by Peter Gleick, President
October 13, 2014
As input to the ongoing discussions about how to meet and overcome the spreading risks of Ebola, here are some summary thoughts about the water-related components of U.S. efforts. Specifics about the operations and effectiveness of water treatment or supply technologies, or the medical and health implications of their use must be verified by the designers/makers of the technology along with medical experts from the US Centers for Disease Control (CDC), World Health Organization (WHO), West African health and water officials, and related institutions.
1. Water Supply Needs and Usage
Any medical facility, hospital, field station, isolation unit must have a supply of fresh water that is adequate in flow volume and quality. This requirement, and the need to develop such a reliable supply in advance of facility construction or placement, is as or more vital than the need for reliable electricity, although as noted below, these two resource needs are also related and connected.
Volume of Water Needed
Few studies have assessed average water use by hospitals; fewer have done this assessment for emergency field isolation units or rural medical units. Larger hospitals are reported to use between 40 to 350 gallons per patient per day (150 to 1300 liters per person per day), but only about 60% of this is used for medical procedures and sanitary purposes. Another source identifies typical urban hospital hot water demand at around 35 gallons per person per day (160 liters per person per day).
While these data suggest that emergency minimum water supply volumes on the order of 150 to 200 liters per person per day might be sufficient, it should be a top priority to inquire of current medical facilities in Liberia, Guinea, and other affected areas of West Africa for specific data and insights on their current level of water use as well as the end uses of that water (washing, sanitation, sterilization of equipment, cooking, etc.).
Water sources can include rainwater, surface water from rivers, surface water from lakes and ponds, groundwater/aquifers, remote delivery via tanker, pipeline, or municipal system. The availability of these options is highly locally specific, and no general recommendation can be made without knowledge of the site to be chosen for a treatment facility. It is thus vital that early and fast assessments be conducted of available water sources (including both quantity and quality). Given the high variability of the hydrology and climate in West Africa, a reliable source of safe, clean groundwater may prove to be the best option, but will require a geophysical assessment and an experienced water well drilling team, together with sufficient engineering expertise to install the necessary pumping and treatment infrastructure.
It is essential that the quality of at least part of the water supply be potable, as defined by World Health Organization, European Commission, or U.S. Environmental Protection Administration standards. (Any one of these standards would be sufficient.) Water protected to a “potable” standard will greatly reduce the risk of additional water-related diseases, which would vastly worsen the health outcome of both working staff and patients. This will require either a guaranteed source of water that is safe, or an on-site treatment system that can purify water of any available source to a specified, desired quality. An on-site system is preferable because of the greater certainty (compared to depending on natural purity of a potentially unreliable or variable source), but it has higher operational complexity and costs.
A key point: water use in an emergency field hospital can be split into both potable/high quality and non-potable needs. If non-potable water is available, and there are substantial water-use requirements that do NOT require potable water, the system required to produce potable water can be smaller, less energy intensive, and less costly. In such a “dual-system” case, however, care must be taken to ensure that potable and non-potable needs and supplies are kept separate and isolated to prevent cross-contamination risks.
Energy-Water Nexus Issues
Both reliable energy and water are vitally important resources for any emergency medical facility. As part of the need to supply water, however, there are also significant energy needs for:
- Water-supply delivery (via pumping of groundwater, pipeline operation, or tanker delivery)
- Water treatment is often energy-intensive, depending on the methods used (boiling, membrane operation, ozone or ultraviolet disinfection, etc.)
The Table below shows the energy requirements for various water-treatment technologies. In planning the total energy system needs for any facility, these water-related energy demands must be taken into account, along with the backup water storage needed to provide treated water in the event of energy outages.
Along with water-supply reliability, sufficient on-site water storage must be provided with two important characteristics:
- Sufficient volume to cover fluctuating demand and the risk of water-supply outages caused by changes in the supply or by loss of electrical power to provide treated water.
- Sufficient quality protections to ensure that water in storage remains safe for the specified uses.
There are a wide variety of commercially available or military-grade storage tanks, plastic “bladders,” or other kinds of water bags or containers and the calculation of sufficient backup volume is easy to make if information is available on the level of demand. A system must also be put in place to test the water quality of stored water on a regular basis.
2. Water that may be contaminated with Ebola virus
A separate water-quality risk is that during patient care and treatment, contaminated fluids, including water, will have to be reliable handled, treated, and neutralized. According to the World Health Organization, Public Health Agency of Canada, and the US CDC, Ebola virus is known to be susceptible to solutions of chlorine bleach, germicidal chemicals, gamma radiation, sufficient ultraviolet C light exposure, some soaps, alcohol-based sanitizer (at least 60% concentration), and by boiling water., , (See Box 1: Ebola Susceptibility to Disinfectants and Physical Inactivation, for some specific data.]
Box 1. Ebola Susceptibility to Disinfectants and Physical Inactivation
From the Public Health Agency of Canada. http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/ebola-eng.php
SUSCEPTIBILITY TO DISINFECTANTS: Ebolavirus is susceptible to 3% acetic acid, 1% glutaraldehyde, alcohol-based products, and dilutions (1:10-1:100 for ≥10 minutes) of 5.25% household bleach (sodium hypochlorite), and calcium hypochlorite (bleach powder). The WHO recommendations for cleaning up spills of blood or body fluids suggest flooding the area with a 1:10 dilutions of 5.25% household bleach for 10 minutes for surfaces that can tolerate stronger bleach solutions (e.g., cement, metal). For surfaces that may corrode or discolour, they recommend careful cleaning to remove visible stains followed by contact with a 1:100 dilution of 5.25% household bleach for more than 10 minutes.
PHYSICAL INACTIVATION: Ebola are moderately thermolabile [can be destroyed or deactivated by heat] and can be inactivated by heating for 30 minutes to 60 minutes at 60°C, boiling for 5 minutes, or gamma irradiation (1.2 x106 rads to 1.27 x106 rads) combined with 1% glutaraldehyde. Ebolavirus has also been determined to be moderately sensitive to UVC radiation.
Source: Public Health Agency of Canada. http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/ebola-eng.php. Accessed October 5, 2014.
A wide range of water-treatment systems can ensure that water supply is safe, including chlorine-based treatments, ultraviolet light treatment, and top-quality reverse osmosis membrane systems. The CDC provides a short overview of various treatment options and their ability to remove viruses here. Before choosing a water-treatment system, however, manufacturers must confirm that they are designed and can be operated to specifically remove or inactivate Ebola-type viruses with high reliability.
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