Este trabalho objetivou analisar a relação entre os nutrientes fósforo total (P) enitrogênio total (N) e a clorofila a (Cla) em um pequeno açude urbano e em açudesrurais. Realizou-se a análise dos parâmetros de qualidade da água em um açudelocalizado em Fortaleza (CE), por meio de estudo de campo, além do levantamentodo histórico de monitoramento dos mesmos parâmetros em 35 açudes rurais,no semiárido do Nordeste brasileiro, no estado do Ceará. Geraram-se correlaçõesempíricas entre os nutrientes e o fitoplâncton. Posteriormente, analisaram-secenários de redução das cargas de nutrientes com a aplicação de um modelode qualidade da água de mistura completa, cujo coeficiente de decaimento doP é para regiões semiáridas, e das equações empíricas obtidas. Verificou-se queP melhor descreveu a concentração de Cla em todos os açudes, com o ajustede equações do tipo potência. As concentrações de P no açude urbano foramsuperiores às dos demais açudes, com uma média de 1,76 mg/L e a relação N:Pem torno de 1; nos açudes rurais, as concentrações médias variaram entre 0,04e 0,59 mg/L e a relação N:P variou entre 5 e 50. A análise dos cenários mostrouque diferentes níveis de redução da carga de P poderiam ser adotados em funçãode distintas metas de redução das concentrações de P e Cla. Concluiu-se que osmodelos propostos são aplicáveis e constituem ferramentas úteis de auxílio àtomada de decisão na gestão dos recursos hídricos.
The present study evaluated the impact of hydrological variability on the hydrodynamics of an urban lake in Brazil, considering water quality dynamics and its effects on evaporation. The Storm Water Management Model (SWMM) was applied to the lake basin, and the two-dimensional model CE-QUAL-W2 was used to simulate the hydrodynamics and lake evaporation. The two models were coupled to carry out the integrated basin-lake modeling. Then, two water quality models were applied: a transient complete mixing model and an empirical model based on wind speed. Time series of total phosphorus (TP) were generated, and empirical correlations between TP and hydrological variables were proposed. Modeled TP and measured biochemical oxygen demand (BOD) were correlated with monthly Class A pan coefficients (K) adjusted for the lake. The K-values were negatively correlated with TP modeled by the complete mixing model (R2 = 0.76) and the empirical model (R2 = 0.52), as well as by BOD measurements (R2 = 0.85). This indicates that water pollution attenuates evaporation rates. Scenarios of lake pollution and level reduction due to evaporation were also analyzed. The results from this study are important to improve the management of lakes and reservoirs by including the impact of pollution on the water balance.
Discharge of wastewater contained high amount of nitrogen would cause eutrophication to water bodies. Simultaneous nitrification and denitrification (SND) has been confirmed as an effective process, the isolation of SND bacteria is crucial for its successful operation. In this study, an SND strain was isolated and identified as Pseudomona aeruginosa LS82, which exhibited a rapid growth rate (0.385 h−1) and good nitrogen removal performance (4.96 mg N·L−1·h−1). Response surface methodology was applied to optimize the TN removal conditions, at which nearly complete nitrogen (99.8 ± 0.9%) removal were obtained within 18 h at the condition: pH 8.47, 100 rpm and the C/N ratio of 19.7. The saddle-shaped contours confirmed that the interaction of pH and inoculum size would influence the removal of total nitrogen significantly. Kinetic analyses indicated that the reduction of nitrite was the rate-limiting step in the SND process. Our research suggested strain LS82 can serve as a promising candidate for the treatment of ammonium rich wastewater, and expended our understanding the nitrogen removal mechanism in the SND process.
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