January 10th, 2010
A waterhole on a drying creek in Central Victoria The water is very discoloured and has an earthy smell with abundant protozoans and a few algae The ORP value (oxygenation) has dropped to the low side of the desirable range.
At Apps Laboratories we measure a range of factors in water samples. Some like dissolved metals can be compared directly to the Australian Water Quality Guidelines. Others like salinity indicate what the water can be used for for example depending on the salt tolerance of irrigated crops. More often we want to give the landowner an idea of what is wrong with the water; an indicator of ‘health’ or quality.
This gives a better understanding of management of the water or possible treatments. Here is what we found in a recent dam water sample. The water has a smell like compost and was discoloured green by algae. A quick check of ORP level showed very low oxygenation. High ammonia (unionized form) confirmed that there was probably high organic contamination of the water and that under low oxygen conditions some was being converted to ammonia. We also didn’t find any nitrates but this was expected because of the low oxygen. UVA absorbance was very high further suggesting high levels of organics in the water. The water also had elevated salts and a calculated significant sodium hazard.
Very high densities of algae usually indicate high nutrient inputs. The fact that we found some phosphate was a bit worrying as algae usually use up all the phosphate as they grow. Perhaps a check on the water coming into the dam would be recommended. The water was also very alkaline (pH 9.2). Algal blooms remove carbon dioxide especially during the day and send the pH upwards. At night the pH should return to more normal levels. There were two unusual characteristics of this water; the pH stayed high overnight and there was higher than expected alkalinity. Some of this water is waste water from a food processing plant.
Overall the ‘quality’ was low and several problems were indicated both in the source water and in the stored water.
Tags: Drought, Farm water supplies, Irrigation water, water quality, water testing
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August 21st, 2009
One of the problems with many homes in rural areas is that there is not enough pressure from pressure pumps to run a reverse osmosis filter system. Reverse osmosis filters work by pushing water against a very fine membrane. Only a proportion of the water, usually 1/4 to 1/3 gets through, leaving behind most salts and other contaminants. The rest of the water with the contaminants goes to waste.
A boosted RO system for rural homes.
RO systems are designed to remove a large proportion of most contaminants from water including salts and chemicals. The result is very clean water. RO works more efficiently with reasonably clean water like rain water tank or spring water.
The picture is of a boosted RO I made up. It is in the lab and produces rinsing water for the lab and also drinking water for the house. Output is about 108 l/d. It uses a 24 gpd membrane. 50 gpd membranes are also commonly used. The prefilter is just a 1 micron sediment cartridge. The second cartridge is a 1 micron carbon block cartridge. This cartridge is designed to reduce tastes, smells and protozoan pathogens. Here are some results for the lab RO system.
|
Before filter |
After filter |
| DOC* by UVA 254 nm |
2.1 ppm |
0 |
| Conductivity |
87 microS/cm |
7.4 microS/cm |
* DOC = Dissolved Organic Carbon. DOC is directly proportional to UVA at 254 nm for most waters. Here an estimate of DOC is made based on an approximate relationship derived from published data from a variety of waters.
There are no detectable dissolved organics getting through and the salts level has been significantly reduced. RO membranes can also reduce bacteria in the water but I haven’t tested bacteria reduction yet.
For a range of water filters to suit both town and country applications see Water Doctor water filters.
Tags: Farm water supplies, Reverse osmosis, Water filters, water quality
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August 17th, 2009
Last weekend I joined a few of my ex Rover friends from the Yallourn Capt Hurley Rover Crew on a trip up “The Mountain”. The mountain is Mt Erica in Gippsland. Most of us are in our late 50’s or early 60’s. We have mostly known each other for over 40 years.
Our numbers were a bit down this year but here are the diehards at the summit of Mt Erica.
The Captain Hurley Rover crew built the JW McMahon hut on Mt Erica over many years starting from 1938. Its a basic but comfortable mountain retreat. It has given generations of scouts and other groups the opportunity to take time out in a relatively unspoilt and remote area in a safe way. From Mt Erica we can look down on the expansive Latrobe Valley with its several coal fired power stations. So close but a world away. The water on the mountain tends to be fairly clear with relatively low numbers of bacteria. In other similar hilly areas I’ve measured low organics in water using UV but this is mostly humic material.
There wasn’t much snow around this year. Global warming perhaps? Its often difficult to use scientific knowledge to prove that one factor is causing another so arguments tend to go round in circles. In the medical field there have been attempts to move towards a type of diagnosis that attempts to describe the patient’s current ’situation’ and to infer how the patient’s overall condition has developed. Its like trying to explain something and the explanation is a model that is further tested and refined. Part of that refinement is through the treatments themselves. Perhaps environmental problems could be tackled the same way.
We spent a pleasant couple of days together with no electricity (well except for batteries to play the iPod), no emails, no showers and only the company of Boris the resident Lodge rat.
Tags: Global warming, water quality, Yallourn
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July 5th, 2009
Recently a couple of bore water samples came through the lab. By coincidence although they came from very different locations they had some distinct similarities. These were elevated dissociated carbon dioxide, elevated soluble iron and elevated manganese. But they both had another similarity – low ORP or redox value. The sample with the highest metal levels had an ORP of around 110 mV. In the other the ORP was around 160 mV. I usually expect ORP levels of between 200 – 400 mV in good quality water.
ORP is a measure of oxidizing capacity. A low ORP especially below 0 indicates reducing conditions. In the sample above with the lowest ORP I aerated the water with an aquarium pump for 5 hrs but could only get the ORP to around 300 mV. After that it slipped back to around 200 mV. What an ORP probe measures is the average effect of usually many different redox reactions pulling the mV value up and down. Oxygen supply is thought to mainly influence higher ORP values but lower values are created by reduction of oxygen supplying species (molecules / substances) such as sulphate and oxides of metals like iron and manganese.
For more detail on why measuring redox is important please see pH and ORP in water.
Tags: water quality, water testing
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June 13th, 2009
Water testing is a little bit like problem solving. Most people want to know if there are any underlying issues that may affect their water quality. For example if there are higher than expected numbers of bacteria, if there are dissolved metals present or if there is any contamination from organic chemicals. Most test results are ‘indicators’ and go towards characterising water quality. They also give some ideas about both water treatment, for example by using water filters or, often more importantly water supply management.
There are a lot of things that can possibly be in water: algae and microorganisms, organic chemicals, metals, different salts and dissolved gases. But water is not a static system – it is a living (usually) system that has its own properties. One of the most useful tests I do in the lab is to measure carbon dioxide. Specifically its the dissociated fraction that is part of the pH buffer system. By also measuring alkalinity its possible to calculate a theoretical pH. Now when that’s compared to the actual pH some inferences can be made about factors that are affecting water quality. Something similar is done in medicine where analysis of the pH buffer system can indicate if a persons illness is affecting or originating from kidneys or lungs.
Tags: water, water quality, water testing
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