November 22, 2013

On the Nature of Water: vii) Water Treatment

    Flush. Swirl. Swoosh – bye. Ever wonder where that goldfish ended up when you were 12 years old? Indoor plumbing is something that we have all gotten used to – the day of the outhouse is over … for the moment. The sewer systems use water as the great sweeper – the idea that the solution to pollution is dilution really caught on during the post WWII era. We flush and run and rarely give thanks for the notion of a hot shower in the morning.
   The municipal waste treatment plants dot the rivers in place just before every hamlet. The residents count on this cleansing process to bring them cool, clear water – bacteria and odor free. The chemical treatments of the water remain out of sight and out of mind – until the process breaks down and we get yuck. Lets cover some of the standard processes of waste-water treatment.
   The first process is filtration. This is accomplished by having screens on the collection port – which keeps the larger stiff like branches, rocks and fish out of the water intake system. A smaller set of screens may be behind the larger ones – screen mesh size dictates how much small material can be removed. There is always some material that gets through – the test for total suspended solids tells us that amount. The test is rather simple – pour a liter of water through a dry, carefully weighed filter paper, in a Buchner funnel using a side-arm filter flask and a water aspirator. The pressure pulls the water through the paper and the solid materials are measured by weighing the filter paper again, after it is dry.

    Water is routinely tested for basic physical parameters. The clarity of the liquid is measured as turbidity. A small sample is placed in a cell in a light box with a carefully measured path-length. The light is measured and compared to a path that has a cell with cloudiness, but no water. The comparators are made from a gel which has known n.t.u – nephalometric turbidity units. The standards are purchased in sealed vials and run at the same time as the samples.

    The pH and Conductivity are also measured. The pH is a measure of the acidity of water – placed on a logarithmic scale with units between one and fourteen. Seven is considered neutral and desirable, lower numbers imply that the water is acidic – higher numbers correspond to basic. River and stream waters tend to average about pH 7.3 – the actual pH is a function of the type of land that the water runs through. Conductivity is a measure of the ionic conductance through the solution – which increases as a function of salt dissolved. The more conductivity, the more percentage of salt in the water. The ocean is composed of salt water – natural water runs the gamut of values, depending on the solubility of the salts of the earth.

    The conductivity can be related to the total dissolved solids. To measure total dissolved solids requires taking a liter of water to complete dryness and weighing the residues. The combination of both the suspended solids and the dissolved solids together make the total solids of the material. High turbidity increases TSS without affecting TDS. Usually, salts dissolved in the water will not have much effect.

    However – hard water is material that has a lot of dissolved calcium and magnesium salts, which can cause problems with washers and water heaters by causing scale. Scale happens when precipitates come out of solution to take up solid capacity within the containers, plumbing or pipes. Some people use water filters to remove this scale, the medium being either activated carbon, sand or an ion-exchange resin. These filters have a limited capacity based on their size and have to be monitored for break-through, at which time a new filter can be substituted for the old one.

    Sometimes – municipal water systems will use flocculation and sedimentation in large tanks to clean up the water. This process involves mixing a chemical with the water that adsorbs the other materials hat are caught in the solution. Lime is a typical flocculant. The tank water is stirred with lime then allowed to settle – the water is then decanted off the solid lime, which has all the impurities adhered to the surface. The settling is important – the flocculant would otherwise plug the flow pipes. The size of the tanks are over thousands of gallons – there is an economy of scale in treating large batches of water, when continuous flow methods are not available.

    The temperature of the water is also a water quality parameter. Fish tend to be very sensitive to temperature change. Hot water also tends to dissolve more materials than colder water, but really – the temperature of running water only varies when the inputs are either direct sun/shade or a large industrial system. Many times – the water released by factories is not controlled locally. The waterways are used as waste carriers and the industries are 'permitted' to use the rivers as sewers because 'that is the way things have always been done'. This is not cool, but try complaining and you get to be a target. The Erie River near Pittsburgh once caught fire from the additional waste additions. Don't get me started on acid mine drainage.

    Another fairly important test is for fecal coliform. This is the live bacterial material found in animal poop – as expressed in the form of e-coli. E-coli is the biggest evil on the planet – killing unsuspecting patrons of unsanitary restaurants. Only it is not – it is common stomach bacteria that comes in many forms and rarely lives outside of stomachs for very long. Finding e-coli in water systems is a big red flag – but it is always found in natural water systems, where animals haven't figured out indoor plumbing. One cow pattie is fine for nailing a farmer whose fields have run off, yet the municipal systems tend to put out poor quality water, while getting a pass.

    The EPA with its clean water act is more responsible for polluted waters than anyone – it gives permission to pollute up to certain levels to people that own the system – George Carlin style. Don't kid yourself – the water game is a game of control just like the back-story to the movie Chinatown implies. If you own the water rights, you still have to service the government that insists that you buy the water however they deliver it. It comes with residual chlorine at the end of the tap. Thus, in the Monsane whirled, the way to mitigate for coliform seems to be to add a bigger toxin to kill the coliform – mask the problem and poison you. It helps to aerate municipal tap-water for about an hour before drinking – or boil the water to remove the volatile impurities.

    We have not even begun the rant on fluoridation, but alas – our essay space has expired for another day. Keep yourself hydrated with good water. 

Namaste' ... doc  

PS - Doc cannot control when the paragraph is bold or not bold.  There is no ulterior motive in the print style.

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