The water supply system provides us with clean water. It is based on large-scale infrastructure including the water purification facilities and the water supply and its piping installation equipment, and there are various measures taken to maintain its safety. The Water Analysis Center, Environmental R&D Promotion Department of Maezawa Industries, Inc. utilizes Nikon's microscopes to inspect whether Cryptosporidium, a pathogenic protozoan, exists in raw water intended for tap water* or the tap water itself.
- *Raw water refers to the original water before treatment including the surface water of rivers, etc., or underground water.
Clean water supports our lives
From our everyday lives to agriculture as well as industry, water always fundamentally supports humanity's existence. In particular, drinking water is essential for maintaining our lives. According to a UNICEF*1 survey*2, as of 2017, approximately 71% of people were able to access drinking water that was safely managed. UNICEF defines "safely managed drinking water" as "drinking water that people can access in their homes whenever it is necessary and is obtained from a water source that is not contaminated by excrement or chemical substances," which mostly corresponds to tap water. We can always obtain access to clean and safe water through the faucets close to us thanks to the facilities of water intake, purification, and distribution, and widespread piping systems extending like a net.
According to a survey conducted by the Japanese Ministry of Health, Labor and Welfare in 2017, the water supply coverage ratio in Japan was 98%*3. Recently, introducing an advanced water purification system that can eliminate almost all of the small amounts of chemical substances, odors, and organic substances found in water supplies, is being promoted. Safely managed clean drinking water is now supplied to more people than ever before.
We interviewed Kiyomi Baba, General Manager, Water Analysis Center, Environmental R&D Promotion Department, Environmental Business Headquarters, Maezawa Industries, Inc., who conducts various water analyses. She is an experienced specialist who possesses extensive knowledge and advanced skills in the evaluation of Cryptosporidium, a pathogenic protozoan that can sometimes be found living in raw water intended for tap water or the tap water itself.
- *1UNICEF (United Nations Children's Fund) was established in 1946 in order to provide emergency support for children suffering after World War II. UNICEF currently works in over 190 countries and regions to protect the rights of every child in the world.
- *2Source: WHO/UNICEF JMP (2019) Progress on household tap water, sanitation and hygiene 2000-2017. Special focus on inequalities.
- *3The population ratio of municipal water supply (supply for population: 5,001 and over) + small scale public water supply usage (supply for population: 101 to 5,000) + private water supply systems (Supply of water for private use with supply for population of 101 or more, or with the maximum daily water supply volume of more than 20 m3.) to the total population.
Water quality inspection for maintaining the safety of drinking water
Maezawa Industries, Inc. (hereinafter "Maezawa Industries") is a comprehensive water infrastructure manufacturer that covers water and sewage facilities and other various water treatment equipment. Its manufacturing base is located at the Saitama Plant in Satte City, Saitama Prefecture, which houses the analysis center where Ms. Baba works as a General Manager. The center conducts analyses of water and sewage when proposing designing, developing, manufacturing, and building water treatments and wastewater treatment equipment. In addition, it analyzes tap water as an inspection facility registered by the Waterworks Bureaus and health centers stipulated in Article 20 of the Waterworks Act.
Article 20 of the Waterworks Act relates to inspections that protect the safety of drinking water in the Water Supply Law governed by the Ministry of Health, Labor and Welfare for the water supply business. Strict inspections are required to be performed on both a regular and provisional basis, covering 51 items such as colors, odors, bacteria, pH values, heavy metals, organic chemicals, and other contaminants. These inspections were previously handled by waterworks bureaus and health centers within local governments. However, in 2003, they were allowed to outsource to private corporations. Maezawa Industries is one of the 200 facilities in Japan to have been registered by the Ministry of Health, Labor and Welfare. Moreover, Ms. Baba is authorized by the Association of Examination and Inspection for Supplied Water*1 as an instructor to provide guidance of inspection techniques.
Formerly, the Water Analysis Center of Maezawa Industries had inspected the 51 items. However, the center now has a system that specializes in inspecting for the protozoan called Cryptosporidium. Although it is not included in the 51 items mentioned above, it is regarded as an essential inspection. Since this test requires highly complicated procedures and high levels of skills - making it difficult for other companies to conduct, the center handles inspections of the raw water intended for tap water and the tap water itself at the request of local governments around Japan.
