Application of floating medium filters for aquaculture wastewater treatment

Filtration is an effective process in removing particles of various nature and sizes that are present in water and wastewater. It has been used as a final clarifying step in water treatment since the19th century. It is becoming increasingly important in the tertiary treatment step of wastewater to produce effluent of superior quality for the purpose of reuse. Filtration is particularly applied when high flow rates of water with relatively low contents of suspended solids have to be treated. In a conventional water or wastewater treatment system, the filters are usually placed after sedimentation units to remove suspended particles, which escape without settling in the sedimentation units. When chemically pretreated and flocculated water is applied to a filter without a prior-solid liquid separation it is called direct filtration.

Mathematical modelling of downflow floating medium filter (DFF) with in-line flocculation arrangement

A laboratory-scale set-up consisting of rapid mixing device and floating medium filter was used to study the use of a downflow floating medium filter (DFF) with an in-line flocculation arrangement as a static flocculator and a prefilter. The semi-empirical mathematical model formulated incorporates flocculation within the filter, particle/floc attachment onto the filter and the detachment of flocs from the medium. The mathematical model for filtration takes into account the expansion of the filter bed. The removal efficiency of DFF and headless development were successfully simulated for different conditions of filtration velocity, filter depth and influent suspended solids (SS). The values of attachment coefficient a(p)β and headless coefficient β1 were found to be independent of filtration velocity, filter depth and influent SS concentration.

Surface coverage of filter medium in deep bed filtration : mathematical modelling and experiments

This paper highlights the importance of surface coverage in modeling the removal of particles in deep bed filtration. A model that considers the saturation of sites on which particle deposition occurs is used. Experimental results obtained with monodispersed suspensions of 0.46 and 0.816 μm latex particles at different influent concentrations and ionic strengths were used to calculate the fraction of filter grain surface (β1) on which actual particle deposition occurs. This will be useful in evaluating the filter performance in terms of the utilization of available surface area of the filter medium. Further, the level of dendrite formation of particles on filter grains during filtration is expressed in terms of β1 and the specific surface coverage, θT (the fraction of a filter grain surface that is covered by particles at time T, assuming that the filter grain is covered by a monolayer of particles). This can be used to compare the contribution of deposited particles in the removal efficiency of deep bed filtration for suspensions with different physical and chemical characteristics.

High rate filtration using buoyant medium : experiments and mathematical models

In this study, the high rate filtration system using buoyant medium of polypropylene or polystyrene was introduced with the study on its performance evaluation via: (i) specific surface coverage, (ii) ultimate specific deposit, (iii) blocking effect and (iv) particle detachment. The filter system was arranged in the downflow mode with an in-line flocculation. Experimental results obtained were analyzed using filtration models. This study showed that: (i) the specific surface coverage increased with the increase in the velocity; (ii) the ultimate specific deposit changed slightly at different filtration velocities and different flocculants; (iii) the blocking effect was significant in the transient stage removal of flocs; and (iv) the detachment model parameter was found to decrease with the increase in the adhesive force, Fad that acts on the flocs (above-micron size).

Explaining the levels of innovation and R&D in New Zealand's small and medium-sized enterprises : too many small firms?

This paper is concerned with explaining the levels of innovative activity in New Zealand's SMEs. It is arguable that New Zealand provides a special case where innovation and R&D levels are comparatively low in SMEs, yet, paradoxically, it is also a nation of high rates of entrepreneurial activity. This paper seeks to examine the factors that affect innovation levels in New Zealand SMEs from an analysis of panel data set of 1500 SMEs. We test research propositions based on existing theory and literature on innovation levels in SMEs and discuss our findings. Firm size is found to be significant; we argue that New Zealand has too few growth firms rather than too many small firms and we suggest that barriers to innovation, such as access to finance, remain an issue which should be a focus for government support.

Institutional analysis of strategic choice of micro, small, and medium enterprises : development of a conceptual framework

This paper presents a conceptual framework showing formal and informal institutions and their relationship with the strategic choice of micro, small, and medium enterprises (MSMEs) in a developing country setting. It emphasises how institutions at sub-national level (such as a region or city) influence the strategic orientations of MSMEs as many developing countries in Asia are undergoing decentralisation whereby sub-national government authorities are given more political, economic, fiscal, and administrative powers. Furthermore, it sheds more insights on the environmental (institutional) determinism-organisational (strategic) choice nexus. It offers propositions, questions as well as issues worth pursuing in empirical investigations in the future.

