Sigulda ( pronunciation ; German : Segewold ; Polish Zygwold) is a town in the Vidzeme region of Latvia , 53 kilometres (33 miles) from the capital city Riga .
104-433: Sigulda is on a picturesque stretch of the primeval Gauja river valley. Because of the reddish Devonian sandstone which forms steep rocks and caves on both banks of the river, Sigulda has been called the " Switzerland of Vidzeme". After the restoration of Latvian independence in 1991, an emphasis was placed on conserving Sigulda's public monuments and parks as well as improving the town's tourist sector. Supported by
208-418: A forest dynamics perspective, old-growth forest is in a stage that follows understory reinitiation stage. Those stages are: Of importance is that while the stand switches from one tree community to another, the stand will not necessarily go through old-growth stage between those stages. Some tree species have a relatively open canopy. That allows more shade-tolerant tree species to establish below even before
312-477: A free content work. Licensed under CC BY-SA 3.0 ( license statement/permission ). Text taken from The State of the World's Forests 2020. In brief – Forests, biodiversity and people , FAO & UNEP, FAO & UNEP. Water purification Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water . The goal
416-440: A "cold" electrical discharge. To use ozone as a disinfectant, it must be created on-site and added to the water by bubble contact. Some of the advantages of ozone include the production of fewer dangerous by-products and the absence of taste and odour problems (in comparison to chlorination ). No residual ozone is left in the water. In the absence of a residual disinfectant in the water, chlorine or chloramine may be added throughout
520-432: A biodiversity that is different from other forest stages. The characteristic topography of much old-growth forest consists of pits and mounds. Mounds are caused by decaying fallen trees, and pits ( tree throws ) by the roots pulled out of the ground when trees fall due to natural causes, including being pushed over by animals. Pits expose humus -poor, mineral-rich soil and often collect moisture and fallen leaves, forming
624-562: A different potential to store carbon. For example, this potential is particularly high in the Pacific Northwest where forests are relatively productive, trees live a long time, decomposition is relatively slow, and fires are infrequent. The differences between forests must, therefore, be taken into consideration when determining how they should be managed to store carbon. A 2019 study projected that old-growth forests in Southeast Asia ,
728-767: A different spatial location relative to the main canopy, hence each one receives a different amount of light. The mixed age of the forest is an important criterion in ensuring that the forest is a relatively stable ecosystem in the long term. A climax stand that is uniformly aged becomes senescent and degrades within a relatively short time to result in a new cycle of forest succession . Thus, uniformly aged stands are less stable ecosystems. Boreal forests are more uniformly aged, as they are normally subject to frequent stand-replacing wildfires. Forest canopy gaps are essential in creating and maintaining mixed-age stands. Also, some herbaceous plants only become established in canopy openings, but persist beneath an understory. Openings are
832-595: A distribution system to remove any potential pathogens in the distribution piping. Ozone has been used in drinking water plants since 1906 where the first industrial ozonation plant was built in Nice , France. The U.S. Food and Drug Administration has accepted ozone as being safe; and it is applied as an anti-microbiological agent for the treatment, storage, and processing of foods. However, although fewer by-products are formed by ozonation, it has been discovered that ozone reacts with bromide ions in water to produce concentrations of
936-563: A healthy fungal ecosystem, and presence of indicator species. Old-growth forests are often biologically diverse , and home to many rare species , threatened species , and endangered species of plants and animals, such as the northern spotted owl , marbled murrelet and fisher , making them ecologically significant. Levels of biodiversity may be higher or lower in old-growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables, and geographic variables. Logging in old-growth forests
1040-410: A moist, relatively mild climate, some old-growth trees have attained notable height and girth (DBH: diameter at breast height), accompanied by notable biodiversity in terms of the species supported. Therefore, for most people, the physical size of the trees is the most recognized hallmark of old-growth forests, even though the ecologically productive areas that support such large trees often comprise only
1144-537: A powerful oxidising agent which is toxic to most waterborne organisms. It is a very strong, broad spectrum disinfectant that is widely used in Europe and in a few municipalities in the United States and Canada. Ozone disinfection, or ozonation, is an effective method to inactivate harmful protozoa that form cysts. It also works well against almost all other pathogens. Ozone is made by passing oxygen through ultraviolet light or
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#17328478188821248-465: A primary disinfectant. When used in this manner, chloramines provide an effective residual disinfectant with very few of the negative effects of chlorination. Over 2 million people in 28 developing countries use Solar Disinfection for daily drinking water treatment. Like UV, ionizing radiation (X-rays, gamma rays, and electron beams) has been used to sterilise water. Bromine and iodine can also be used as disinfectants. However, chlorine in water
1352-609: A produce market from each of the other countries and festivals. As of 2019, its members are: Primeval forest An old-growth forest (also referred to as primary forest ) is a forest that has developed over a long period of time without disturbance . Due to this, old-growth forests exhibit unique ecological features. The Food and Agriculture Organization of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and
