The optimisation of ultrasonic cleaning procedures for dairy fouled ultrafiltration membranes

Ultrafiltration (UF) of whey is a major membrane based process in the dairy industry. However, commercialization of this application has been limited by membrane fouling, which has a detrimental influence on the permeation rate. There are a number of different chemical and physical cleaning methods currently used for cleaning a fouled membrane. It has been suggested that the cleaning frequency and the severity of such cleaning procedures control the membrane lifetime. The development of an optimal cleaning strategy should therefore have a direct implication on the process economics. Recently, the use of ultrasound has attracted considerable interest as an alternative approach to the conventional methods. In the present study, we have studied the ultrasonic cleaning of polysulfone ultrafiltration membranes fouled with dairy whey solutions. The effects of a number of cleaning process parameters have been examined in the presence of ultrasound and results compared with the conventional operation. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath. Results show that ultrasonic cleaning improves the cleaning efficiency under all experimental conditions. The ultrasonic effect is more significant in the absence of surfactant, but is less influenced by temperature and transmembrane pressure. Our results suggest that the ultrasonic energy acts primarily by increasing the turbulence within the cleaning solution.

The use of ultrasonic cleaning for ultrafiltration membranes in the dairy industry

The ultrafiltration of whey solutions is a common feature of dairy processes. However, the frequent fouling of ultrafiltration membranes and the subsequent cleaning cycle significantly affect the economics of such a process. In this work, we investigated the effect of ultrasonics on the cleaning of whey-fouled membranes and examined the variables that influence this effect. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath.

Results show that the use of ultrasonics enhances the flux recovery following fouling. The extent of flux recovery is independent of the length of sonication time and increases with ultrasonic power. The use of surfactants in combination with ultrasonic irradiation shows a synergistic effect, providing a better efficiency than either cleaning process alone. Repetitive use of ultrasonic cleaning over a 1 month period does not result in any significant change in the permeate flux of a cleaned membrane, indicating that the ultrasonic treatment does not appear to damage the membrane structure itself.

Power ultrasound offers an environmentally friendly approach to cleaning dairy UF membranes

Flat sheet polymeric UF membranes of 30000 MWCO were obtained from Millipore Inc. Polypropylene spacers of a 50 mil (1.3 mm) thickness were obtained from KOCH membrane systems. A single 30 cm^sup 2^ membrane sheet was sandwiched with a spacer on the feed side of a cross flow Minitan S unit (Millipore Inc). The unit was immersed in a 50 kHz ultrasonic bath that was switched on as required. All experiments used re-constituted spray-dried whey powder to foul the membrane.

Study into the ultrasonic cleaning of wool

This research studied the use of ultrasonic irradiation during wool cleaning with an aim to improve the cleaning process and reduce its impact on the environment. The research found that ultrasonic cleaning reduced energy, detergent and chemicals consumption, reduced fibre entanglement and had no significant effect on fibre properties.

Effect of operating parameters and cleaning on the performance of ceramic membranes treating partially clarified sugar cane juice

The performance of ceramic membranes with pore sizes of 0.05 and 0.10 mm in purifying limed and partially clarified sugar cane juice was investigated under different operating conditions. From various operating conditions and strategies, switching off the permeate for 5 seconds for every 5 minutes (S5sT5 m) by an automated control valve provided higher flux. From the three pH experiments conducted on the 0.05 mm membrane, the best performance was observed at a pH of 7.5. Amongst the four fouling models tested, the cake filtration model fitted the performance of both membranes with higher accuracy at a transmembrane pressure of 0.5 bar. Filtering the cane juice through the membrane reduced the turbidity by 99.7%, color by 15%, and the starch concentration by 80% as well as increased the purity by 1.4%. The effective cleaning chemical composition from experimental results showed that 1% NaOH and 3000 ppm NaOCl solution performed the best but only for the experiments that were treating limed and partially clarified juice at pH 7.5.

Restructuring the architecture of state regulation in the Australian and Aotearoa/New Zealand cleaning industries and the growth of precarious employment

This paper examines changes in the commercial cleaning industry in Australasia which are occurring against a backdrop of significant transformation in the mode of labour market regulation in both countries. Specifically, whereas for most of the twentieth century both Aotearoa/New Zealand and Australia had systems of labour market regulation in which the state provided minimum wage and work protections through the interventions of arbitration courts, in the past few years these courts have either been abolished (in the case of New Zealand) or severely restricted in their ambit (in the case of Australia), all as part of a neoliberal effort to introduce “flexibility” into labour markets. The result has been an erosion of wages and a worsening of conditions of employment for cleaners and many other groups of workers. At the same time, this transformation in the architecture of labour market regulation poses significant challenges to unions seeking to represent cleaners and other low-paid service sector workers.

On the mopfloor: researching employment relations in the hidden world of commercial cleaning

This chapter explores some of the challenges and tribulations of studying the hidden and hitherto unresearched world of work in the New South Wales (Australia) cleaning industry. The findings and analysis presented here are informed by my research into employment relations, labour management and the organisation of work in the NSW commercial cleaning industry (Ryan, 2007). This research used primarily a case study of an industry exemplar, and made extensive use of participant observation to obtain evidence on the perceived realities of work and organisation for those on the front line of cleaning work - the cleaners and their supervisors - and to understand how they make sense of their working world. The discussions and findings presented in this chapter support the use of an ethnographic approach to work, and provide some guidance as to how a participant observation study might be carried out and what might be found through the use of this method.

When is a team a team? 'Teamworking' and the reorganisation of work in commercial cleaning

Purpose – The article seeks to analyse and explore the contradictions and variations in the concepts “team” and “teamwork” and their use in the NSW, Australia, commercial cleaning industry.

Design/methodology/approach – The article utilises an ethnographic study of a large Australian cleaning firm. Data were collected using participant observation, field notes, and interviews with managers.

Findings – The study provides evidence for the limited uptake of the idealised form of teamwork in commercial cleaning and suggests that teamworking is another means of coordinating groups of workers. Furthermore, the findings support previous research into the paradox of teams without teamwork.

Originality/value – The research provides an insight into the largely neglected area of the reorganisation of work in commercial cleaning. It also provides a critique of the concept of teams and teamworking.