Introduction
Ancient water distribution and treatment methods originated millennia before principles of modern hydraulic design, such as conservation of mass, energy, and momentum, were even put to thought [1]. Spending most of human history as hunters and gatherers, only in the last 10,000 years did civilizations develop more sophisticated means of agriculture-use and, in turn, water distribution methods [1]. Still, water technology development during antiquity, much before the contributions of Leonhard Euler (1707-1783), Blaise Pascal (1623-1662), Leonardo da Vinci (1452-1519), or even Archimedes (287-212 BC), was extremely sophisticated and sustained entire ancient civilizations [1]. Ancient civilizations of note for water technology advancements include: Mesopotamia, Greece, Indus Valley, and Egypt. Furthermore, the influence of ancient water engineering is seen in modern-day water disinfection, filtration and testing methods.
Ancient Civilizations
Mesopotamia
Being situated between twin rivers, Ancient Mesopotamia benefited greatly from the plentiful water supply and resulting lush flat lands [2]. The enhanced farming that resulted from the nourishment delivered to neighboring lowlands due to river floods earned the area its name; the Fertile Crescent [2]. Residing in the northern part of the Fertile Crescent (occupying present-day Iraq, and parts of Iran, Turkey, Syria, and Kuwait [2]), Mesopotamians developed irrigation-based agriculture in their southern alluvial plains (where wells could be easily dug), while dry-farming progressed in the north [1]. The civilization developed a complex system of canals to be used both for irrigation and as waterways. In addition to water technology, Ancient Mesopotamia also pioneered water sanitation in the form of wastewater and stormwater drainage systems [1].
Greece
Ancient Greek water technology evolution is traced mostly to the Hellenistic period, which saw the installation of lavatories in private houses, public buildings and sanctuaries [1]. Often an indicator of better living standards and economic prosperity, household lavatories were strategically placed on the street-adjacent side of buildings for sewage to be drained through ditches along the street [13]. Lavatories were equipped with a peripheral ditch, through which water was either supplied by natural flow or manually with a container, in order to facilitate sewage disposal. Examples of Greek well shaped public and private lavatories are scattered throughout archeological finds dated back to mid-4th century BCE; namely in gymnasiums and residences [13].
Indus Valley
The Indus River Valley Civilization, situated in modern-day Pakistan, pioneered one of the world’s first water irrigation systems in the Bronze age (3330-1300 BCE). The civilization was known for its innovative urban planning, which saw the construction of towns on an advanced grid scheme with plumbing and sewer systems that could outmatch any pre-19th century city drainage scheme [14]. Households had access to numerous wells, and lavatories were connected to drainage systems that were directed through limestone-lined terracotta pipes to covered-drains outlining the main streets. The Indus people lessened the impact and harnessed the power of floods through complex irrigation systems, which could direct floodwater to irrigate fields [3]. Rock-cut cisterns and tanks were found in forts and along trade routes to supply potable water to tradesmen and residents [14]. The civilization’s sophisticated water management system included massive reservoirs to store and conserve rainwater in case of droughts brought on by the harsh desert climate [14].
Egypt
The first known chemical water disinfection method was seen by the Ancient Egyptians, who used gravity and alum to purify muddy water drawn from the river Nile. Ancient Egyptians mastered the coagulation disinfection technique as early as 1500 BCE [5], which used aluminum sulfate’s coagulation properties to facilitate clumping of water-suspended particles for easy filtration [4]. Irrigation ditches and canals were built around the Nile to harness its yearly floods to bring water to distant fields [5]. More specifically, the civilization used a water management system called basin irrigation: which directed floodwater to basins to sit for around a month until soil was saturated. Remaining water would be drained off into another basin in need of water, and farmers of the drained plot would plant crops in the now-fertile land. This innovative method of water management would allow Ancient Egyptians to take advantage of the Nile’s flooding for their agricultural requirements [5]. In addition, the civilization also built a system of canals for crop irrigation, which included gates to control water flow and reservoirs in preparation for droughts [5].
Modern Methods
Modern methods of water filtration make use of physical and chemical water properties. In combination with mechanical filtration, the following methods may be used to filter for a wide variety of contaminants: activated carbon, distillation, deionization, ion exchange, and reverse osmosis. Furthermore, disinfection is a more specialized process that removes contaminants and microorganisms that remain after filtration using the following methods: chlorination, UV light, and ozone [8]
Mechanical
The most basic method of water filtration involves the removal of large suspended particles through mesh filters; including sand, silt, loose scale, and organic matter [15]. As discovered by ancient civilizations, mechanical filtration is not enough to remove dissolved chemicals or very small particles, and therefore must be used in tandem with other filtration techniques [6]. Mechanical microfiltration membranes filter out certain microorganisms if the membrane pore size is sufficiently small, however the process is slow and requires frequent filter replacement [15].
Activated Carbon
Activated carbon utilizes chemical bonding or physical adsorption mainly to filter out impurities which cause aesthetic issues like bad odour and taste [6]. The activation process involves the suffusing of carbon with millions of tiny low-volume pores to increase surface area for heightened absorption or chemical reactions [7]. Chemical reactions occur between activated carbon and chlorine to produce chloride ions and effectively remove chlorine from water [7]. Alternatively, physical adsorption is the method of drawing large molecules into activated carbon pores by intermolecular forces, which works mainly on organic contaminants and pesticides. Certain minerals and salts, however, can slip through activated carbon gravels [7]. Activated carbon can be formed into carbon block filters to increase surface area, and extend filtration capabilities beyond aesthetic contaminants to dangerous pollutants such as lead, arsenic, asbestos, mercury, and radon [7].