1456-598: A residual disinfectant in the water. Therefore, water that is boiled and then stored for any length of time may acquire new pathogens. Granular activated carbon is a form of activated carbon with a high surface area. It adsorbs many compounds including many toxic compounds. Water passing through activated carbon is commonly used in municipal regions with organic contamination, taste or odors. Many household water filters and fish tanks use activated carbon filters to purify water. Household filters for drinking water sometimes contain silver as metallic silver nanoparticle . If water
1560-689: A result of industrial logging operations. In 2006, about 61,000 hectares of tall-eucalypt RFA old-growth forests remained unprotected. Recent logging attempts in the Upper Florentine Valley have sparked a series of protests and media attention over the arrests that have taken place in this area. Additionally, Gunns Limited , the primary forestry contractor in Tasmania, has been under recent criticism by political and environmental groups over its practice of woodchipping timber harvested from old-growth forests. Increased understanding of forest dynamics in
1664-401: A result of the absorption , scattering , and shadowing caused by the suspended solids. The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water; therefore, it is sometimes necessary to add a residual disinfectant after the primary disinfection process. This is often done through the addition of chloramines, discussed above as
1768-550: A result of tree death due to small impact disturbances such as wind, low-intensity fires, and tree diseases. Old-growth forests are unique, usually having multiple horizontal layers of vegetation representing a variety of tree species , age classes, and sizes, as well as "pit and mound" soil shape with well-established fungal nets . As old-growth forest is structurally diverse, it provides higher-diversity habitat than forests in other stages. Thus, sometimes higher biological diversity can be sustained in old-growth forests, or at least
1872-432: A severe disturbance, such as wildfire, insect infestation, or harvesting, is often called second-growth or 'regeneration' until enough time passes for the effects of the disturbance to be no longer evident. Depending on the forest, this may take from a century to several millennia. Hardwood forests of the eastern United States can develop old-growth characteristics in 150–500 years. In British Columbia , Canada, old growth
1976-454: A small stream flowing from it. It is the largest cave in the Baltics , measuring 19 m (62.34 ft ) deep, 12 m (39.37 ft ) wide and 10 m (32.81 ft ) high. The cave still bears inscriptions from as early as the 17th century; drinking the water is supposed to be healthy and is said to increase one's lifespan. From the cave it is possible to climb into the hills and take
2080-486: A source of raw materials. These services include making breathable air, making pure water, carbon storage, regeneration of nutrients, maintenance of soils, pest control by insectivorous bats and insects, micro- and macro-climate control, and the storage of a wide variety of genes. The effects of old-growth forests in relation to global warming have been addressed in various studies and journals. The Intergovernmental Panel on Climate Change said in its 2007 report : "In
2184-421: A steel vessel and the water is forced through it under pressure. Advantages: Slow sand filters may be used where there is sufficient land and space, as the water flows very slowly through the filters. These filters rely on biological treatment processes for their action rather than physical filtration. They are carefully constructed using graded layers of sand, with the coarsest sand, along with some gravel, at
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#17328478188822288-412: A substrate for seedling trees. Intact soils harbor many life forms that rely on them. Intact soils generally have very well-defined horizons, or soil profiles . Different organisms may need certain well-defined soil horizons to live, while many trees need well-structured soils free of disturbance to thrive. Some herbaceous plants in northern hardwood forests must have thick duff layers (which are part of
2392-400: A thick organic layer that is able to nurture certain types of organisms. Mounds provide a place free of leaf inundation and saturation, where other types of organisms thrive. Standing snags provide food sources and habitat for many types of organisms. In particular, many species of dead-wood predators, such as woodpeckers , must have standing snags available for feeding. In North America,
2496-417: A useful number to measure. So, some forests may be excluded from being categorized as old-growth even if they have old-growth attributes just because they are too young. Also, older forests can lack some old-growth attributes and be categorized as old-growth just because they are so old. The idea of using age is also problematic, because human activities can influence the forest in varied ways. For example, after
2600-584: A very small portion of the total area that has been mapped as old-growth forest. (In high-altitude, harsh climates, trees grow very slowly and thus remain at a small size. Such trees also qualify as old growth in terms of how they are mapped, but are rarely recognized by the general public as such.) The debate over old-growth definitions has been inextricably linked with a complex range of social perceptions about wilderness preservation, biodiversity, aesthetics, and spirituality, as well as economic or industrial values. In logging terms, old-growth stands are past
2704-569: Is a by-product regulated to low allowable levels in the United States. Chlorine dioxide can be supplied as an aqueous solution and added to water to avoid gas handling problems; chlorine dioxide gas accumulations may spontaneously detonate. The use of chloramine is becoming more common as a disinfectant. Although chloramine is not as strong an oxidant, it provides a longer-lasting residual than free chlorine because of its lower redox potential compared to free chlorine. It also does not readily form THMs or haloacetic acids ( disinfection byproducts ). It
