Avaliação da influência de chicanas e das estruturas de entrada e saída no desempenho de lagoas de estabilização.

Abstract

The aim of this master dissertation was to describe the operational performance of four pilotscale independently loaded primary facultative ponds, named F2?, F28, F29 and F30, treating wastewater predominantly domestic from sewerage of Campina Grande City (7° 13' 11" South, 35° 52' 31" West, 550m above m.s.l), Paraiba state, northeast Brazil. Ponds were operated at Experimental Station for the Biological Treatment of Sewage of the Federal University of Campina Grande (EXTRABES-UFCG), being F27 and F30 provided with, respectively, three and five parallel baffles, forming, respectively, four and six channels, F29 provided with a round-corner-baffle was, in fact, a long channel of 75 m and F2x was maintained without baffles as a control. Each 2.3 m deep-pond, being about 25 m long and 7.1 m width, had a hydraulic retention time of 15 days, and was fed with a flow rate of about 28 mVday, being the mean aerial organic loading in the range 370-380 kgBODj/ha.day. Each channel of F27 and F30 was fed with, respectively, one fourth and one sixth of the flow rate, the channel of F29 was fed with the totality of flow rate and the flow rate of pond F28 was divided into four parts in order to distribute it uniformly throughout the front wall of the pond. Raw wastewater was discharged at a level 50 cm deep below water surface and the effluent was collected from a level 50 cm above the bottom of the pond. Grab samples of raw sewage, taken from a trunk crossing the site of the experimental station, and pond effluents, taken from the outlet pipe of each reactor, were collected at 8 a. m., weekly, between August 2005 and July 2006, and analyzed for BOD5 , COD, suspended solids (SS), dissolved oxygen (DO), pH, temperature (T) and chlorophyll "a" (CLA). Control reactor tended to show lesser removal performances in terms of BOD (74%), COD (50%), and SS (62%), than baffled ponds (75-76% for BOD, 56-57% for COD and 70-71% for SS), but the one factor-ANOVA demonstrated that differences in terms of BOD, COD, DO, pH and T were not significant at a level of 5%. Mean concentrations of CLA and SS in the effluent of pond F2? were significantly less than those for other ponds. It was concluded that the physical modifications introduced in the design of the primary facultative ponds investigated herein were not enough to cause a more important difference in the average performance of a stabilization pond at such a level of treatment.