Social capital for knowledge management : the case of small and medium-sized enterprises in the Asia-Pacific Region

This article proposes a conceptual framework that explains that the social capital of a community shapes the innovation performance of small and medium-sized enterprises (SMEs) through knowledge management within the firm. The study's significance stems from the unprecedented effort in explaining how community social capital matters in the innovation performance of SMEs, a departure from previous studies that have typically examined market-related or hierarchical social capital in the form of formal networks and directly linked them to a firm's innovation performance without due regard for knowledge management within the firm as an antecedent of organisational innovation performance. The aim is to stimulate further thinking and empirical research on the subject of social capital of a community in the SME and/or entrepreneurial context.

The impact of test medium on use of visual analogue scales

Objectives: Visual analog scales are frequently used as a means of allowing participants to rate symptoms during clinical trials. The accuracy and reproducibility of these scales play an important role in determining the experimental value of the data they provide. This study was initiated to compare the data collected using paper- and computer-based (Tablet PC) analog scales to better understand the variability in data provided by a visual analog scale.

Methods: Thirty participants rated ocular comfort, redness, and clarity of vision (right and left eyes) on a nondemarcated horizontal line on both paper and a Tablet PC. Measurements were taken in the morning between the hours of 8:30 and 10:30 am and again the same day between 2:30 and 4:30 pm.

Results: The mean difference between the measures recorded in the morning for the 2 media was 2.6 ± 0.9 (confidence intervals, 2 standard errors of the differences) units on a 100 unit scale, with the Tablet PC having the higher mean measure. The limits of agreement (2 standard deviations of the differences) was 9.4 units. Comparing the difference of the differences (1.0 ± 1.3) between the 2 methods of measure (morning vs. afternoon) the visual analog scales on the Tablet PC seemed to have good reproducibility of agreement in comparison with the paper version.

Conclusions: Discrepancy analysis yielded no significant difference and slight bias between paper- and computer-based analog scales. Repeatability of measures using the Tablet PC was also demonstrated. These results suggest that the choice of medium does not significantly influence the outcome for subjective analog scales.

Enzymatic synthesis of isopropyl acetate catalysed by immobilized bacillus cereus lipase in organic medium

Selective production of fragrance fatty acid ester from isopropanol and acetic acid has been achieved using silica-immobilizedlipase of Bacillus cereus MTCC 8372. A purified thermoalkalophilic extracellular lipase was immobilized by adsorption onto the silica. The effects of various parameters like molar ratio of substrates (isopropanol and acetic acid; 25 to 100 mM), concentration ofbiocatalyst (25–125 mg/mL), reaction time, reaction temperature, organic solvents,molecular sieves, and initial water activity werestudied for optimal ester synthesis. Under optimized conditions, 66.0mM of isopropyl acetate was produced when isopropanol and acetic acid were used at 100mM: 75mM in 9h at 55◦C in n-heptane under continuous shaking (160 rpm) using bound lipase(25mg). Addition of molecular sieves (3 °A ×1.5mm) resulted in a marked increase in ester synthesis (73.0mM). Ester synthesiswas enhanced by water activity associated with pre-equilibrated saturated salt solution of LiCl. The immobilized lipase retained more than 50% of its activity after the 6th cycle of reuse.

The relevance and irrelevance of the brand for small and medium wine enterprises

Given the proliferation of wine brands, developing a brand without understanding its impact on wine choice is a risky business; particularly for SMEs with limited financial resources.

This paper fills an important gap in the wine marketing literature, particularly as it relates to SMEs in the sector, by investigating the effect of the brand on wine choice. Surveying a range of wine consumers, it was found that while the brand was relevant in wine choice the weighted importance of the brand elements changed across consumption situations. This novel finding should assist SMEs to grow their businesses beyond the traditional cellar door.

What drives the adoption of electronic markets in Australian small-and-medium sized enterprises? – an empirical study

This paper reports a study of the critical determinants for adopting electronic markets (e-Market) in Australian small-and-medium sized enterprises (SMEs) within the technology-organization-environment (TOE) framework. Structural equation modelling and logistic regression are used for identifying the critical determinants for the adoption of e-Markets by Australian SMEs through testing a proposed conceptual model and proposing an alternative model. This study contributes to existing research by enriching an understanding of the critical determinants of adopting an e-Market in Australian SMEs and by providing a validated model for the interrelationships of the determinants in technology adoption.