Phytoplankton and physicochemical parameters in stabilization pond (Trindade, GO)

The Wastewater Treatment Plant (WWTP) of Trindade (16 ° 39'09'' S and 49 ° 31'50'' W), also known as Barro Preto WWTP, consists of preliminary treatment followed initially by three modules in parallel (A, B and C), each containing one anaerobic pond, one facultative pond and one maturation pond in series (Australian system), being the effluent released in the stream Barro Preto. The WWTP began operating in 1997 and had the final plan in 2011. This study aimed to evaluate treatment efficiency and the module based on algal community structure and physico-chemical variables during a period of six months (September, October, November, December 2010 and April and May 2011), which contains the dry and rainy periods. Were analyzed in reference to the structure and dynamics of algae: biomass, density, richness, diversity, equality, abundance and dominance; for physic-chemical analysis were: flow rate, wastewater temperature, depth, euphotic zone, HDT, pH, DO, CND, TP, PO4 -3, NH4 +, NO3, DOB5 20°C, COD, TSS, FSS, VSS and also climatic variables. The algae were collected through non-selective process (Van Dorn bottle). The samples abiotic, chlorophyll a and pheophytin were processed according to APHA, and the density algal by the Utermöhl method. Principal Component Analysis (PCA) were performed to characterize the physic-chemical processes and the spatial and temporal differentiation. It was also made a Canonical Correspondence Analysis (CCA). The facultative and maturation ponds shown to be influenced by the seasonality of the region, and presented variance in depth. In average, the module A showed an efficiency of COD removal of 45%, and optimal efficiency in removing DBO5 20°C (84%). The facultative pond showed the highest mean of PO4 -3 efficiency removal (48%), NH4 + (36%) NO3 - (44%), BOD5 20°C (74%). OD profile of type clinograde and thermal stratification was recorded in three months of collection. The maturation pond showed higher mean removal efficiency of PT (27%) and COD (19%). In just two months was recorded thermal stratification, and found clinograde profile throughout the study. The ponds presented one of the largest ever recorded phytoplankton densities in stabilization ponds and 170 taxa recorded throughout the study, being 40% of cyanobacteria are potentially toxic. The most abundant species in both ponds and throughout the study were Chlorella vulgaris, Chlorella minutissima, Closteriopsis acicularis, Merismopedia tenuissima, Synechococcus sp and Synechocysitis sp (dominant). The ponds presented according to the indices, low species diversity and low beta diversity. The beta diversity showed that the maturation pond has more flexibility in the rainy season and optional in the dry season. The canonical correspondence analysis (CCA) showed the most abundant species when best developed in seasonality. C. acicularis in the rainy season, C. minutissima in the end of the rainy season and the beginning of the dry season, M. tenuissima in late dry season, C. vulgaris and Synechococcus sp in late dry season and beginning of precipitation. This analysis showed which environmental variables can also influence the in distribution of species.