2808-414: Is a contentious issue in many parts of the world. Excessive logging reduces biodiversity, affecting not only the old-growth forest itself, but also indigenous species that rely upon old-growth forest habitat. Some forests in the old-growth stage have a mix of tree ages, due to a distinct regeneration pattern for this stage. New trees regenerate at different times from each other, because each of them has
2912-557: Is a popular cationic (positively charged) organic polymer used in water purification plants. Waters exiting the flocculation basin may enter the sedimentation basin , also called a clarifier or settling basin. It is a large tank with low water velocities, allowing floc to settle to the bottom. The sedimentation basin is best located close to the flocculation basin so the transit between the two processes does not permit settlement or floc break up. Sedimentation basins may be rectangular, where water flows from end to end, or circular where flow
3016-425: Is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite , which is a relatively inexpensive solution used in household bleach that releases free chlorine when dissolved in water. Chlorine solutions can be generated on site by electrolyzing common salt solutions. A solid form, calcium hypochlorite , releases chlorine on contact with water. Handling
3120-654: Is affected. Climate change showed an impact on the mortality of some dominant tree species, as observed in the Korean pine . Climate change also showed an effect on the composition of species when forests were surveyed over a 10- and 20-year period, which may disrupt the overall productivity of the forest. According to the World Resources Institute , as of January 2009, only 21% of the original old-growth forests that once existed on Earth are remaining. An estimated one-half of Western Europe's forests were cleared before
3224-615: Is defined as 120 to 140 years of age in the interior of the province where fire is a frequent and natural occurrence. In British Columbia's coastal rainforests , old growth is defined as trees more than 250 years, with some trees reaching more than 1,000 years of age. In Australia, eucalypt trees rarely exceed 350 years of age due to frequent fire disturbance. Forest types have very different development patterns, natural disturbances and appearances. A Douglas-fir stand may grow for centuries without disturbance while an old-growth ponderosa pine forest requires frequent surface fires to reduce
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3328-557: Is from the centre outward. Sedimentation basin outflow is typically over a weir so only a thin top layer of water—that furthest from the sludge—exits. In 1904, Allen Hazen showed that the efficiency of a sedimentation process was a function of the particle settling velocity, the flow through the tank and the surface area of tank. Sedimentation tanks are typically designed within a range of overflow rates of 0.5 to 1.0 gallons per minute per square foot (or 1250 to 2500 litres per square meter per hour). In general, sedimentation basin efficiency
3432-455: Is held in the carbon block for longer periods, microorganisms can grow inside which results in fouling and contamination. Silver nanoparticles are excellent anti-bacterial material and can decompose toxic halo-organic compounds such as pesticides into non-toxic organic products. Filtered water must be used soon after it is filtered, as the low amount of remaining microbes may proliferate over time. In general, these home filters remove over 90% of
3536-433: Is more accurate in forests where the species that constitute old-growth have long lifespans and succession is slow. Common cultural definitions and common denominators regarding what comprises old-growth forest, and the variables that define, constitute and embody old-growth forests include: Additionally, in mountainous, temperate landscapes (such as Western North America), and specifically in areas of high-quality soil and
3640-594: Is needed. Chemical and microbiological analysis , while expensive, are the only way to obtain the information necessary for deciding on the appropriate method of purification. The goals of the treatment are to remove unwanted constituents in the water and to make it safe to drink or fit for a specific purpose in industry or medical applications. Widely varied techniques are available to remove contaminants like fine solids, micro-organisms and some dissolved inorganic and organic materials, or environmental persistent pharmaceutical pollutants . The choice of method will depend on
3744-714: Is not a function of detention time or depth of the basin. Although, basin depth must be sufficient so that water currents do not disturb the sludge and settled particle interactions are promoted. As particle concentrations in the settled water increase near the sludge surface on the bottom of the tank, settling velocities can increase due to collisions and agglomeration of particles. Typical detention times for sedimentation vary from 1.5 to 4 hours and basin depths vary from 10 to 15 feet (3 to 4.5 meters). Lamella clarifiers , inclined flat plates or tubes can be added to traditional sedimentation basins to improve particle removal performance. Inclined plates and tubes drastically increase
3848-907: Is not the most commercially viable timber—in British Columbia, Canada, harvesting in the coastal region is moving to younger second-growth stands. A 2001 scientific symposium in Canada found that defining old growth in a scientifically meaningful, yet policy-relevant, manner presents some basic difficulties, especially if a simple, unambiguous, and rigorous scientific definition is sought. Symposium participants identified some attributes of late-successional, temperate-zone, old-growth forest types that could be considered in developing an index of "old-growthness" and for defining old-growth forests: Structural features: Compositional features: Process features: Old-growth forests provide ecosystem services that may be far more important to society than their use as
