SIPS 2018

DETAILLED PROGRAM OVERVIEW

Environmental and Energy Issues in Water Treatment Processes
Raphael Semiat¹;
¹TECHNION IIT, Haifa, Israel;
PAPER: 10/AdvancedMaterials/Keynote (Oral)
SCHEDULED: 11:20/Tue./Guaratiba (60/2nd)

ABSTRACT:
The growth in population and in the standard of living in developing countries, coupled with inefficient use of water and pollution of available water resources, have driven desalination to be a major source of fresh water for both domestic and industrial purposes. The challenges in water management are among the most important problems facing the world today. The shortage of clean water is at the heart of critical health issues in developing countries, and is the focus of ecological and safety concerns even for the highly developed nations. To provide water for drinking and agriculture, we must desalinate and clean natural water sources, reclaim polluted water, purify water with different degrees of contaminants, and improve the effectiveness of water handling (storage and delivery) systems ranging from large desalination plants to waste water treatment facilities and down to family's water purification systems. We must remove contaminants that include inorganics (metals and ions), organics (e.g. toxic waste, pharmaceuticals) and microorganisms (bacteria, viruses, etc.). At the heart of these diverse problems stands the need for new ways to clean water, to safely dispose of the extracted waste, to properly reuse the cleaning systems and to keep the environment clean. The cost of desalinated water is higher than the cost of natural water if available in the vicinity but can be lower if natural water is brought from long distance. The popular concept is that desalination consumes high energy; however, like in the process industry, the cost is based on optimization of all parameters involved, not only the energy. It is not only the cost of the process components, but also most importantly, the environmental parameters that need to be properly considered. The potential environmental impacts of desalination are related to the energy generation process as well as to the design and management of the desalination process. The importance of these impacts depends on the type of technology used. Energy consumption of desalination processes is very low in comparison with the total national energy consumption for electricity and transportation. It was shown that the energy consumption of most desalination processes constitute only a small fraction of the total national energy consumption. For example, the energy requirement to produce an annual desalinated water capacity of 600 million m3/y in Israel is less than 1.3% of the Israeli national energy consumption. It should be noted that it is easier to save 1.3% of the national energy consumption than about 80% of the urban water consumption. Energy consumption depends on the location of the plant and the distance of the plant from the seawater suction point, and the energy cost is highly dependent on the type of energy source. Other environmental issues may also affect the water cost, and it is important to keep the environment intact while keeping desalinated costs to the possible minimum. In literature and in real life there are considerable concerns regarding the environmental impacts of desalination technologies. The main concerns are related to emission of air pollutants and greenhouse gases, entrapment of marine life on the intake side, and discharge of relatively high-temperature, salinity-elevated and chemical-laden concentrate. Nevertheless, limited research is available on these possible ecological and biological impacts, particularly on the long term effects on the marine environment. Existing data revealed that only a small area, adjacent to the concentrate disposal point, is affected by elevated salinity and temperature after which complete dilution with the seawater diminishes any further affects. Israel made significant steps to provide affordable solutions based on a wide distribution system, desalination (80% of the urban water consumption), tertiary treatment of wastewater for irrigation, drip irrigation for reduction of water consumption, and improved agriculture techniques. However, there is always room for improvements. It is essential to improve desalination steps in order to reduce the cost. New directions may include improved membranes—especially UF membranes, improved pretreatment processes, and increased recoveries as applied effectively near zero liquid discharge in inland brackish water desalination. It is essential to improve wastewater treatment by better techniques like MBR and better treatment for removal of tracers of organic and inorganic contaminants. An important subject is the treatment of produced water from the gas and oil industry, treatment of polluted aquifers, development of small water treatment and recovery for remote communities, and more. Priority should be given in the near future to development of renewable energy sources and water supplies that meet sustainability and environmental requirements. This presentation summarizes the environmental impacts of most aspects of desalination processes, highlighting the recognized problems and their available industrial solutions. The aspects related to techniques, energy and environmental issues investigated in our water research program would also be discussed.