Bio-layer management in anaerobic membrane bioreactors for wastewater treatment.

Membrane separation technology represents an alternative way to achieve biomass retention in anaerobic bioreactors for wastewater treatment. Due to high biomass concentrations of anaerobic reactors, cake formation is likely to represent a major cause of flux decline. In the presented research, experiments are performed on the effect of biomass concentration and level of gas sparging on the hydraulic capacity of a submerged anaerobic membrane bioreactor. Both parameters significantly affected the hydraulic capacity, with biomass exerting the most pronounced effect. After 50 days of continuous operation the critical flux remained virtually unchanged, despite an increase in membrane resistance, suggesting that biomass characteristics and hydraulic conditions determine the bio-layer formation rather than the membrane's fouling level. The concept of bio-layer management is introduced to describe the programmed combination of actions performed in order to control the formation of biomass layer over membranes.     

Accounting for control and trust building in interfirm transactional relationships

This paper theorises the accounting-control-trust nexus in interfirm transactional relationships. In the context of such relationships, accounting has predominantly been conceptualised as a control technology. However, in our paper we analyse stable and durable relationships as being the results of interaction between control and trust building. Such an analysis calls for an additional conceptualisation of accounting as a trust building technology. Furthermore, we explain the interaction between accounting for control and accounting for trust building in the context of a process of embedded agency.     

METROPOLITAN HOUSE PRICES IN SOUTH AFRICA: DO THEY CONVERGE?

The question this paper investigates is whether or not different metropolitan areas each constitute a separate housing market or whether or not there is a single South African housing market. Theory on the Law of One Price suggests that if products or geographic areas belong in the same market, their absolute prices must converge, so that their relative prices are stationary. By using cross-sectional time series data of five metropolitan areas, the paper tests for the Law of One Price by applying the Im, Pesaran and Shin panel unit root test. The paper finds strong evidence of convergence in large middle-segment house prices and weaker support for convergence in medium middle-segment house prices. In addition, the paper finds no evidence for convergence in small middle-segment house prices. This suggests the existence of a national market for large and possibly middle-segment houses in metropolitan areas, but separate metropolitan markets for small middle-segment houses. In addition, the paper estimates the speed of convergence and finds that large middle-segment house prices converge within two to seven quarters, while the speed of convergence for medium middle-segment house prices in three of the five areas is five to eight quarters.     

Competition Policy: What are the Costs and Benefits of Measuring its Costs and Benefits?

Summary  Competition authorities are increasingly measuring the effects of their enforcement actions, seeking a robust justification for the proliferation of competition policy. We highlight the importance of identifying the right counterfactual against which to measure effects, and set out the relevant categories of costs and benefits. We then explore how a balance can be struck between the benefits and inherent limitations of these measurement exercises. Relatively crude analyses of cartel action benefits can be sufficient to achieve public legitimacy for competition policy. Assessing the effects of merger and conduct inquiries is often ambiguous, but could be used to improve decision-making processes. Director and Managing Consultant, respectively, at Oxera, Oxford and London. The valuable comments of Fod Barnes, Kerry Hughes and an anonymous referee are gratefully acknowledged. The opinions expressed in this article are those of the authors alone.     

Risk Sharing in a World with Processing Costs: Trading versus Banking

We analyze the bank versus exchange problem in a Diamond Dybvig (1983) economy with exogenous transaction processing costs. We find that processing costs in the market enables the bank to overcome the side trade threat ( Jacklin (1987) ) and offer some desirable liquidity insurance. Moreover, in the bank equilibrium processing costs are proportional to consumption, while in the market economy early and late consumers incur equal costs. These two effects explain that for a given level of aggregate processing costs, the bank economy is superior. On the other hand, the number of transactions in the bank economy is larger. It is for this reason that if processing costs are proportional to transaction value, and independent of the mechanism used, the exchange economy is superior.     

The impact of cleaner processing on nutrient availability in the bleached kraft industry.

The pulp and paper industry has invested heavily over recent years in cleaner processing, to reduce losses and minimise its impact on the environment. Over the past fifteen years, a New Zealand integrated bleached kraft mill has undergone a comprehensive programme of upgrades to increase production, reduce water consumption and streamline its biological treatment process. Whilst the overall discharge of contaminants from the site decreased, the treatment system performance did not show a concurrent improvement as may have been expected. Reduced BOD removal, low dissolved oxygen levels, and poor solids settlability were symptomatic of phosphorus limitation in the aerated lagoon treatment system. The wastewater entering the system was found to be phosphorus limited at a BOD:P ratio of 100:0.2. Mono-ammonium-phosphate was supplemented, at approximately 30 kg P/d, to raise the phosphorus levels to a BOD:P ratio of 100:0.3. Treatment efficiencies improved very quickly after phosphorus dosage, with a 50% reduction in BOD and TSS discharge, a significant increase in dissolved oxygen levels, and improved BOD removal (85% to 93%). This case study demonstrates that whilst more closed operation can result in reduced discharge of organic loads, there may be negative impacts on the availability of nutrients for balanced biological growth.     

Infrastructures and Societal Change. A View from the Large Technical Systems Field

Infrastructural and societal changes intertwine in multiple ways. This makes the societal implications of infrastructural projects difficult to assess and anticipate. Yet in present day network societies this task is particularly urgent. This paper first identifies two positions that tend to monopolize and deadlock debates. Next it examines two decades of research in the Large Technical System (LTS) research field for alternative approaches to this issue, before finally suggesting distinguishing between the four increasingly indirect moments of (co-) construction of infrastructures and societies. These may be related causally, but also add their own moments of contingency, agency, and choice.     

Standardization Process of Systems Technologies: Creating a Balance between Competition and Cooperation

Many firms are experimenting with how to standardize new technologies. They may use proprietary technologies for their products and services, and let them compete in the market selection. Alternatively, they can cooperate to jointly set a standard and experiment with combinations of market process and cooperation. If firms let the market decide, they can compete with technologies and need not invest time and effort in hammering out a standard. If they do incur the costs of negotiated standardization, they may enable end users to realize the benefits of standards. A hybrid standardization process combines the advantages of both market selection and negotiated decision making. This paper presents a contingency framework to identify conditions that will affect the preferred standardization process for vendors who introduce new technologies. A major contingency that this paper points to is the systemic nature of technologies in information and communication technology industries. The more systemic the technology is (in a way to be clarified), the less likely that firms will establish a hybrid standardization process. One advantage of decomposing technology systems in smaller components (modules) is that this approach enables firms to combine market selection with negotiated selection of standards.