What Is Raw Water?

Introduction

Raw water is natural water in its environment that has not been treated with minerals, ions, particles, or bacteria and parasites removed.  Sources of raw water include rain water, ground water, infiltration wells and water from lakes and rivers.  Rain water that has not been treated is used for farming, construction and cleaning purposes. 

Farmers use raw water for watering crops, giving it to livestock to drink and storing it in man-made lakes and reservoirs.  Construction companies make cement and dampen unsealed roads to keep the dust from rising.  Raw water is also used to flush toilets and wash cars when it is not consumed by humans.  What is considered raw water as opposed to water that is treated before drinking water is used during the industrial process for wastewater.  Raw water for flushing toilets is used for water conservation.

Composition

Raw water is made of humic acid and other complex acids for plant decay that occurs in peat and soil.  But this makes the water discolored.  Minerals that make water hard are common carbonates called calcium and magnesium.  But raw water also contains clay and silt particles as well.  It may also contain microorganisms like bacteria, viruses and protozoa and their cysts.  One such microorganism is Vibrio cholerae, an infectious bacteria in contaminated water.  Dissolved air molecules like oxygen are also present in raw water.  And what makes water brackish, or more salinity in freshwater—yet not as much as seawater—is salt. 

There could be less common contaminants in raw water like natural radioactive particles, one of which could be Perfluorinated alkyl acid, an perfuorooctanic acid that belongs to a group of pollutants found in the wastewater in Europe.  These chemicals can contaminate raw water used for drinking water. 

Endocrine disruptor compounds also interfere with the endocrine system and can cause cancerous tumors, birth defects and developmental disorders.  This can make it harmful to humans for drinking water containing them if not treated before. 

It also has an effect on the ecosystem as well as it can be harmful to fish populations who swim in natural lakes and rivers.  The growing health concerns have set guideines by the Hazard Analysis and Critical Control Points (HACCP) to produce safe drinking water, wastewater, rainwater as well as further their research for a sustainable water supply alternatives.

Treatment

There are many purposes of raw water which include cooling water, water for rinsing, chemical production and drinking water.  But due to contaminants, raw water must be treated before human consumption and industrial use.  These steps involved have different methods that take place.

Reverse Osmosis

Reverse osmosis has been used to demineralize water for 30 years.  It is water that is transported through a membrane of high pressure, leaving the product that consists of water and its concentrate containing minerals and unwanted residues.  Contaminants like iron, manganese, ammonium, traces of pesticides and medicines, organic micro-pollutants and radioactive particles can also be removed by reverse osmosis as well.  This is the primary method of water purification, but it is also used in combination with other methods as well.  The disadvantage to reverse osmosis is the removing of many minerals and giving drinking water a bad taste—the main reason water is added with minerals to improve its taste.

Conditional Pre-Treatment

This method is a compex, multistage process that has been used for many years and includes five steps.  The first step is adjusting the alkalinity and pH, in addition to hydrated lime and carbon dioxide.  The second step is removing matter that has congregated like aluminum sulphate and coagulants and polymers.  The third step is to mix clarifiers that will reach the larger partices that have setteled to the bottom of rivers and lakes to remove sedimentation.  The fourth step is to direct water clarifiers to the filters like anthracite and sand filters to trap the smaller particles that survive the clarification process.  And the fifth step is to add sodium hydroxide to adjust the pH and alkalinity, sodium hypochlorite for disinfection and fluorid for fluoridation.  Conditional pre-treatment is mainly used as a pre-treatment, whereas reverse osmosis as a final treatment. 

A disadvantage to this method is the use of chemicals like ozone, flocculents, hydrogen peroxide, lime, chlorine for the filtration process.  If these chemicals are used incorrectly, it could be dangerous if left in the water after treatment.  Each step requires special precautions to achieve the controlled optimal performance.  But the need for a complex control system in a conventional treatment is financially costly, but may lead to developing alternative pre-treatment methods for raw water.

Ultrafiltration

The method of ultrafiltration is a membrane filtration process that provides an alternative to the conventional pre-treatment.  The water is pre-filtered through a common screen filter before being filtered through a high pressure membrane that separates water contaminants.  It is used for water in pre-treatment and reverse osmosis.  The advantages to ultrafiltration are a very high water quality that is independent of initial contaminants in raw water.  It is a simple plant that is designed more flexibly to make it easier automatically and lower the use of chemicals as a final product that is free of viruses and microorganisms.

Bio-Film Pre-Treatment and Bio-Diatomite Dynamic Membrane Reactor

This method is used to remove harmful chemical by-products like NH4+_N, a total Nitrogen, that is dissolved in organic matter to form a disinfection process.  It is a necessary step in many parts of the word for low operation in cost and effectiveness for pollutant removal.  Microorganisms remove contaminants in raw water and wastewater that are harmful to humans except nutrients.  It combines a dynamic membrane technology in wastewater treatment for microbial colonies to form diatomite particles that purify the water.  It is under development in China to address the country’s pollution problems.

Turbidity

Turbidity is the murkiness or haziness of water due to suspended particles.  The more suspended particles, the higher the turbidity.  It is used to measure quality of water.  Raw water is common for turbidity.  High amounts of turbidity in raw water is mainly due to an increased flow of heavy rain fall, a spring turnover in water masses, bank erosion, sediment resuspension in shallow areas and a temporary increase from more turbid areas.

Turbidity and Health Concerns

Pathogens found in raw water are high turbidity peaks that can contribute to the spread of illness.  It has increased hospital visits, especially for the elderly (65+) for gastronintestina illnesses.  Even places where there is a water filteration in place that meets standards has been known to cause an endemic of gastrointestinal illness on waterborne infectious diseases.  But the hospitalized only represent a small fraction of the total morbidity causing illnesses.

Controlling Turbidity

The best way to control and reduce turbidity is to control the land surrounding raw water.  Areas that are high in sediment resuspension and erosion need to be attended frequently with screened devices to catch suspended particles.  These screens trap debris, but need to be consistently cleaned as well, and flush out water pumps should be done when the demand is lowest.  The best time is when the water has settled and turbidity decreases before the needed amounts.  Turbidity reduction can be best achieved when water is run as a series of chemical and physical treatment methods before it reaches the filter.

Claimed Health Benefits

Producing clean drinking water and a reduction in water borne illnesses is responsible for huge improvements in human life expectancy in the U.S. and other industrialized countries.  Untreated spring water is naturally probiotic raw water where it is distributed as a commercial product by many health food shops.  But the concerns on public health have a possible occurrence of harmful bacteria, viruses and parasites (Giardia).  Despite a safe, reliable water supply in the U.S., people can be phobic when it comes to clean water and often reject the benefits of adding fluoride to drinking water, which strengthens teeth, in low doses.   Many U.S. raw water businesses claim that spring water producers have changed the molecular structure of water.