L.R. Weatherley

Ammonia removal from wastewater by ion exchange in the presence of organic contaminants.

The scope of this study was the removal of ammonium by ion exchange from simulated wastewater. The study looks at the effect of organics upon ammonium ion exchange equilibrium uptake. The ion exchangers included a natural zeolite clinoptilolite, and two polymeric exchangers, Dowex 50w-x8, and Purolite MN500. The organic compounds studied included citric acid and a number of proteins. The traditional method for removal of ammonium and organic pollutants from wastewater is biological treatment, but ion exchange offers a number of advantages including the ability to handle shock loadings and the ability to operate over a wider range of temperatures. The results show that in most of the cases studied, the presence of organic compounds enhances the uptake of ammonium ion onto the ion exchangers.

Biological activated carbon treatment of industrial wastewater in stirred tank reactors

The industrial effluent under investigation was the simulated aqueous discharge from a carpet printing plant in Northern Ireland, comprising of a ternary solution of acid dyes. This effluent was investigated using the biological activated carbon (BAC) process for colour removal in an aerobic stirred tank reactor configuration. The following systems were experimentally investigated: bacteria immobilised on granular activated carbon (GAC); bacteria immobilised on sand particles; GAC (with no biological activity) and free bacterial cells. The bacterium used in this study was Pseudomonas putida (NCIMB 9776) and the activated carbon was Filtrasorb 400. Ternary dye concentrations were determined by spectrophotometry. Results indicated that BAC system outperformed the combination conventional GAC and biological water treatment processes. For biodegradable anthraquinone dyes, this enhanced colour removal was due to higher dye utilisation rates caused by the increase in substrate concentration at the granule surface found in BAC systems. For non-biodegradable azo dyes, increased biosorption was found in BAC systems compared to conventional immobilised systems.

Biodegradation and biosorption of acid anthraquinone dye

The acid anthraquinone dye Tectilon Blue (TB4R) is a major coloured component from the aqueous effluent of a carpet printing plant in Northern Ireland. The aerobic biodegradation of TB4R has been investigated experimentally in batch systems, using three strains of bacteria, namely, Bacillus gordonae (NCIMB 12553), Bacillus benzeovorans (NCIMB 12555) and Pseudomonas putida (NCIMB 9776). All three strains successfully decolourised the dye, and results were correlated using Michaelis-Menten kinetic theory. A recalculation of the reaction rate constants, to account for biosorption, gave an accurate simulation of the colour removal over a 24-h period. Up to 19% of the decolorisation was found to be caused by biosorption of the dye onto the biomass, with the majority of the decolorisation caused by utilisation of the dye by the bacteria. The reaction rate was found to be intermediate between zero and first order at dye concentrations of 200-1000 mg/l.

The effect of reaction conditions upon lipase catalysed hydrolysis of high oleate sunflower oil in a stirred liquid–liquid reactor

Abstract This study is concerned with the hydrolysis of sunflower oil in the presence of lipase from the yeast Candida rugosa . The rate of reaction was studied as a function of lipase concentration and as a function of oil:water ratio. The sequential batchwise addition of water in a batch reactor as a means of controlling glycerol concentration in the reaction mixture has been studied. The potential benefits in terms of improved overall reaction kinetics and final conversion for a process are quantified. The effect of reaction products on the downstream separation of the liquid–liquid product mixture is also quantified, and the experimental relationships between coalescence rate, oleic acid concentration and glycerol concentration are presented. A novel technique to estimate the selective accumulation of enzyme at the liquid–liquid interface is described and confirms significant enhancement of enzyme activity in the vicinity of the interface.

Textile Wastewater Treatment Using Granular Activated Carbon Adsorption in Fixed Beds

This work involved the treatment of industrial wastewater from a nylon carpet printing plant which currently receives no treatment and is discharged to sea. As nylon is particularly difficult to dye, acid dyes are required for successful coloration and cause major problems with the plants effluent disposal in terms of color removal. Granular activated carbon Filtrasorb 400 was used to treat a ternary solution of acid dyes and the process plant effluent containing the dyes in a fixed-bed column system. Experimental data were correlated using the bed depth service time (BDST) model to previously published work by the authors for single dye adsorption. The results were expressed in terms of the BDST adsorption capacity, in milligrams of adsorbate per gram of adsorbent, and indicated that there was a 12-25% decrease in adsorption capacity in the ternary system compared to the single component system. This reduction has been attributed to competitive adsorption occurring in the ternary component system. Dye adsorption from the process plant effluent showed an approximate 65% decrease in adsorption capacity compared to the ternary solution system. This has been attributed to interference caused by the other colorless textile effluent pollutants found in the process wastewater. A chemical oxygen demand analysis on these components indicated that the dyes accounted for only 14% of the total oxygen demand.

