An apparatus was constructed for testing the influence of paddle shape and depth and paddle wheel speed and diameter on oxygen-transfer characteristics of paddle wheel aerators. Paddles triangular in crosssection were more efficient than other paddle shapes. Standard oxygen transfer rate (SOTR) increased with increasing paddle depth and paddle wheel speed while standard aeration efficiency (SAE) declined. For a particular depth and speed, SOTR increased with increasing paddle wheel diameter. The greatest SAE (2·96 kg O2 kWh−1) was achieved with a 91 cm diameter paddle wheel with triangular paddles operated at 77 rev min−1 and 12·5 cm paddle depth. Three companies made floating, 7·5 kW electric paddle wheel aerators according to design specifications developed in this research. These commercial aerators had high values for SOTR (18·8–21·8 kg O2 h−1) and SAE (2·7–2·9 kg O2 kWh−1) and were much more efficient than other aerators used in channel catfish farming.
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"A wide variation in performance of aerators in terms of standard aeration efficiency was found, like, Taiwanese aerator (1.17 kg 0 2 /kWh), Japanese aerator (1.03 kg 0 2 /kWh) and Auburn university design (2.25 kg 0 2 /kWh) (Busch et al. 1974; Boyd and Watten 1989; Boyd, 1998; Colt, 2000a; 2000b). Ahmad and Boyd (1988) provided optimum designs of paddle wheels and Moulick et al. (2002) used similarity criteria in predicting the oxygen transfer performance of paddle wheel aerators. The centrifugal surface aerator along with the paddle wheel surface aerator had been traditionally used in wastewater treatment (Stukenberg et al., 1977; ASCE, 1997). "
[Show abstract][Hide abstract] ABSTRACT: Oxidation ditch process is used to treat the municipal and domestic sewage. The untreated sewage generates fouling smell, harmful bacteria, etc. which is hazardous for public health and degrades the environment by librating noxious gases. This paper examines the use of curved blade aerator for oxidation ditch process. The rotor, which controls the aeration, is the main component of the aeration process. Therefore, the objective of this study is to find out the variations in overall oxygen transfer coefficient and aeration efficiency for different configurations of aerators by varying the parameters like speed of aerator, depth of immersion and blade tip angles so as to yield higher values of overall oxygen transfer coefficient and aeration efficiency. Four aerators of different configuration were developed and fabricated in the laboratory and were tested for above mentioned parameters. A mathematical model is developed for predicting the values of kLa and aeration efficiency which has R2 values of 0.97 and 0.99 for experimentally determined and calculated values. In laboratory studies, the optimum value of overall oxygen transfer coefficient and aeration efficiency were observed to be 10.33/h and 2.269 kg O2/kWh for aerator speed of 48 rpm, 5.5 cm depth of immersion and 47o blade tip angle for curved blade aerator.
Preview · Article · Dec 2009 · International journal of Environmental Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Paddle wheel aerators made of polyvinyl chloride (PVC) pipe had standard aeration efficiencies (SAE) of 2·0–2·6 kg O2 kWh−1 when paddle wheel diameter was 71–81 cm, paddle wheel speed was < 90 rev min−1, and paddle depth was < 15 cm. The standard oxygen transfer rate (SOTR) was low (1·15–1·85 kg O2 h−1 per 1-m length of paddle wheel). To supply enough oxygen for large ponds, PVC paddle wheels would be impractically long, and, even then, values for SOTR per unit length of paddle wheel and SAE would be lower than those obtained for steel paddle wheels currently used in aquaculture. PVC paddle wheels might have application in small ponds and especially in mariculture ponds where construction of noncorrosive material would be beneficial.
Full-text · Article · Dec 1988 · Aquacultural Engineering
[Show abstract][Hide abstract] ABSTRACT: An economic engineering approach was used to estimate total aeration cost and to generate average cost curves of aeration. Fixed and variable costs were estimated for 23 different electric and tractor powered aeration devices. Least-cost aeration devices were selected for varying pond sizes. Below about 250 h of aeration per season, tractor-powered aeration devices were more efficient economically. Above approximately 250 h of aeration, electric aerators were more efficient. However, for ponds less than 2 ha in size, the propeller-aspirator-pumps (1–3 hp) were the least-cost system. For pond sizes above 0·4 ha, electric floating paddlewheels generally were the most cost efficient.
No preview · Article · Jan 1989 · Aquacultural Engineering