Desalination – is a process by which saline water (generally sea water) is converted to fresh water. The most common desalination processes are distillation and reverse osmosis. Desalination is currently expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination. It is only economically practical for high-valued uses (such as household and industrial uses) in arid areas.

Ion exchange:[11] 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 Ca2+ and Mg2+ 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.
Most reverse osmosis systems require you to do a bit of under-sink installation and drill a hole for a separate dispenser, but you can also opt for a countertop model that saves your cabinet space and won’t require any drilling. The APEC Portable Countertop Reverse Osmosis Water Filter System can be set up quickly and easily with no permanent installation necessary.

Electrodeionization:[11] 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 the positive electrode. High purity deionized 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 the concentrate stream is fed to the RO inlet.
The first step calls for the installation of 2 push fit elbows. Note these were the only two elbows that leaked on me, despite use of thread tape and applying what I felt was the right torque. You really need to seat elbows well with the top of the male tread well below the plane of the housing. The push fits are of the type that once you push the poly tube in, that's it. So, being they are elbows, there is no coming back to easily address leak at the body joint. (I had NO push fit leaks in the system)... DONT Panic if it leaks at the body. Very careful removal of the inline filter and the RO membrane ... full review
What’s unique about the tankless design of the RCS5T is the fact that each time you fill a glass with water or a pot for cooking, the water is purified on demand. As a result, you may notice that it fills slightly slower and with less water pressure than similar systems, but you’ll know that the water has been freshly filtered and hasn’t been sitting in a storage tank.

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 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.[8]:74–5
Photo by Philip ChoiPlan a menu ahead of time and keep things as simple as possible. The type and amount of food you carry will vary, depending on whether you are traveling in a vehicle or hiking deep into the wilderness on foot. If you are carrying everything on your back, pack dry and dehydrated foods that you can prepare with hot water. A large variety of pre-packaged meals are available at most camping stores, or you can make them at home. A small bottle of oil, seasonings, granola bars, summer sausage, jerky, and crackers are also good options.

The remineralization stage is an additional feature of this water purifier. The name itself explains the function of this stage. After passing through the basic 5 stages of filtration the water is treated in the remineralization stage. At this point of purification, some advantageous minerals restored into the water again. The added minerals improve the taste and raise the pH to more alkaline. You will definitely enjoy the fresher tasting mineral water.
Reverse osmosis: Mechanical pressure is applied to an impure solution to force pure water through a semi-permeable membrane. Reverse osmosis is theoretically the most thorough method of large scale water purification available, although perfect semi-permeable membranes are difficult to create. Unless membranes are well-maintained, algae and other life forms can colonize the membranes.
We all know that dehydration can be dangerous, leading to dizziness, seizures, and death, but drinking too much water can be just as bad. In 2002, 28-year-old runner Cynthia Lucero collapsed midway through the Boston Marathon. Rushed to a hospital, she fell into a coma and died. In the aftermath it emerged that she had drunk large amounts along the run. The excess liquid in her system induced a syndrome called exercise-associated hyponatremia (EAH), in which an imbalance in the body's sodium levels creates a dangerous swelling of the brain.
A reverse osmosis water purification unit (ROWPU) is a portable, self-contained water treatment plant. Designed for military use, it can provide potable water from nearly any water source. There are many models in use by the United States armed forces and the Canadian Forces. Some models are containerized, some are trailers, and some are vehicles unto themselves.[citation needed]
This system can purify up to 50 gallons of water per day and has 5 stages of filtration to remove up to 99 percent of TDS. For every gallon of purified water produced, there are 3 gallons of wastewater. This is an average conversion rate and is much better than some water filtration systems that have 4 or 5 gallons of wastewater for every purified gallon produced.
Installation went very well, although the manual was generic and not specific to the model I bought. This made the assembly a little longer as there were no specific photos pertaining to the 7 stage unit. Unit comes 95% assembled and all fittings installed. All interconnecting tubing is precut and most is preassembled. The included universal adapter fittings for your plumbing made drain hookup a snap. Total install under the sink took about 3 hours (drilling, electric, etc.). Don't forget the electric outlet! Zero leaks after install. As the instructions say, the first few cups of water will come out quite warm because water surrounds the ultraviolet sterilizer bulb and it is always on. Great for tea or coffee, less microwave time. Let it run for 10 seconds and you're good. I am getting about 2.5 gallons out of the unit before pressure drops. It still puts out after that, ... full review
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water 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 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 the use of electromagnetic radiation such as ultraviolet light.
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 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.

A specific "large-scale" form of slow sand filter is the process of bank filtration, in which natural sediments in a riverbank are used to provide a 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 the river.
Direct contact membrane distillation (DCMD). Applicable to desalination. Heated seawater is passed along the surface of a hydrophobic polymer membrane. Evaporated water passes from the hot side through pores in the membrane into 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.
In recent years, energy consumption has dropped to around 3 kWh/m3, with the development of more efficient energy recovery devices and improved membrane materials. According to the International Desalination Association, for 2011, reverse osmosis was used in 66% of installed desalination capacity (0.0445 of 0.0674 km³/day), and nearly all new plants.[19] Other plants mainly use thermal distillation methods: multiple-effect distillation and multi-stage flash.
Only a part of the saline feed water pumped into the membrane assembly passes through the membrane with the salt removed. The remaining "concentrate" flow passes along the saline side of the membrane to flush away the concentrated salt solution. The percentage of desalinated water produced versus the saline water feed flow is known as the "recovery ratio". This varies with the salinity of the feed water and the system design parameters: typically 20% for small seawater systems, 40% – 50% for larger seawater systems, and 80% – 85% for brackish water. The concentrate flow is at typically only 3 bar / 50 psi less than the feed pressure, and thus still carries much of the high-pressure pump input energy.