Ated in terms of the inuence of design and operation

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Unformatted text preview: ng to time (HRT), influent flow and monitoring index (MI). the statistical tests. Similarly to the activated sludge, the statistical tests did The WWTPs considered unusual, that is, whose per- not show any influence of the organic and hydraulic load- formance was either significantly lower or higher than the ing, as well as flow and monitoring index, on the effluent mean performance achieved by the technology, were evalu- quality. ated in terms of the influence of design and operation factors 53 S. C. Oliveira & M. von Sperling Figure 10 | | Performance of wastewater treatment technologies Journal of Water, Sanitation and Hygiene for Development | 01.1 | 2011 Relationship among HRT, v, flow, monitoring index and effluent BOD concentration, BOD removal efficiency – UASB reactor. Note: The symbol ⊗ represents one WWTP that had influent flow equal to 18,000 m3 dÀ1 (outside the axis scale). 54 S. C. Oliveira & M. von Sperling Table 9 | | Performance of wastewater treatment technologies WWTPs with significantly different performances, according to statistical tests (significance level α ≤ 5%) FP AP þ FP Number of WWTPs evaluated 73 38 12 9 % significantly above the mean performance 0 7 23 10 % significantly below the mean performance 1 5 46 Journal of Water, Sanitation and Hygiene for Development UASB 01.1 | 2011 CONCLUSIONS AND FINAL REMARKS Performance evaluation 10 AS | • A great variability was noticed in the effluent concentrations and in the removal efficiencies, considering all analysed constituents and all treatment technologies. • The septic tank þ anaerobic filter (ST þ AF) process presented a performance below that reported in the on their performance. These WWTPs were analysed in order to verify the possible existence of a better performance when literature. • than expected, considering COD, TSS and TN removal the systems operated within the range recommended for efficiencies. However, good TP and FC removal efficien- design and operation. Table 10 presents the operating conditions of the WWTPs that were significantly different, either positively The performance of the facultative ponds (FP) was lower cies were achieved. • The anaerobic ponds þ facultative ponds (AP þ FP) showed a good performance in terms of BOD, COD, TP or negatively, within each treatment technology. It was and FC removal, with a significant percentage of not possible to establish a consistent relationship between the removal efficiency and the operational variables. WWTPs with efficiencies within and even above the Removal efficiencies either above or below the mean values reported by the literature. value of the technology were observed in WWTPs operat- • The performance presented by the activated sludge (AS) ing either overloaded or underloaded, indiscriminately. plants, considering organic matter removal, was the high- The contribution and influence of each variable seemed est among the evaluated systems, although it was below to di...
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