A continuous mashing system controlled by mean residence time

Continuous processes offer more environmentally friendlier beer production compared to the batch production. However, the continuous production of mashing has not become state-of-the-art in the brewing industry. The controllability and flexibility of this process still has hurdles for practical implementation, but which are necessary to react to changing raw materials. Once overcome, a continuous mashing can be efficiently adapted to the raw materials. Both mean residence time and temperature were investigated as key parameters to influence the extract and fermentable sugar content of the wort. The continuous mashing process was implemented as continuous stirred tank reactor (CSTR) cascade consisting of mashing in (20°C), protein rest (50°C), β-amylase rest (62-64°C), saccharification rest (72°C) and mashing out (78°C). Two different temperature settings for the β-amylase rest were investigated with particular emphasis on fermentable sugars. Analysis of Variance (ANOVA) and a post-hoc analysis showed that the mean residence time and temperature settings were suitable control parameters for the fermentable sugars. In the experimental conditions, the most pronounced effect was with the β-amylase rest. These results broaden the understanding of heterogenous CSTR mashing systems about assembly and selection of process parameters

Enhanced estrogen removal in activated sludge processes through the optimization of the hydraulic flow pattern

The removal of β-estradiol (E2) and α-ethinylestradiol (EE2) in biological wastewater treatment plants (WWTP) would need to be improved in order to comply with prospective Environmental Quality Standards (EQS) of 0.4 and 0.035 ng.L^-1 respectively. The effluent concentration of a micropollutant in an activated sludge process is a function of the removal rate, the hydraulic retention time (HRT) and the flow pattern, which is usually overlooked. In order to better understand this aspect, we carried out tracer studies in eight WWTPs in the UK and found that relatively modest changes in aeration tanks would translate into tangible improvements in their flow pattern. We further evaluated the degradation rates for E1 (estrone), E2, E3 (estriol) and EE2 in each WWTP and we estimated that the modification of the flow pattern would be sufficient to place effluent concentrations of E2 (23.2 L∙g_VSS^-1∙d^-1<k_bio<210 L∙g_VSS^-1∙d^-1) far below the prospective EQS, while EE2 (0.3 L∙g_VSS^-1∙d^-1<k_bio<2.9 L∙g_VSS^-1∙d^-1) would have to rely on river dilution for compliance. Regarding E1 and E3, with no prospective legislation, the modifications would place E3 (9.9 L∙g_VSS^-1∙d^-1<k_bio<39.5 L∙g_VSS^-1∙d^-1) effluent concentrations easily below its predicted no-effect concentrations (PNEC = 60 ng.L^-1) while for E1, (2.6 L∙g_VSS^-1∙d^-1<k_bio<19.2 L∙g_VSS^-1∙d^-1) it would very much depend on the degradation rates of the specific WWTP (PNEC = 6 ng.L^-1). Improvement in flow pattern had the additional benefit of improving the effectiveness of other plausible changes in HRT or biological removal rates. Managing the flow pattern of existing WWTPs is a cost-efficient tool for managing the fate of estrogens.

A quantitative analysis of swimming pool recirculation system efficiency

The primary objective of this study was to conduct a quantitative analysis of the hydraulic efficiency of a 1:25 bench-scale swimming pool and to determine whether the recirculation efficiency could be increased by modifying parameters such as turnover rate, inlet/out configuration, and extent of mixing within the pool. Salt tracer studies were conducted using KCl to determine the residence time distribution and describe the hydraulic characteristics of the pool. The results indicated that the removal of the tracer always followed an exponential decay curve, i.e. 63, 86, 95% for the first, second, and third turnover periods, respectively. In the majority of experiments, the exponential decay rate matched the inverse of the theoretical hydraulic detention time of the system. The results showed that none of the investigated parameters had any significant impact on the tracer removal efficiency. Increasing removal efficiencies of current treatment technologies such as sand and cartridge filters from approximately 25-90% would provide significant improvements in the rate of removal of Cryptosporidium-sized particles. Improving the treatment efficiency beyond 90% would have little additional impact, but further improvements could be achieved by decreasing the system turnover rate.