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The wastewater treatment process is based on complex chemical, physical and biological mechanisms that are closely interconnected. The efficiency of the system (which depends on compliance with national regulations on wastewater quality) can be achieved through the use of tools such as monitoring, that is the detection of parameters that allow the continuous interpretation of the current situation, and experimental tests, which allow the measurement of real performance (of a sector, a single treatment or equipment) and comparison with the following ones. Experimental tests have a particular relevance in the case of municipal wastewater treatment plants fed with a strong industrial component and especially in the case of plants authorized to treat aqueous waste. In this paper a case study is presented where the application of management tools such as careful monitoring and experimental tests led to the technical and economic optimization of the plant: the main results obtained were the reduction of sludge production (from 4,000 t/year w.w. (wet weight) to about 2,200 t/year w.w.) and operating costs (e.g. from 600,000 €/year down to about 350,000 €/year for reagents), the increase of resource recovery and the improvement of the overall process performance. [ABSTRACT FROM AUTHOR]

In the present work, the thermophilic aerobic membrane reactor technology was studied for the treatment of high strength aqueous wastes mainly containing dyes, surfactants and solvents. The thermophilic biomass resilience and the process stability under critical conditions (such as rapid rise of the mixed liquor pH, oxygen supply interruption, etc.) were also evaluated. The experimental work was carried out with the use of a pilot plant at semi-industrial scale, which was managed throughout for 14 months; the operation temperature was 49 °C and the organic loading rate was increased from 3 to 12 kgCOD m−3 d−1. Critical conditions, especially the interruption of oxygen supply, affected the pilot plant performance but did not cause a complete system break down. After the temporary reduction of process performance, also proven by the decrease in the oxygen consumption, the normal working conditions were restored. Moreover, the longer non-aerated phase involved a significant reduction (40%) of volatile suspended solids concentration in the biological reactor and the increase of 30% in foaming power; nevertheless, once the oxygen supply was reactivated, optimal conditions were rapidly restored. Therefore, the study showed the high resilience of the thermophilic biomass, which was able to recover full functionality after critical events. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including phases of municipal wastewater treatment, model of developing integrated water demand model, and effect of anaerobic reject water on operational characteristics of wastewater treatment.