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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