3952-562: Is often used. After coagulation and flocculation processes, water flows to DAF tanks where air diffusers on the tank bottom create fine bubbles that attach to the floc resulting in a floating mass of concentrated floc. The floating floc blanket is removed from the surface and clarified water is withdrawn from the bottom of the DAF tank. Water supplies that are particularly vulnerable to unicellular algae blooms and supplies with low turbidity and high colour often employ DAF. After separating most floc,
4056-472: Is over three times more effective as a disinfectant against Escherichia coli than an equivalent concentration of bromine , and over six times more effective than an equivalent concentration of iodine . Iodine is commonly used for portable water purification , and bromine is common as a swimming pool disinfectant . Portable water purification devices and methods are available for disinfection and treatment in emergencies or in remote locations. Disinfection
4160-402: Is passed quickly upward through the filter, opposite the normal direction (called backflushing or backwashing ) to remove embedded or unwanted particles. Prior to this step, compressed air may be blown up through the bottom of the filter to break up the compacted filter media to aid the backwashing process; this is known as air scouring . This contaminated water can be disposed of, along with
4264-421: Is possible to convert chlorine to chloramine by adding ammonia to the water after adding chlorine. The chlorine and ammonia react to form chloramine. Water distribution systems disinfected with chloramines may experience nitrification , as ammonia is a nutrient for bacterial growth, with nitrates being generated as a by-product. Ozone is an unstable molecule which readily gives up one atom of oxygen providing
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4368-552: Is seen as extremely economically unproductive, as timber can only be collected from falling trees, and also potentially damaging to nearby managed groves by creating environments conducive to root rot. It may be more productive to cut the old growth down and replace the forest with a younger one. The island of Tasmania , just off the southeast coast of Australia, has the largest amount of temperate old-growth rainforest reserves in Australia with around 1,239,000 hectares in total. While
4472-406: Is significant, often 3 to 5 per cent of the total volume of water to be treated. The cost of treating and disposing of the sludge can impact the operating cost of a water treatment plant. The sedimentation basin may be equipped with mechanical cleaning devices that continually clean its bottom, or the basin can be periodically taken out of service and cleaned manually. A subcategory of sedimentation
4576-644: Is that chlorine from any source reacts with natural organic compounds in the water to form potentially harmful chemical by-products. These by-products, trihalomethanes (THMs) and haloacetic acids (HAAs), are both carcinogenic in large quantities and are regulated by the United States Environmental Protection Agency (EPA) and the Drinking Water Inspectorate in the UK. The formation of THMs and haloacetic acids may be minimised by
4680-517: Is the addition of chemicals to assist in the removal of particles suspended in water. Particles can be inorganic such as clay and silt or organic such as algae , bacteria, viruses , protozoa and natural organic matter . Inorganic and organic particles contribute to the turbidity and colour of water. The addition of inorganic coagulants such as aluminium sulfate (or alum ) or iron (III) salts such as iron(III) chloride cause several simultaneous chemical and physical interactions on and among
4784-465: Is the oldest and most effective way since it eliminates most microbes causing intestinal disease, but it cannot remove chemical toxins or impurities. For human health, complete sterilisation of water is not required, since heat resistant microbes do not affect intestines. The traditional advice of boiling water for ten minutes is mainly for additional safety, since microbes start expiring at temperatures greater than 60 °C (140 °F). Though
4888-534: Is the primary goal, since aesthetic considerations such as taste, odour, appearance, and trace chemical contamination do not affect the short-term safety of drinking water. Other popular methods for purifying water, especially for local private supplies are listed below. In some countries some of these methods are used for large scale municipal supplies. Particularly important are distillation ( desalination of seawater ) and reverse osmosis. Bringing water to its boiling point (about 100 °C or 212 F at sea level),
4992-483: Is the removal of particulates by entrapment in a layer of suspended floc as the water is forced upward. The major advantage of floc blanket clarifiers is that they occupy a smaller footprint than conventional sedimentation. The disadvantages are that particle removal efficiency can be highly variable depending on changes in influent water quality and influent water flow rate. When particles to be removed do not settle out of solution easily, dissolved air flotation (DAF)
5096-611: Is to produce water that is fit for specific purposes. Most water is purified and disinfected for human consumption ( drinking water ), but water purification may also be carried out for a variety of other purposes, including medical, pharmacological, chemical, and industrial applications. The history of water purification includes a wide variety of methods. The methods used include physical processes such as filtration , sedimentation , and distillation ; biological processes such as slow sand filters or biologically active carbon ; chemical processes such as flocculation and chlorination ; and
5200-404: Is treated with lime ( calcium oxide ) and/or soda-ash ( sodium carbonate ) to precipitate calcium carbonate out of solution utilising the common-ion effect . Electrodeionization : Water is passed between a positive electrode and a negative electrode. Ion-exchange membranes allow only positive ions to migrate from the treated water toward the negative electrode and only negative ions toward
5304-446: Is usually a high energy, rapid mix unit process (detention time in seconds) whereby the coagulant chemicals are added followed by flocculation basins (detention times range from 15 to 45 minutes) where low energy inputs turn large paddles or other gentle mixing devices to enhance the formation of floc. In fact, coagulation and flocculation processes are ongoing once the metal salt coagulants are added. Organic polymers were developed in
