C. A. Buckley

The effect of salts used in textile dyeing on microbial decolourisation of a reactive azo dye

Azo dyes account for 60 to 70% of all textile dyestuffs produced and are the most common chromophore of reactive textile dyes. Colouration of textile effluents usually can be linked to the presence of water-soluble (reactive) azo dyes. Under anaerobic conditions azo dyes can be used as terminal electron acceptors during microbial respiration, being reduced and decolourised concurrently with re-oxidation of reduced flavin nucleotides. Thus, the process of anaerobic digestion is under investigation as an effluent treatment option for the textile industry. The ability of anaerobic microbial consortia to decolourise azo dyes is well established; however, an additional factor that requires consideration is the high concentration of salts present in reactive dyeing effluent. Nitrate, sulphate, chloride and carbonate salts can all be used during reactive dyeing. This paper presents results of an investigation into the effect of nitrate and sulphate on the decolourisation of a reactive azo dye, Reactive Red 141. ...

The reuse of reactive dye liquors using charged ultrafiltration membrane technology

A closed-loop recycle system using a charged ultrafiltration membrane to decolourise reactive dye effluents from a textile yarn and fabric dyeing process is described. The economics of the process depend on the value of the electrolyte (

Reverse osmosis treatment and reuse of textile dyehouse effluents

5 to

The effect of pH on the nanofiltration of the carbonate system in solution

10 per M3). Conventional reactive dyeing technology was examined and modified to facilitate dye liquor reuse. The performance of the membrane was examined in terms of electrolyte rejection, colour rejection and permeate flux under varying conditions of solution pH, ionic strength and operating pressure.

Modelling of nanofiltration applied to the recovery of salt from waste brine at a sugar decolourisation plant

Abstract A 30 m 3 /d pilot-plant consisting of screening, alum coagulation, microfiltration reverse osmosis was operated for 2 years on cotton/nylon/polyester dyehouse effluents. The reverse osmosis modules used were the brackish and seawater UOP PA300 type. The pilot-plant operated at water recoveries of 85–95% and temperatures of 30–45°C. The microfiltration unit was used to remove suspended solids and colloidal dyestuffs from the effluent prior to the spiral-wrap membranes. The average permeate flux was 15 l/m 2 h and has been maintained by regular cleaning. The average permeate quality was 60 mg/l of T.D.S., 15 mg/l of sodium, 11 mg/l of TOC and 21 ADMI colour units. The product water was reused routinely for production dyeing.

Challenges with up-scaling dry sanitation technologies

Abstract The rejection and flux performance of a commercially available charged ultrafiltration membrane (also called a nanofiltration membrane) has been described for the sodium carbonate system in solution. The influence of pH on the speciation of the feed solution and on permeate composition has been examined. In addition, the implications of increased feed concentration on ion exclusion has been investigated. Furthermore, the application of nanofiltration for the removal of potential scale forming (precipitation fouling) compounds from carbonate solutions has been determined. The enhancement of the rejection of scale forming compounds by the addition of a sequestrant has also been determined. The influence of anion species on the rejection of sodium by nanofiltration membranes has been determined over a range of pH values by comparing the rejections of sodium ions in carbonate/bicarbonate systems in solution with the rejections of sodium ions in sulphate and chloride solutions. Finally, summarised pilot plant results for the regeneration and reuse of sodium hydroxide from caustic effluents have been presented. Nanofiltration has been applied as a pretreatment softening stage for the separation of sodium bicarbonate/carbonate from scale forming and organic impurities in this commercially viable effluent treatment sequence.

To what extent can portable fluorescence spectroscopy be used in the real-time assessment of microbial water quality?

Abstract The implementation of a computer model to simulate reverse osmosis in systems with several components is described. The model was based on the Spiegler-Kedem theory of reverse osmosis. The results of a pilot-scale investigation of the use of nanofiltration to recover sodium chloride from waste brine from the regeneration of anion exchange resin were used in this study. This effluent contains around 50 g/l of sodium chloride and 5 g/l (as total carbon) of organic colourants, many of which are negatively charged. When using the SelRO TM MPT-30 or MPT-31 membrane at an operating pressure of 3 MPa, temperatures between 45°C and 60°C, and linear feed flow rates around 1.6 m/s, the retention of sodium chloride was found to be between 0% and 20%, while the organic compounds had an overall retention of 80% to 97%. The experimental results were used to obtain a set of parameters relating to the system, which were then used to generate design data for a full-scale plant. Suitable module arrangements were proposed and the system performance for each case was predicted.

The nanofiltration and reuse of effluent from the caustic extraction stage of wood pulping

The acceleration of sanitation delivery towards meeting the South African Governments target of completely eradicating the existing backlogs by 2010, has led to a surge of activities. As part of its strategy for ensuring that basic sanitation is provided, the policy has recommended that a ventilated improved pit latrine (VIP) is considered as the basic minimum requirement in the form of a sanitation technology. The up-scaling and delivering of sanitation in many cases in the form of VIPs and its derivatives, as well as urine diversion technology are beginning to pose many technical challenges. The principles on which they have been designed are not always being observed in practice. As a result, some systems are filling up much faster than expected. Research has found that the breakdown in the faeces is not happening as would be expected in an anaerobic reactor, and that the drying of faeces in humid conditions, even with the use of drying agents, is not optimum. These problems, which are being experienced in the field, will have long term repercussions on the sustainability of sanitation provision. This paper aims to share these experiences and findings of research, and the impact it may have on the Sanitation MDG goals.

Dynamic membrane ultrafiltration and hyperfiltration for the treatment of industrial effluents for water reuse

The intrinsic fluorescence of aquatic organic matter emitted at 350 nm when excited at 280 nm correlates widely with water quality parameters such as biochemical oxygen demand. Hence, in sewage-impacted rivers and groundwater, it might be expected that fluorescence at these wavelengths will also correlate with the microbial water quality. In this paper we use a portable fluorimeter to assess the relationship between fluorescence intensity at this wavelength pair and Escherichia coli enumeration in contrasting river catchments of poor water quality: in KwaZulu-Natal, S. Africa and the West Midlands, UK. Across all catchments we demonstrate a log correlation (r = 0.74) between fluorescence intensity and E. coli over a seven-log range in E. coli enumerations on non-perturbed (unfiltered) samples. Within specific catchments, the relationship between fluorescence intensity and E. coli is more variable, demonstrating the importance of catchment-specific interference. Our research demonstrates the potential of using a portable fluorimeter as an initial screening tool for indicative microbial water quality, and one that is ideally suited to simple pollution scenarios such as assessing the impact of faecal contamination in river or groundwater at specific sites.

A critical review of experimental and predicted methane generation from anaerobic codigestion

Abstract One of the bleach stages in the treatment of wood for the manufacture of pulp is the extraction of lignin with sodium hydroxide. The resulting wash water is highly coloured at a pH of 7 to 10 and a conductivity of 4 to 7 mS/cm. The high colour precludes its reuse in the bleaching section of the pulping process. The use of nanofiltration for the removal of colour bodies from the effluent while allowing most of the inorganic salts to pass through the membrane is described. In particular, aspects such as pretreatment and membrane cleaning will be addressed.