RESUMO
An update on the current research and development of the treatment technologies, which utilize natural processes or passive components in wastewater treatment, is provided in this paper. The main focus is on wetland systems and their applications in wastewater treatment (as an advanced treatment unit or decentralized system), nutrient and pollutant removal (metals, industrial and emerging pollutants including pharmaceutical compounds). A summary of studies involving the effects of vegetation, wetland design and modeling, hybrid and innovative systems, storm water treatment and pathogen removal is also included.
Assuntos
Biodegradação Ambiental , Eliminação de Resíduos Líquidos/métodos , Áreas Alagadas , Metais/análise , Águas Residuárias/análise , Águas Residuárias/microbiologia , Poluentes Químicos da Água/análise , Poluição Química da Água/análise , Poluição Química da Água/estatística & dados numéricosRESUMO
This paper provides a review of the treatment technologies, which utilize natural processes or passive components in wastewater treatment. In particular, this paper primarily focuses on wetland systems and their applications in wastewater treatment (as an advanced treatment unit or decentralized system), nutrient and pollutant removal (single and multiple pollutants, and metals), and emerging pollutant removal (pharmaceuticals). A summary of studies involving the plant (vegetation) effects, wetland design and modeling, hybrid and innovative systems, storm water treatment and pathogen removal is also included.
RESUMO
Biological nitrogen removal is becoming a proven approach to reducing the total nitrogen discharged from wastewater treatment facilities. Simulation performed with intermittent aeration-type activated sludge process using Activated Sludge Model No. 1 predicted that up to 90% total nitrogen removal could be attained when the total cycle time and its anoxic phase were balanced adequately. This control limits electron donor and acceptor levels--ammonia-nitrogen (NH4(+)-N) in the aerobic phase and nitrate-nitrogen (NO3(-)-N) in the anoxic phase. Specifically, maximum nitrogen removal appears to be achieved with a 2- to 3-hour cycle time, during which, anoxic conditions were present for 40 to 50% of the time. A 10- to 16-hour hydraulic retention time appears adequate to achieve these results. The solids retention time studied was between 15 and 25 days, as this range was deemed sufficient to establish the nitrifying organism population in most applications. Predictions indicate that the conventional activated sludge system can be retrofitted for better nitrogen management at the treatment plants.
Assuntos
Simulação por Computador , Nitrogênio/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , Amônia/química , Modelos Químicos , Oxigênio/química , Fatores de Tempo , Água/químicaRESUMO
The kinetics of Escherichia coli inactivation using ozone and ultraviolet (UV) radiation, separately and simultaneously, was evaluated at 25 degrees C in buffered (pH 6.0, 7.0 and 8.0), demand-free media. While ozone was found to be a stronger disinfectant than UV radiation, using both simultaneously was more effective than using them individually. Inactivation kinetics was pseudo first-order for the three treatment processes, while the disinfection rate was a linear function of the disinfectant dose. The synergism observed in microbial inactivation when the disinfectant processes were combined was illustrated by estimates of kinetic model parameters. This synergy was attributed to the generation of hydroxyl radicals via ozone photolysis. Subsequently, dosage calculations, as based on disinfectant level and exposure time, indicated that the simultaneous use of UV and ozone could substantially reduce their individual doses.