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#17328478188825408-480: The Middle Ages , and 90% of the old-growth forests that existed in the contiguous United States in the 1600s have been cleared. The large trees in old-growth forests are economically valuable, and have been subject to aggressive logging throughout the world. This has led to many conflicts between logging companies and environmental groups . From certain forestry perspectives, fully maintaining an old-growth forest
5512-674: The Regional Forest Agreement (RFA) attempted to prevent the clearfelling of defined "old-growth forests". This led to struggles over what constitutes "old growth". For example, in Western Australia, the timber industry tried to limit the area of old growth in the karri forests of the Southern Forests Region; this led to the creation of the Western Australian Forests Alliance , the splitting of
5616-579: The boiling point decreases with increasing altitude, it is not enough to affect disinfection. In areas where the water is "hard" (that is, containing significant dissolved calcium salts), boiling decomposes the bicarbonate ions, resulting in partial precipitation as calcium carbonate . This is the "fur" that builds up on kettle elements, etc., in hard water areas. With the exception of calcium, boiling does not remove solutes of higher boiling point than water and in fact increases their concentration (due to some water being lost as vapour). Boiling does not leave
5720-522: The cable car over the river valley. The town's population has been growing every year since 2000. 86% of the population is Latvian, 9% Russian, 3% Belarusian and 2% others. Sigulda celebrated its 800th anniversary in 2007. Sigulda is a member of the Douzelage , a town twinning association of towns across the European Union . This active town twinning began in 1991 and there are regular events, such as
5824-597: The ecosystem services they provide. This can be a point of contention when some in the logging industry desire to harvest valuable timber from the forests, destroying the forests in the process, to generate short-term profits, while environmentalists seek to preserve the forests in their pristine state for benefits such as water purification , flood control , weather stability, maintenance of biodiversity, and nutrient cycling . Moreover, old-growth forests are more efficient at sequestering carbon than newly planted forests and fast-growing timber plantations , thus preserving
5928-525: The spotted owl is well known for needing standing snags for nesting habitat. Fallen timber, or coarse woody debris , contributes carbon -rich organic matter directly to the soil , providing a substrate for mosses , fungi, and seedlings , and creating microhabitats by creating relief on the forest floor. In some ecosystems such as the temperate rain forest of the North American Pacific coast , fallen timber may become nurse logs , providing
6032-532: The town council , a traditional Opera Festival takes place in an open-air music hall in the castle ruins each summer. A Town Festival is celebrated in May when cherry trees blossom, while Sigulda is known for the colors of its trees in autumn. Sports such as skiing , bobsledding , and the luge are popular in wintertime and bungee jumping is practiced during the rest of the year. The Gutmanis Cave lies halfway between Sigulda Castle and Turaida Castle and has
6136-441: The 1960s as aids to coagulants and, in some cases, as replacements for the inorganic metal salt coagulants. Synthetic organic polymers are high molecular weight compounds that carry negative, positive or neutral charges. When organic polymers are added to water with particulates, the high molecular weight compounds adsorb onto particle surfaces and through interparticle bridging coalesce with other particles to form floc. PolyDADMAC
6240-625: The Liberal Government of Western Australia and the election of the Gallop Labor Government. Old-growth forests in this region have now been placed inside national parks . A small proportion of old-growth forests also exist in South-West Australia and are protected by federal laws from logging, which has not occurred there for more than 20 years. In British Columbia , Canada , old-growth forests must be maintained in each of
6344-446: The atmosphere. Proponents of harvesting the forest argue the carbon stored in wood is available for use as biomass energy (displacing fossil fuel use), although using biomass as a fuel produces air pollution in the form of carbon monoxide , nitrogen oxides , volatile organic compounds , particulates, and other pollutants, in some cases at levels above those from traditional fuel sources such as coal or natural gas. Each forest has
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#17328478188826448-399: The boiling solution. Even distillation does not completely purify water, because of contaminants with similar boiling points and droplets of unvapourised liquid carried with the steam. However, 99.9% pure water can be obtained by distillation. Direct contact membrane distillation (DCMD) passes heated seawater along the surface of a hydrophobic polymer membrane. Evaporated water passes from
6552-763: The bottom and the finest sand at the top. Drains at the base convey treated water away for disinfection. Filtration depends on the development of a thin biological layer, called the zoogleal layer or Schmutzdecke , on the surface of the filter. An effective slow sand filter may remain in service for many weeks or even months, if the pretreatment is well designed, and produces water with a very low available nutrient level which physical methods of treatment rarely achieve. Very low nutrient levels allow water to be safely sent through distribution systems with very low disinfectant levels, thereby reducing consumer irritation over offensive levels of chlorine and chlorine by-products. Slow sand filters are not backwashed; they are maintained by having
