Submerged Biotower Technology for Tertiary Nitrification of Poultry Abattoir Wastewater

The paper describes the design and operation of a submerged biotower, i.e. flooded upflow reactor which utilises a random-packed polypropylene medium for supporting the biomass. The process can be used for carbonaceous removal or nitrification. In the application which is described, the process has been used for tertiary nitrification of a poultry abattoir wastewater as an extension to the existing effluent-treatment plant. Details of process commissioning at low temperatures are given and results from twelve months'operation are discussed. Operating costs are compared with other processes.     

The Prevention of Oil and Chemical Pollution: Proactive Approaches in the UK and Canada

In the UK, various initiatives have been launched in an attempt to provide guidance on the occurrence and avoidance of oil and chemical pollution. Despite these efforts, oil and chemicals remain a major cause of pollution. In Canada, similar initiatives have been more successful due to a participative approach to campaign development and implementation. This paper compares UK and Canadian initiatives and identifies factors which led to the success of the Canadian campaigns.     

Strategies to Combine the Functions of Ecology and Navigation in the Scheldt Estuary

During recent years, water management in The Netherlands has been broadening its scope by: (a) including aspects of economics, sociology and physical planning, and (b) introducing interactive policy making; this paper illustrates these developments using the Westerschelde estuary as an example. The Westerschelde strategy aims at optimizing the multi-national use of this estuary. The main functions are navigation and ecology, and the paper shows how these functions can be combined. An interactive management model, the 'COSMO-Westerschelde'is described, which assists decision makers in comparing strategies for estuarine management under different scenarios.     

The Effect of Ozonation on Particle Removal in Drinking-Water Treatment

The effect of the introduction of additional process stages in a surface-water treatment plant was studied in order to investigate how particle removal could be optimized. Particle counting is considered to be a useful indicator of treatment performance. This paper is based on results which were obtained from trials on a water-treatment plant treating surface water; these consisted of a combination of modifications to existing full-scale plant and a specially constructed pilot plant.     

Faecal-Indicator Budgets for Recreational Coastal Waters: A Catchment Approach

This paper explores the application of a catchment faecal-indicator budget approach to the examination of faecal-indicator sources impacting on coastal recreational water quality. This involves (i) the characterization of water quality in sewage effluent and riverine inputs, and (ii) measurement and estimation of input flows; the product of these components yields the input flux of indicator organisms from each source. The impact of sewage-treatment scenarios on budgets is also investigated.     

Treatment and Disposal Scheme for the Sewage of Athens

The sewage from the Greater Athens area is discharged without treatment to the nearby Saronicos Gulf. Recently the Greek government decided to implement an appropriate treatment and disposal scheme, on the basis of a study of the hydrodynamic behaviour of the Gulf and the fate of the discharged pollutants. The study was conducted with the aid of suitable hydrodynamic and water quality models for a number of alternative treatment schemes, ranging from primary treatment to biological treatment with seasonal nitrogen removal, combined with outfalls of different lengths. The results indicate that, although none of the examined schemes will lead to an immediate substantial impact, the scheme that includes biological treatment with seasonal nitrogen removal can eliminate the danger of serious ecological disturbances at a reasonable cost.     

Post-Construction Effects of the Cameroonian Lagdo Dam on the River Benue

This paper examines the immediate and long-term effects of the Lagdo dam on the Upper Benue river basin in Nigeria. From routine monitoring of the River Benue, it was found that some immediate deleterious effects were (a) siltation of the river bed and channel, (b) frequent flooding events, and (c) reduction in flow. Consequently, these factors have constrained irrigation, navigation and fishing activities which were formerly undertaken along the river. Similarly, water-supply intake structures and irrigation abstraction facilities along the river have either been silted up or threatened. Allowing for assumptions on a real-time operational schedule of the dam, coupled with future water demands in north Cameroon, longterm effects of the dam on the Benue basin within Nigeria are predicted.     

Experimental‐numerical research on the seismic performance of URM buildings made of lightweight AAC blocks / Experimentell‐numerische Untersuchung zum seismischen Verhalten von unbewehrten Mauerwerksgebäuden aus Porenbetonblöcken

Masonry walls constructed with lightweight AAC blocks and thin‐layer mortar meet the increasingly strict requirements of energy efficiency and sustainability. In this sense, they represent an excellent solution for modern buildings, not only for external cladding but also as loadbearing elements. Despite the possible advantages of using lightweight AAC masonry, a specific assessment of its seismic performance is mandatory in order to set design recommendations allowing to reach safety levels consistent with those required for other masonry types complying with EN 1998 standard requirements. A comprehensive study on the seismic performance of unreinforced masonry buildings made of lightweight AAC was carried out in an integrated experimental‐numerical approach. The experimental campaign provided the necessary information to setup a reliable numerical model to be extensively used to assess the seismic performance of a number of prototype AAC masonry buildings with different characteristics, by means of both linear and nonlinear static (pushover) analysis. The results of this systematic numerical assessment were eventually used to draft design recommendations, to set parameters (behaviour factors) to be used in linear analysis and to calibrate rules for simple buildings.     

Redistribution of internal forces in the lateral bracing system / Schnittgrößenumlagerungen bei der Gebäudeaussteifung

The lateral bracing system of a building should ensure the stability of the building, in terms of the usability and the total load capacity. The governing loads for the lateral bracing system are horizontal loads due to wind and earthquake. The horizontal loads are traditionally distributed to the bracing elements according to the uncracked elastic state dependent on the bending stiffness in the elastic (uncracked) state. This method does not allow consideration of non‐linear effects and load redistribution. Within the framework of the PRB Research Cooperation – Improving the Practical Use of Structural Design Standards through pre‐normative work – Subcontract 5: Masonry Construction, Subproject 3: “Large Shear Walls” [7], the cracked or plastic state can be taken into account through a displacement based approach. A matrix formulation for both the linear and cracked states has been derived and implemented.     

Surface-Water Abstraction Controls in Scotland

ABSTRACT The system of abstraction controls for irrigation in Scotland is one of local control orders where, to limit abstractions from any particular watercourse, the river purification authority must apply for an order from the Secretary of State for Scotland to cover abstractions from that one watercourse and its catchment. This contrasts sharply with the heavily protective system in England and Wales where the National Rivers Authority has statutory powers to license all abstractions. The purpose of this paper is to examine the abstraction control system in Scotland with a view to highlighting its advantages and limitations, and to suggest ways by which the system can be improved or made more effective.