Unformatted text preview: ffer from one WWTP to another, and this may be, the expected one. as expected, a result of design, operation or both. It was • The UASB reactors showed good BOD and COD removal also observed that none of the WWTPs that presented efﬁciencies and a poor performance regarding TSS, FC removal efﬁciencies above the upper limit reported by and nutrients, in terms of the reference ranges reported the literature were operating within the usual design and in the literature. The performance achieved by the operation parameters. Table 10 | UASB reactors followed by post treatment (UASB þ Operating conditions of the WWTPs with signiﬁcantly different performances
Mean performance above the usual Mean performance below the usual % overloaded % overloaded Technologies Parameter % underloaded % underloaded FP Ls
0 AP þ FP Ls
50 AS F/M ratio
0 UASB Upﬂow velocity
0 55 S. C. Oliveira & M. von Sperling | Performance of wastewater treatment technologies POST) was the closest one with the expected values from Journal of Water, Sanitation and Hygiene for Development | 01.1 | 2011 ACKNOWLEDGEMENTS the literature.
The authors would like to thank FINEP, FAPEMIG, CNPq,
SABESP, COPASA, FEAM, USP and municipalities for Inﬂuence of the operational conditions • their support and cooperation during the course of the In general, the inﬂuence of the loading conditions research. was very small and scattered in all the treatment
processes. • A single variable or a group of variables could not be used
to explain the differentiated performances among all the
WWTPs. The contribution and inﬂuence of each variable
seemed to differ from one WWTP to another and, as
expected, this is likely to be a combination of multiple
design and operational aspects. Final remarks
The purpose of the paper was to present a diagnosis of the
wastewater treatment reality in a developing country, reﬂecting actual operating conditions. If this portrays the existing
reality, care should be taken in not considering that the
expected performance of the treatment technologies will
always be within the range obtained. From the literature
and from results from some of the plants investigated, the
expected performance may be higher than the overall performance achieved. This shows that improvements in the
current situation are possible, thus serving as an incentive
to designers and plant operators.
In view of the results, it is evident that each WWTP
should be evaluated individually to justify either good or
poor performances, since they result from several factors.
The designer and operator are required to have a broad
and integrated knowledge of each system, involving not
only the implications of the applied hydraulic and organic
loads, but also factors not always directly measurable.
Speciﬁc characteristics of each inﬂuent, microbiolog...
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