6656-404: The chlorine in a glass of treated water. These filters must be periodically replaced otherwise the bacterial content of the water may actually increase due to the growth of bacteria within the filter unit. Distillation involves boiling water to produce water vapour . The vapour contacts a cool surface where it condenses as a liquid. Because the solutes are not normally vaporised, they remain in
6760-640: The concentrate stream is fed to the RO inlet. Disinfection is accomplished both by filtering out harmful micro-organisms and by adding disinfectant chemicals. Water is disinfected to kill any pathogens which pass through the filters and to provide a residual dose of disinfectant to kill or inactivate potentially harmful micro-organisms in the storage and distribution systems. Possible pathogens include viruses , bacteria, including Salmonella , Cholera , Campylobacter and Shigella , and protozoa , including Giardia lamblia and other cryptosporidia . After
6864-584: The ecological processes are not significantly disturbed. One-third (34 percent) of the world's forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife habitats that increases the biodiversity of the forested ecosystem . Virgin or first-growth forests are old-growth forests that have never been logged. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris. As of 2020 ,
6968-421: The economic optimum for harvesting—usually between 80 and 150 years, depending on the species. Old-growth forests were often given harvesting priority because they had the most commercially valuable timber, they were considered to be at greater risk of deterioration through root rot or insect infestation, and they occupied land that could be used for more productive second-growth stands. In some regions, old growth
7072-473: The effective removal of as many organics from the water as possible prior to chlorine addition. Although chlorine is effective in killing bacteria, it has limited effectiveness against pathogenic protozoa that form cysts in water such as Giardia lamblia and Cryptosporidium . Chlorine dioxide is a faster-acting disinfectant than elemental chlorine. It is relatively rarely used because in some circumstances it may create excessive amounts of chlorite , which
7176-436: The forest will switch back to understory reinitiation stage. Using the stand dynamics definition, old-growth can be easily evaluated using structural attributes. However, in some forest ecosystems, this can lead to decisions regarding the preservation of unique stands or attributes that will disappear over the next few decades because of natural succession processes. Consequently, using stand dynamics to define old-growth forests
7280-472: The forests is vital to climate change mitigation . Old-growth forests tend to have large trees and standing dead trees, multilayered canopies with gaps that result from the deaths of individual trees, and coarse woody debris on the forest floor. The trees of old-growth forests develop distinctive attributes not seen in younger trees, such as more complex structures and deeply fissured bark that can harbor rare lichens and mosses. A forest regenerated after
7384-424: The geology of the drainage basin or aquifer and the influence of contaminant inputs ( acid rain ). If the water is acidic (lower than 7), lime , soda ash , or sodium hydroxide can be added to raise the pH during water purification processes. Lime addition increases the calcium ion concentration, thus raising the water hardness. For highly acidic waters, forced draft degasifiers can be an effective way to raise
7488-399: The hot side through pores in the membrane forming a stream of cold pure water on the other side. The difference in vapour pressure between the hot and cold side helps to push water molecules through. Reverse osmosis involves mechanical pressure applied to force water through a semi-permeable membrane . Contaminants are left on the other side of the membrane. Reverse osmosis is theoretically
7592-465: The intended use of the water. A visual inspection cannot determine if water is of appropriate quality. Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all possible contaminants that may be present in water from an unknown source. Even natural spring water —considered safe for all practical purposes in the 19th century—must now be tested before determining what kind of treatment, if any,
7696-422: The introduction of any chemical disinfecting agent, the water is usually held in temporary storage – often called a contact tank or clear well – to allow the disinfecting action to complete. The most common disinfection method involves some form of chlorine or its compounds such as chloramine or chlorine dioxide . Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Because chlorine
7800-427: The landscape patterns and habitat conditions normally maintained in nature . This coarse filter approach to biodiversity conservation recognizes ecological processes and provides for a dynamic distribution of old growth across the landscape. And all seral stages—young, medium, and old—support forest biodiversity. Plants and animals rely on different forest ecosystem stages to meet their habitat needs. In Australia ,
7904-525: The late 20th century led the scientific community to identify a need to inventory, understand, manage, and conserve representative examples of old-growth forests with their associated characteristics and values. Literature around old growth and its management is inconclusive about the best way to characterize the true essence of an old-growth stand. A better understanding of natural systems has resulted in new ideas about forest management, such as managed natural disturbances, which should be designed to achieve
8008-617: The local Regional Forest Agreement (RFA) was originally designed to protect much of this natural wealth, many of the RFA old-growth forests protected in Tasmania consist of trees of little use to the timber industry. RFA old-growth and high conservation value forests that contain species highly desirable to the forestry industry have been poorly preserved. Only 22% of Tasmania's original tall-eucalypt forests managed by Forestry Tasmania have been reserved. Ten thousand hectares of tall-eucalypt RFA old-growth forest have been lost since 1996, predominantly as