Distillation
Distillation involves the vaporization of water by extreme heat and its subsequent condensation back to liquid [6]. Heating as a method of filtration is one of the oldest techniques; the ancient Sanskrit text “Sushruta Samhita” specifies the practices of boiling, heating under the sun, or dipping heated iron into water to keep it pure and germ-free [5]. The distillation process removes minerals, microorganisms, and chemicals with high boiling points; but cannot rid water of chlorine and more volatile organic compounds [6].
Deionization
Deionization is the promotion of ion exchange in water to remove salts and electrically-charged ions [6]. Hydrogen ions are swapped with metallic ions on an equivalent basis, then hydroxyl ions swap with remaining anions to leave behind ion-free water, wherein the remaining hydrogen and hydroxyl ions combine into more water [10]. Deionized water has applications in pharmaceutical manufacturing, and other processes where maintaining chemical soundness is critical [11]. This method of filtration does not remove microorganisms like viruses and bacteria [6].
Ion Exchange
The ion exchange filtration method uses resin to replace harmful ions (e.g. calcium and magnesium) with less harmless ions (sodium) for the purpose of softening water [6]. Though not a health hazard, hard water can damage plumbing systems by mineral buildup within pipes and fixtures. For maintaining system longevity, the resin must be regularly “recharged” with harmless replacement ions [6]. One concern is that the softened water has a high sodium level, which may be unsafe for some to consume [6].
Reverse Osmosis
Reverse osmosis is the process of forcing water through a semipermeable membrane that blocks ions, harmful molecules, and large particulates from passing [6]. During the naturally-occurring process of osmosis, water moves towards the solution with higher salt content in order to equalize salt concentration across the system [12]. The selectively-permeable membrane used in the reverse process can be engineered to stop certain chemical contaminants, like salts and metal ions. With water scarcity slowly becoming a threat, reverse osmosis can be used for desalination in order to harness the earth’s vast sources of readily-available seawater. The filtration method has its limitations; it cannot block dissolved gasses, certain organic compounds, or chlorine by-products [6].
Chlorination
Chlorination is the process of introducing chlorine or its compounds into water for the purpose of killing microbes such as bacteria and viruses, which cause water-borne diseases. Chlorine gas is introduced into water to remove almost all pathogenic microorganisms, but is toxic and cannot be used in household systems [8]. Advantages of chlorination are that it is cheaper than other methods and dosage rates are flexible and controllable. Some disadvantages are that it can impart a bad taste/odour in water, and that it can leave behind toxic byproducts through chemical reactions, some being carcinogenic [8].
UV Light
UV disinfection systems operate by breaking chemical bonds in DNA, rNA, and proteins of microorganisms [8]. The damage limits regrowth potential within water distribution systems, without the formation of any chemical by-product. As a reliable electrical supply cannot always be guaranteed, the energy requirement of a UV system can be an issue. Additionally, there are no residual effects from UV treatment, so it is only effective as a primary disinfectant. A major disadvantage is the heavy dependence of UV system efficacy on turbidity and flow rate [8].
Ozone
Ozone is a strong oxidizing agent which eliminates contaminants such as bacteria, viruses and metals [9]. The chemical works by oxidizing organic material in membranes of microorganisms (i.e. bacteria, viruses and parasites) which ruptures and kills their cells. Ozone additionally oxidizes metals (i.e. iron, manganese, and copper) into solid particles that can be filtered out mechanically. There is, however, the potential of adverse health effects from exposure to the toxic gas if a household ozone generator leaks. Being a strong oxidizer, the chemical can also corrode pipes and fixtures made of copper or galvanized metal [9].
Conclusion
Modern methods of water filtration and disinfection were clearly influenced by the innovative works of ancient civilizations. Ancient ideas such as extreme heat and coagulation have survived the test of time and served as building blocks upon which modern disinfection methods were developed. Furthermore, the extremely sophisticated ancient methods of water distribution have scarcely changed. Modern-day cities are built on drainage systems like those used in Ancient Greek and Indus Valley civilizations. Furthermore, the irrigation and water management methods utilized by ancient Mesopotamians and Egyptians for farming have been preserved over the millennia.
Today, different test methods exist for detecting various water contaminants before adverse health effects manifest. Heterotrophic plate count (HPC) is the tried and true lab method for indicating the presence of pathogenic bacteria through the detection of general heterotrophic bacteria. Mineral and pH tests show mineral buildup and acidity respectively, which inform users which treatments are necessary for water purification. The purposes of the above tests range from aesthetic (i.e. bad taste or odour) to health preservation. ExactBlue Technologies Inc. uses functionalized nanoparticles and colorimetry to provide accurate, at-home tests for various contaminants.
References:
[1]httpss://link.springer.com/book/10.1007%2F978-90-481-8632-7
[2]httpss://sciencing.com/sources-water-ancient-mesopotamia-9333.html
[3]https://indus-valley-civ.weebly.com/health-and-sanitation.html
[5]httpss://ancientengrtech.wisc.edu/ancient-egypt-water-engineering/
[6]httpss://learn.allergyandair.com/water-filters/
[7]httpss://www.carbonblocktech.com/the-science-behind-activated-carbon-water-filters/
[8]httpss://www.intechopen.com/chapters/63788
[9]httpss://www.freshwatersystems.com/blogs/blog/what-is-ozone-water-treatment-and-how-does-it-work
[10]httpss://www.freedrinkingwater.com/water-education2/49-water-di-process.htm
[11]httpss://www.total-water.com/blog/deionized-water-di-water/
[13]httpss://www.proquest.com/docview/1943127726?OpenUrlRefId=info:xri/sid:summon&accountid=13631