down-titration of standard solutions, standard mixtures, solids digester samples and water samples coming from autotrophic nitrogen-removal reactors. The resulting raw data were further processed with an Excel-based program. This program first converts the raw data into a buffer curve upon which a linear buffer capacity model is fitted to the experimental data by estimating the (buffer) concentrations and corresponding pKa values. As such the type of component and the concentration can be determined. As a second step the resulting calculated concentrations were analysed statistically to assess the accuracy and precision of the titrimetric technique. For this purpose, the data were paired, i.e. the difference between the concentration obtained with titrimetry and the concentration obtained with another technique such as colorimetry or gas chromatography was calculated. First the normality of the paired data was assessed. Then, a paired t-test (normal data) or a paired Wilcoxon test (normal data) was used to statistically compare the results obtained with the titrimetric technique to either the stock solution concentration or measurements with another method (colorimetry or gas chromatography). The statistical tests showed that, depending on the titrant concentration, concentrations from 50 mg/ℓ to 3 000 mg/ℓ could adequately be measured with the titrimetric technique.