8112-408: The logging of 30% of the trees, less time is needed for old-growth to come back than after removal of 80% of the trees. Although depending on the species logged, the forest that comes back after a 30% harvest may consist of proportionately fewer hardwood trees than a forest logged at 80% in which the light competition by less important tree species does not inhibit the regrowth of vital hardwoods. From
8216-413: The long term, a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber, fibre, or energy from the forest, will generate the largest sustained mitigation benefit." Old-growth forests are often perceived to be in equilibrium or in a state of decay. However, evidence from analysis of carbon stored above ground and in
8320-476: The majority of which are in Indonesia and Malaysia , are able to sequester carbon or be a net emitter of greenhouse gases based on deforestation scenarios over the subsequent decades. Old-growth forests have the potential to impact climate change, but climate change is also impacting old-growth forests. As the effects of global warming grow more substantial, the ability of old-growth forests to sequester carbon
8424-475: The pH, by stripping dissolved carbon dioxide from the water. Making the water alkaline helps coagulation and flocculation processes work effectively and also helps to minimise the risk of lead being dissolved from lead pipes and from lead solder in pipe fittings. Sufficient alkalinity also reduces the corrosiveness of water to iron pipes. Acid ( carbonic acid , hydrochloric acid or sulfuric acid ) may be added to alkaline waters in some circumstances to lower
8528-459: The pH. Alkaline water (above pH 7.0) does not necessarily mean that lead or copper from the plumbing system will not be dissolved into the water. The ability of water to precipitate calcium carbonate to protect metal surfaces and reduce the likelihood of toxic metals being dissolved in water is a function of pH, mineral content, temperature, alkalinity and calcium concentration. One of the first steps in most conventional water purification processes
8632-539: The particles. Within seconds, negative charges on the particles are neutralised by inorganic coagulants. Also within seconds, metal hydroxide precipitates of the iron and aluminium ions begin to form. These precipitates combine into larger particles under natural processes such as Brownian motion and through induced mixing which is sometimes referred to as flocculation . Amorphous metal hydroxides are known as "floc". Large, amorphous aluminium and iron (III) hydroxides adsorb and enmesh particles in suspension and facilitate
8736-400: The positive electrode. High purity deionised water is produced continuously, similar to ion-exchange treatment. Complete removal of ions from water is possible if the right conditions are met. The water is normally pre-treated with a reverse osmosis unit to remove non-ionic organic contaminants , and with gas transfer membranes to remove carbon dioxide . A water recovery of 99% is possible if
8840-517: The province's ecological units to meet biodiversity needs. In the United States , from 2001, around a quarter of the federal forests are protected from logging. In December 2023, Biden's administration introduced a rule, according to which, logging is strongly limited in old growth forests, but permitted in "mature forests", representing a compromise between the logging industry and environmental activists. In 2006, Greenpeace identified that
8944-526: The quality of the water being treated, the cost of the treatment process and the quality standards expected of the processed water. The processes below are the ones commonly used in water purification plants. Some or most may not be used depending on the scale of the plant and quality of the raw (source) water. Pure water has a pH close to 7 (neither alkaline nor acidic ). Sea water can have pH values that range from 7.5 to 8.4 (moderately alkaline). Fresh water can have widely ranging pH values depending on
9048-521: The removal of particles by subsequent processes of sedimentation and filtration . Aluminum hydroxides are formed within a fairly narrow pH range, typically: 5.5 to about 7.7. Iron (III) hydroxides can form over a larger pH range including pH levels lower than are effective for alum, typically: 5.0 to 8.5. In the literature, there is much debate and confusion over the usage of the terms coagulation and flocculation: Where does coagulation end and flocculation begin? In water purification plants, there
9152-404: The river. Membrane filters are widely used for filtering both drinking water and sewage . For drinking water, membrane filters can remove virtually all particles larger than 0.2 μm—including Giardia and Cryptosporidium . Membrane filters are an effective form of tertiary treatment when it is desired to reuse the water for industry, for limited domestic purposes, or before discharging
9256-607: The shade-tolerant species and regenerate the canopy species. In the boreal forest of Canada , catastrophic disturbances like wildfires minimize opportunities for major accumulations of dead and downed woody material and other structural legacies associated with old growth conditions. Typical characteristics of old-growth forest include the presence of older trees, minimal signs of human disturbance, mixed-age stands, presence of canopy openings due to tree falls, pit-and-mound topography , down wood in various stages of decay, standing snags (dead trees), multilayered canopies, intact soils ,
9360-404: The sludge from the sedimentation basin, or it can be recycled by mixing with the raw water entering the plant although this is often considered poor practice since it re-introduces an elevated concentration of bacteria into the raw water. Some water treatment plants employ pressure filters. These work on the same principle as rapid gravity filters, differing in that the filter medium is enclosed in
9464-403: The smallest suspended particles, so simple filtration is not enough. Most particles pass through surface layers but are trapped in pore spaces or adhere to sand particles. Effective filtration extends into the depth of the filter. This property of the filter is key to its operation: if the top layer of sand were to block all the particles, the filter would quickly clog. To clean the filter, water
