RESUMO
Previous research has demonstrated that powdered activated carbon (PAC), when applied at very low dosages and long SRTs, reduces membrane fouling in membrane bioreactors (MBRs). This effect was related to the formation of stronger sludge flocs, which are less sensitive to shear. In this contribution the long-term effect of PAC addition was studied by running two parallel MBRs on sewage. To one of these, PAC was dosed and a lower fouling tendency of the sludge was verified, with a 70% longer sustainable filtration time. Low PAC dosages showed additional advantages with regard to oxygen transfer and dewaterability, which may provide savings on operational costs.
Assuntos
Reatores Biológicos/normas , Carvão Vegetal/química , Membranas Artificiais , Incrustação Biológica , Análise da Demanda Biológica de Oxigênio , Compostos Orgânicos/isolamento & purificação , Projetos Piloto , Polímeros/isolamento & purificação , Polissacarídeos/análise , Pós , Proteínas/análise , Esgotos/química , Viscosidade , Poluentes Químicos da Água/isolamento & purificaçãoRESUMO
The feasibility of a high-loaded membrane bioreactor to improve methane recovery from sewage was investigated. Although the process needs further optimization, it already is feasible to recover at least 35% of the sewage COD. Important aspects for further research are the occurrence of membrane fouling, and the optimum process conditions for bioflocculation, i.e. the proper SRT/HRT ratio, dissolved oxygen concentration and shear and overall energy production and consumption under optimised conditions.
Assuntos
Fontes de Energia Bioelétrica , Reatores Biológicos , Esgotos , Conservação de Recursos Energéticos , Membranas Artificiais , Purificação da Água/métodosRESUMO
Previous research had demonstrated that powdered activated carbon (PAC), when applied at very low dosages and long SRTs, reduces membrane fouling in membrane bioreactor (MBRs). In this contribution several mechanisms to explain this beneficial effect of PAC were investigated, including enhanced scouring of the membrane surface by PAC particles, adsorption of membrane foulants by PAC and subsequent biodegradation and a positive effect of PAC on the strength of the sludge flocs. It was concluded that the latter mechanism best explains why low dosages of PAC significantly reduce membrane fouling. Cheaper alternatives for PAC may have a similar effect.
Assuntos
Incrustação Biológica/prevenção & controle , Reatores Biológicos , Carvão Vegetal/química , Membranas Artificiais , Adsorção , Coloides , Filtração , Floculação , Tamanho da Partícula , Projetos Piloto , Pós , Esgotos/química , SolubilidadeRESUMO
The addition of a low concentration of PAC (0.5gL(-1) of sludge, i.e. a dose of 4mgL(-1) of wastewater), in combination with a relatively long SRT (50 days), to improve membrane filtration performance was investigated in two pilot-scale MBRs treating real municipal wastewater. Continuous filterability tests at high flux showed the possibility to run for 18h at 72Lm(-2)h(-1) and 180h at 50Lm(-2)h(-1), while significant fouling occurred without PAC. In addition, measurements of the critical flux showed an increase of 10% for this strategy. Low dosage and high retention time makes it feasible and cost effective. Further advantages with regard to permeate quality and possible micropollutants removal are currently under investigation.