Modelling of mass transfer from falling droplets

Abstract The prediction of mass transfer rates to and from moving drops has traditionally used the Whitman two-film theory approach in which the resistances to mass transfer on each side of the interface are described by film mass transfer coefficients. These are correlated in terms of the hydrodynamic conditions, the physical properties of the fluids, and the geometry of the system. The performance of liquid–liquid contactors in which mass transfer occurs between swarms of moving droplets of one phase and the other liquid phase as the continuous phase, has similarly been correlated in terms of mass transfer coefficients. These lump together the combined effects of interfacial mass transfer resistances and those associated with the bulk phases, the effects of interfacial disturbances, coalescence and break-up phenomena, specific surface area, and the effects of axial mixing. In this paper we build upon earlier work and other published research which uses finite element methods to quantitatively calculate flow field data and trajectory predictions for single particles and drops in a two phase system. The differential equations were discretised using the finite element approach employing a procedure based on the Lagrangian framework developed earlier. Here we extend the approach to calculate mass transfer rates between single aqueous drops and a continuous immiscible solvent phase. The calculated values of drop velocity and mass transfer rates are compared with experimental values determined for single drops of ethanol/water mixtures extracting into a continuous phase of n-decanol. Good agreement between the experimental and predicted values was obtained, thus demonstrating that in this case, interfacial mass transfer in liquid–liquid systems can be predicted from the fundamental transport equations. The results of the work indicate the potential of further development of this approach for swarming drops and hence quantitative prediction of the behaviour of liquid–liquid contactors.

Co-digestion of solid poultry manure with municipal sewage sludge

The anaerobic digestion was investigated using mixed sewage sludge and poultry manure. The experiments showed that a 30% addition of poultry manure to the sewage sludge did not increase specific gas yield (376 dm(3)/kg VS versus 384 dm(3)/kg VS), however gas production rate as calculated per unit volume was 1.5 higher for sludge and manure mixture. The anaerobic digestion turned out to be inefficient in terms of pathogen treatment, since the reduction of Enterobacteriaceae reached only two logarithmic units. In the course of the digestion processes, nutrients were released to the supernatant, and longer SRT favored that phenomenon. The liquor after the digestion of sludge alone was rich in phosphates (348-358 gP/m(3)) and contained a lot of organic carbon (COD of 2705-6034 gO2/m(3)). Conversely, more ammonium nitrogen was found in the supernatant after co-digestion of sludge with manure (2094-2221 gN/m(3)). However, there was no evidence of ammonia inhibition.

COD removal from textile industry effluent: pilot plant studies

Abstract This work involved the treatment of industrial waste water from a nylon carpet printing plant. As dyeing of nylon is particularly difficult, acid dyes, fixing agents, thickeners, finishing agents, are required for successful colouration and cause major problems with the plant’s effluent disposal in terms of chemical oxygen demand (COD). Granular activated carbon (GAC) Filtrasorb 400 was used to treat a simulated process plant effluent containing all the pollutants. Equilibrium isotherm experiments were established and experimental data obtained showed good empirical correlation with Langmuir isotherm theory. Column experimental data, in terms of COD were correlated using the bed depth service time (BDST) model. Solid phase loading in the columns were found to approach that in equilibrium studies indicating an efficient use of adsorbent. The results from the BDST model were then used to design a pilot adsorption rig at the plant. The performance of the pilot plant column were accurately predicted by scale-up from the bench scale columns.

PREDICTION OF BISOLUTE DYE ADSORPTION ISOTHERMS ON ACTIVATED CARBON

The removal of acid dyes, Tectilon Blue 4R, Tectilon Red 2B and Tectilon Orange 3G, from single solute, bisolute and trisolute solutions by adsorption on activated carbon (GAC F400) has been investigated in isotherm experiments. Results from these experiments were modelled using the Langmuir and Freundlich adsorption isotherm theories with the Langmuir model proving to be the more suitable. The Ideal Adsorbed Solution (IAS) model was coupled with the Langmuir isotherm to predict binary adsorption on the dyes. The application of the IAS theory accurately simulated the experimental data with an average deviation of approximately 3% between modelled and experimental data.

Particle and droplet trajectories in a non-linear electrical field

Abstract In this paper we describe a new approach in which finite element analysis is applied to predict charged particle trajectories in a liquid continuum across which a non-linear electrical field is applied. The equations of motion and equations describing the distribution of the electrical field in the entire contactor are solved simultaneously and thus yield the trajectories of individual particles emerging from a single charged nozzle. The predictions are compared with experimentally determined trajectories and good agreement is demonstrated. The work is regarded as a starting point for the quantitative description of charged droplet motion in a liquid–liquid contactor and the associated prediction of droplet hold-up and mass transfer using a similar approach.