Cryptosporidium is a parasitic protozoan that infects mainly humans and other mammals, such as cattle and pigs, and enters its hosts orally from drinking water. After infection, it multiplies in the small intestine, and elsewhere, and causes infectious diseases. If it develops within the human body, it may cause symptoms such as abdominal pain, diarrhea, nausea, fever, and headache. For people with weak immune systems, the symptoms may become severe and even lead to death. If a water source becomes contaminated with Cryptosporidium, there is a risk that the infection will spread via tap water unless removed at water purification facilities. This has actually happened in the past. In 1993, over 400,000 people were infected in Milwaukee, U.S.A., and about 9,000 people were reported as infected in Saitama Prefecture, Japan in 1996, as well.
Infectious cycle of Cryptosporidium
- *1The Association of Examination and Inspection for Supplied Water mainly focuses on training special inspectors with accurate judgement who deeply understand inspection techniques utilized for water quality, water quality management, etc. and manages accuracy to maintain the inspection quality. In terms of Cryptosporidium, the association contributes to improving reliability inspection organizations with membership by instructing inspection methods and providing second opinions.
Cryptosporidium inspection can only be enabled with dedicated microscopy
Cryptosporidium lives in water, being covered by a thick shell called an "oocyst". Because of this shell, Cryptosporidium is highly resistant and cannot be removed even with the application of chlorine used for disinfecting water purification plants. In addition, it has strong infectivity even with a small amount*1, which means that even if just a single individual organism escapes inspection it could be a serious problem. This thick shell and strong infectivity make inspections for Cryptosporidium extremely difficult.
Regarding raw water intended for tap water and treated water, which are what the Water Analysis Center mainly inspects, 10 to 20 liters of water are normally strained through filter paper gradually as sample water. Next, several highly complicated and time-consuming processes take place including the separation of particles, such as the oocysts, from the filter paper along with selection and purification. Through these processes, the well water source is concentrated down to a few milliliters. Using this, a preparation is made which is then observed employing a microscope.
Cryptosporidium can only be observed through fluorescence microscopy that employs a differential interference device*2. First, targets stained a blue-green color are observed with fluorescence imaging, to confirm the presence of oocysts. Rounded objects radiating in blue-green may be found, which might be Cryptosporidium, but this cannot be conclusively decided. At this time, they can be only observed from the outside, and algae could possibly be radiating. So, a differential interference microscope is used to observe the inside structure. Differential interference microscope observation enables the capture of transparent subjects via the contrast of light intensity. In order to capture a clear image, this test requires subtle, skilled techniques in adjusting the position of a condenser lens and the contrast of light. "This very subtle adjustment is the biggest reason why the Cryptosporidium inspection is said to be so difficult", explains Ms. Baba. Once a structure resembling four banana-like objects stuck together is detected inside the thick shell using differential interference observation, a positive identification of Cryptosporidium can finally be made.
It takes from one to several days to complete the entire process of the Cryptosporidium inspection, depending on a worker's skill level and the amount of water to inspect. It is a highly complicated and painstaking task. Ms. Baba has been conducting this inspection for about 20 years, and continuously strives to share/instruct the techniques of the Cryptosporidium test method using microscopes. After using fluorescence microscopy with differential interference devices for so many years, Ms. Baba admits the device now seems like a part of her own body.
"If you fail to separate or purify even a single Cryptosporidium organism or you miss it during microscopic observation, the inspection result will be negative and may result in providing people with dangerous drinking water. I would like to continue to develop my inspection skills further so that I can precisely detect even miniscule amounts of Cryptosporidium. Also, I would like to share what I have learned with more inspection technicians than ever before", she said.
Thanks to water quality inspection testing, a great number of people can safely drink tap water. Nikon's microscopes are playing an active role at the site.
- *1Cryptosporidium is highly infectious. According to a human infection experiment conducted in the United States, it is estimated that half of the subjects would be infected if they orally ingested about 130 Cryptosporidium organisms. Another experiment shows that toxic intensity depends on its strains and less than 10 Cryptosporidium have the potential to cause infection.
- *2A microscope that can perform fluorescence observation and differential interference observation with one unit. During fluorescence observation, it utilizes a light source that can excite (irradiate) a fluorescent specimen. During differential interference observation, it utilizes a normal light source and permits observation by changing the difference in the refractive index when light passes through an unstained observation target and the optical path difference (difference in the way light passes), due to the variation of the surface shape into bright and dark contrast.