Authors

Holly Johnson Churman, Technology Manager

Lisa Henthorne, Senior Vice President and Chief Technology Officer, Water Standard, USA

Introduction

Harmful algal blooms (HABs), though challenging to predict, are anticipated to increase in quantity and distribution, challenging effective operation of coastal desalination facilities today and in the future. The purpose of this paper is to provide an overview of HABs, including their basic characteristics, factors that influence their generation, and key risks to desalination facilities. Five areas of plant design, including detection and monitoring systems, intakes, screens, dissolved air flotation, and membrane filtration equipment, will be discussed in terms of their strengths and shortcomings to address HABs.

Abstract

HABs are the result of anthropogenic or environmentally-driven eutrophication events that pose risk to human health, natural resources and coastal facilities. HABs are projected to grow in frequency and distribution in coming years. In parallel with this trend, more thermal and membrane desalination facilities will be constructed globally. As a result, many coastal facilities will be susceptible to HAB risks. Understanding the nature of HABs, their challenges, and ways in which they can be monitored and mitigated are the first steps needed to effectively address HAB risks.

The purpose of this paper is to present an overview of HABs, including their typical characteristics, discuss factors that lead to their development, and identify specific aspects of HABs that pose the greatest risks to thermal and membrane desalination facilities. Five areas of desalination facility and operations design capable of addressing these risks, including detection and monitoring technologies, intakes, screens, dissolved air flotation, and membrane filtration equipment, will be discussed in terms of their strengths and shortcomings to address HABs. While these technologies offer compelling advantages to manage the change in water quality that accompanies HABs, engineers and operators must fully consider technical, economic, and other tradeoffs in order to properly plan and manage events when they occur. As these technologies continue to improve, engineers and operators will have the ability to respond to HAB events and design new desalination facilities more efficiently in the future.

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Please click on manuscript name Treating A Moving Target: Harmful Algal Blooms

Authors

Stephen P. Chesters

Matthew W. Armstrong

Introduction

Reverse Osmosis membrane cleaning is essential for efficient plant operation and yet there has been very little innovation or development in over 30 years. This paper reviews best practice on reverse osmosis (RO) membrane cleaning. It challenges preconceptions and describes novel approaches for the removal of foulants and scale deposits from membrane surfaces.

Abstract

Over the last ten years there have been significant developments in new devices for energy recovery, new membrane materials, and new sizes and orientations of reverse osmosis (RO) plants, all designed to reduce costs and improve efficiency. The fundamental issue of keeping membrane surfaces clean to ensure efficient RO plant operation has seen relatively few new ideas. This is surprising as any fouling of the membrane surface will have a dramatic effect on energy consumption and plant efficiency.
This paper demystifies RO membrane cleaning which is often described by practitioners as an art as much as a science. The more science that is applied the better results will be. Current best practice is reviewed and practical suggestions are given to improve results.

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Please click on manuscript name 140824 Chesters – IDRA White Paper – RO Membrane Cleaning

Authors

Peter G. Nicoll

Abstract

Forward Osmosis (FO) over the past five years has generally attracted more attention, both academically and commercially, with a number of companies raising finance on the back of its potential. The process exploits the natural process of osmosis, which is how plants and trees take up water from the soil – a low energy, natural process. It works by having two solutions with different concentrations (or more correctly different osmotic pressures) separated by a selectively permeable membrane, in the case of the plants and trees their cell walls, and ‘pure’ water flows from less concentrated solution across the membrane to dilute the more concentrated solution, leaving the salts behind. The clue in the potential applications is that it is widely used in nature, however it is only relatively recently that its full potential has begun to be recognised industrially. It can be used on its own or in combinations with other processes, for example desalination, concentration and renewable power generation.

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Please click on manuscript name 140824 Nicoll – IDRA White Paper – Forward Osmosis-A Brief Introduction