9568-462: The soil has shown old-growth forests are more productive at storing carbon than younger forests. Forest harvesting has little or no effect on the amount of carbon stored in the soil, but other research suggests older forests that have trees of many ages, multiple layers, and little disturbance have the highest capacities for carbon storage. As trees grow, they remove carbon from the atmosphere, and protecting these pools of carbon prevents emissions into
9672-516: The soil profile). Fungal ecosystems are essential for efficient in-situ recycling of nutrients back into the entire ecosystem. Stand age can also be used to categorize a forest as old-growth. For any given geographical area, the average time since disturbance until a forest reaches the old growth stage can be determined. This method is useful, because it allows quick and objective determination of forest stage. However, this definition does not provide an explanation of forest function. It just gives
9776-473: The solid, however, requires more routine human contact through opening bags and pouring than the use of gas cylinders or bleach, which are more easily automated. The generation of liquid sodium hypochlorite is inexpensive and also safer than the use of gas or solid chlorine. Chlorine levels up to 4 milligrams per litre (4 parts per million) are considered safe in drinking water. All forms of chlorine are widely used, despite their respective drawbacks. One drawback
9880-436: The surface area available for particles to be removed in concert with Hazen's original theory. The amount of ground surface area occupied by a sedimentation basin with inclined plates or tubes can be far smaller than a conventional sedimentation basin. As particles settle to the bottom of a sedimentation basin, a layer of sludge is formed on the floor of the tank which must be removed and treated. The amount of sludge generated
9984-501: The suspected carcinogen bromate . Bromide can be found in fresh water supplies in sufficient concentrations to produce (after ozonation) more than 10 parts per billion (ppb) of bromate—the maximum contaminant level established by the USEPA. Ozone disinfection is also energy intensive. Ultraviolet light (UV) is very effective at inactivating cysts, in low turbidity water. UV light's disinfection effectiveness decreases as turbidity increases,
10088-404: The top layer of sand scraped off when the flow is eventually obstructed by biological growth. In bank filtration , natural sediments in a riverbank are used to provide the first stage of contaminant filtration. While typically not clean enough to be used directly for drinking water, the water gained from the associated extraction wells is much less problematic than river water taken directly from
10192-549: The understory reinitiation stage. The shade-tolerant trees eventually outcompete the main canopy trees in stem-exclusion stage. Therefore, the dominant tree species will change, but the forest will still be in stem-exclusion stage until the shade-tolerant species reach old-growth stage. Tree species succession may change tree species' composition once the old-growth stage has been achieved. For example, an old boreal forest may contain some large aspen trees, which may die and be replaced by smaller balsam fir or black spruce. Consequently,
10296-652: The use of coagulants. The type of membrane media determines how much pressure is needed to drive the water through and what sizes of micro-organisms can be filtered out. Ion exchange : Ion-exchange systems use ion-exchange resin - or zeolite -packed columns to replace unwanted ions. The most common case is water softening consisting of removal of Ca and Mg ions replacing them with benign (soap friendly) Na or K ions. Ion-exchange resins are also used to remove toxic ions such as nitrite , lead, mercury , arsenic and many others. Precipitative softening : Water rich in hardness ( calcium and magnesium ions)
10400-513: The use of electromagnetic radiation such as ultraviolet light . Water purification can reduce the concentration of particulate matter including suspended particles , parasites , bacteria, algae , viruses, and fungi as well as reduce the concentration of a range of dissolved and particulate matter. The standards for drinking water quality are typically set by governments or by international standards. These standards usually include minimum and maximum concentrations of contaminants, depending on
10504-463: The water into a river that is used by towns further downstream. They are widely used in industry, particularly for beverage preparation (including bottled water ). However no filtration can remove substances that are actually dissolved in the water such as phosphates , nitrates and heavy metal ions. Ultrafiltration membranes use polymer membranes with chemically formed microscopic pores that can be used to filter out dissolved substances avoiding
10608-403: The water is filtered as the final step to remove remaining suspended particles and unsettled floc. The most common type of filter is a rapid sand filter . Water moves vertically through sand which often has a layer of activated carbon or anthracite coal above the sand. The top layer removes organic compounds, which contribute to taste and odour. The space between sand particles is larger than
10712-471: The world has 1.11 billion ha (2.7 billion acres) of primary forest remaining. Combined, three countries (Brazil, Canada, and Russia) host more than half (61 percent) of the world's primary forest. The area of primary forest has decreased by 81 million ha (200 million acres) since 1990, but the rate of loss more than halved in 2010–2020 compared with the previous decade. Old-growth forests are valuable for economic reasons and for
10816-413: The world's remaining intact forest landscapes are distributed among the continents as follows: [REDACTED] This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 ( license statement/permission ). Text taken from Global Forest Resources Assessment 2020 Key findings , FAO, FAO. [REDACTED] This article incorporates text from
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