Search PubMed⌕ Search

PubMed · 11730133

Future perspectives in bioreactor development.

Abstract

The paper discusses conversion capacities of both anaerobic and aerobic wastewater treatment systems in relation to growth kinetics, hydrodynamics and biomass concentration. In the current modern anaerobic high-rate reactors the conversion potentials are optimally exploited. This is not yet true for aerobic systems since operation of aerobic systems under conditions of low biomass growth reduces the maximum applicable loading rates significantly. Both the concept of granulation and the introduction of fluidised bed systems have increased conversion capacities for both anaerobic and aerobic systems significantly. One of the latest development concerns the SBR with granular biomass. The grazing concept, in which ciliates convert aerobically grown dispersed cells, offers a possibility for significant improvement of aerobic systems. In the fields of psychrophilic and thermophilic anaerobic treatment, specific reactor development may contribute to further enhance volumetric conversion capacities. Due to reduced water usage, both COD and salt concentrations tend to increase for industrial effluents. As a consequence, there is a need for the development of anaerobic reactors retaining flocculant biomass. The membrane bioreactors offer a solution for certain niches in wastewater treatment. However the oxygen transfer economy is poor. There is a need for fundamental knowledge development to obtain a realistic image of this technology.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

R Mulder, T L Vereijken, C T Frijters, S H Vellinga. 2001. Future perspectives in bioreactor development.. https://pubmed.ncbi.nlm.nih.gov/11730133/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Multipopulation model of membrane-aerated biofilms.

Biofilms cultivated on oxygen-filled gas-permeable membranes grow differently than conventional biofilms, as the chemical species required for growth diffuse from different sides of the biofilm. Oxygen is delivered directly to the base of the biofilm by the membrane, while organic substrates and other soluble nutrients are provided to the upper surface of the biofilm via the water in which the membranes are immersed. This counterdiffusion of nutrients results in a growth environment very different from that of conventional biofilms that receive both oxygen and other nutrients from the water. In recent years, membrane-supported biofilms have been shown to simultaneously remove chemical oxygen demand (COD) and inorganic nitrogen from wastewater in laboratory studies. Several investigators have developed computer models of these biofilms, but they have all focused on a single population of aerobic bacteria. While these models are useful in characterizing the behavior of these biofilms in pure cultures, they are not useful in modeling the behavior of the biofilms in mixed cultures such as those found in wastewater treatment. In this study, a multipopulation biofilm model was developed that includes aerobic heterotrophs, nitrifiers, denitrifiers, and acetoclastic methanogens. The model was constructed with Aquasim software and can predict the COD and inorganic nitrogen removal behavior observed previously in experimental studies. In this paper we present examples of predicted biofilm behavior and compare the results of this multiple-population model with the single-population models published previously. In addition, the behavior of the biofilm is discussed in terms of application to wastewater treatment.

Bacteria, Aerobic↗

Fluorotelomer alcohol biodegradation yields poly- and perfluorinated acids.

The widespread detection of environmentally persistent perfluorinated acids (PFCAs) such as perfluorooctanoic acid (PFOA) and its longer chained homologues (C9>C15) in biota has instigated a need to identify potential sources. It has recently been suggested that fluorinated telomer alcohols (FTOHs) are probable precursor compounds that may undergo transformation reactions in the environment leading to the formation of these potentially toxic and bioaccumulative PFCAs. This study examined the aerobic biodegradation of the 8:2 telomer alcohol (8:2 FTOH, CF3(CF2)7CH2CH2OH) using a mixed microbial system. The initial measured half-life of the 8:2 FTOH was approximately 0.2 days mg(-1) of initial biomass protein. The degradation of the telomer alcohol was monitored using a gas chromatograph equipped with an electron capture detector (GC/ECD). Volatile metabolites were identified using gas chromatography/ mass spectrometry (GC/MS), and nonvolatile metabolites were identified and quantified using liquid chromatography/ tandem mass spectrometry (LC/MS/MS). Telomer acids (CF3(CF2)7CH2COOH; CF3(CF2)6CFCHCOOH) and PFOA were identified as metabolites during the degradation, the unsaturated telomer acid being the predominant metabolite measured. The overall mechanism involves the oxidation of the 8:2 FTOH to the telomer acid via the transient telomer aldehyde. The telomer acid via a beta-oxidation mechanism was furthertransformed, leading to the unsaturated acid and ultimately producing the highly stable PFOA. Telomer alcohols were demonstrated to be potential sources of PFCAs as a consequence of biotic degradation. Biological transformation may be a major degradation pathway for fluorinated telomer alcohols in aquatic systems.

Bacteria, Aerobic↗

Activated sludge encapsulation in gellan gum microbeads for gasoline biodegradation.

A two-phase dispersion technique, termed emulsification-internal gelation, is proposed for encapsulation of activated sludge in gellan gum microbeads. The influence of emulsion parameters on size distribution of microbeads was investigated. Mean diameter of microbeads varied within a range of 34-265 microm as a descending function of emulsion stirring rate (1,000-5,000 rpm), emulsification time (10-40 min), and emulsifier concentration (0-0.1% w/w), and as an ascending function of disperse phase volume fraction (0.08-0.25). Encapsulated sludge expressed a high biodegradation activity compared with non-encapsulated sludge cultures even at 4.4 times lower level of overall biomass loading. Over 90% of gasoline at an initial concentration of 35 and 70 mg l(-1) was removed by both encapsulated and non-encapsulated sludge cultures in sealed serum bottles within 7 days. Encapsulation of activated sludge in gellan gum microbeads enhanced the biological activity of microbial populations in the removal of gasoline hydrocarbons. The results of this study demonstrated the feasibility of the production of size-controlled gellan gum-encapsulated sludge microbeads and their use in the biodegradation of gasoline.

Bacteria, Aerobic↗