Font Size: a A A

Effects Of Carbon-based Nano-materials On Activated Sludge Process

Posted on:2013-02-01Degree:MasterType:Thesis
Country:ChinaCandidate:H X GuoFull Text:PDF
GTID:2231330377460515Subject:Biochemical Engineering
Abstract/Summary:PDF Full Text Request
With rapid social and economic development, carbon-based nanomaterialshave been widely used in industrial and commercial areas. The potential influencesof carbon-based nanomaterials on human health and ecological environment havereceived great concerns from both scientists and governments. Biological treatmentprocess, is most widely used for wastewater treatment. Carbon-based nanomaterialscould migrate into environmental media and thus been found in wastewatertreatment system, if they are released into the environment. Therefore, it is of vitalimportance to evaluate the impact of carbon-based nanomaterials on activatedsludge process.In this thesis, effects of two kinds of nano-materials including C60andsingle-walled nanotubes on the microbial aspects in wastewater treatment systemwere systematically studied. Biochemical characteristic and performance of thereactor, interaction between carbon-based nanomaterials and the activated sludge,were investigated. Main contents and result are as follows:1. To investigate the potential effects of carbon-based nanomaterials onwastewater treatment process, aqueous suspension of fullerene C60was added tosequencing batch reactors. The biochemical characteristics and bacterialcommunity structure of the activated sludge after treated for6hours were studiedand compared with the untreated control. For all reactors, the oxygen uptake ratesfirstly increased abruptly, then held for a short time and decreased rapidly followedby a slow decrease, finally kept stable at the background level. Results show thatthe oxygen uptake rates were not affected significantly by C60aqueous suspension.At the same time,95.5%of the ammonia nitrogen was removed by the activatedsludge for both treated and control rectors. The total organic carbon removal ratewas67.7%and66.7%for the treated and the control reactors, respectively. Theseresults show that C60aqueous suspension have no adverse effects on NH3-N andtotal organic carbon (TOC) removal when treated for a short time. The profiles ofPCR-DGGE analysis show diverse bacterial community composition in theactivated sludge and no significant changes in community structure after treatedwith C60aqueous suspension for a short time. 2. Respiration inhibition induced by SWNTs to activated sludge wasinvestigated using standard method established by Environmental ProtectionAgency combined with instrumental analysis. Varying degree of respirationinhibition was observed for the activated sludge added with differentconcentrations of SWNTs. The effect of SWNTs addition on the metabolism ofactivated sludge was also evaluated. Most of souble microbial products wereadsorbed by SWNTs. Polysaccharide and protein in aquatic systems can interactstrongly with canbon nanotubes. The settleability was also significantly effected bySWNTs. Yet, the performances of activated sludge reactor was not effected.3. The thermodynamics and dynamics of adsorption of extracellular polymericsubstances (EPS) onto single-walled carbon nanotubes (SWNTs) were studied. Theadsorption process of EPS could be described by the Lagergren dynamical modeland Langmuir adsorption model. The surface and the gap, internal interspace ofSWNTs was effective adsorptive sites. We proposed that the strong adsorptiveinteraction between EPS and SWNTs was due to the π-π electron-donor-acceptor(DEA) interaction between EPS and SWNTs. Hydrogen bonding interactionbetween EPS could reduce staric hindrance which was available for adsorption.Such an interaction was greatly influenced by the solution pH and the optimum pHvalue was5-7.
Keywords/Search Tags:carbon-based nanomaterials, activated sludge, extracellular polymericsubstances, adsorption, respiration inhibition
PDF Full Text Request
Related items