Posts Tagged ‘farm water’

Farm water supply investigation

Saturday, January 25th, 2014

A preliminary investigation was carried out on the quality of water in two dams on a dairy farm in West Gippsland. The dams are a short distance apart in the same gully. The Upper dam is spring fed and can overflow into the Lower dam. The water was tested during summer. At that time the flow into the Upper dam had decreased and the water level was falling. The Lower dam was still fairly full.

The dams are in an elevated position and drain approximately 10 ha. The surrounding land is pasture.

Farm dam in West Gippsland. The Upper dam in this study. Water is pumped around the farm for drinking water for stock and also for washdown water in the dairy.

Farm dam in West Gippsland. The Upper dam in this study. Water is pumped around the farm for drinking water for stock.

There are many waterbirds on the dams – mainly ducks. Cows have access to both dams and commonly drink at the water’s edge. The water in both dams has a pale yellow-brown colour. There is significant attached bacterial – fungal mats clearly visible in shallow water.¬† One significant observation was that were no visible micro crustaceans.

Dam CO2 EC Turbidity Reactive C ORP*
ppm microS/cm FTU mg/L mV
Upper 18 289 11.5 0.5 207
elevated sl. elevated sl. cloudy moderate OK
Lower 5.8 738 3.5 0.5 205
moderate elevated clear moderate OK
* oxidation reduction potential

Some key findings are: Dissociated carbon dioxide was high in the Upper dam. The water is fairly clear in both dams with the Upper dam water just slightly cloudy. Overall salts as conductivity are elevated in the Lower dam. Both dams have oxidizing potential (a surrogate for oxygen level) within the desirable range.

Reactive or relatively fresh organic matter was estimated by permanganate digestion. In both dams reactive organic matter was in the moderately elevated range. Humic material in dams can be measured indirectly by UV absorbance. In both dams the UV absorbance was high, around 65%.

The pH of the Upper dam was 7.2 and pH of the Lower dam was 6.8. A pH buffer system analysis of the Upper dam gives a calculated pH of 6.7. This suggested the scenario of a falling pH (water becoming more acidic) as the carbon dioxide level rises. In this case the rise in carbon dioxide is being most likely caused by increasing organic matter decomposition. See organic matter figures below.

A pH buffer system analysis for the Lower dam gives theoretical pH of 7.84. This suggests that carbon dioxide level in this water is falling and this will cause the pH to slowly rise (the water will become more alkaline).

Farm dam in West Gippsland. This is the Lower dam in the study. Some physical and chemical factors show some improvement compared to the Upper dam. However there levels of the 3 key bacteria water quality indicator groups are twice the levels compared to the Upper dam.

Farm dam in West Gippsland. This is the Lower dam in the study. Some levels of physical and chemical factors are more favourable compared to the Upper dam. However the levels of 3 key bacteria water quality indicator groups are around twice the levels of the Upper dam.

Dam E. coli coliforms TC*
CFU’s / 100 ml CFU’s / 100 ml CFU’s / 100 ml
Upper 440 3317 53281
elevated** high moderate
Lower 960 7119 118274
elevated** elevated** sl. elevated
* aerobic plate count
** indicates contamination

For both dams the high  E coli level taken along with the high coliform levels indicate some fecal contamination of the water. Total aerobic bacteria level is approximately in the moderate range for exposed waters.

The main quality issue in both dams is elevated reactive organic matter levels and elevated E coli bacteria levels. There is some evidence that processes in the Lower dam are at least slowing deterioration of water quality. However on the negative side, levels of bacteria are significantly higher in the Lower dam.

Ideally in a study like this it would be useful to test the source water, in this case the spring water entering the dams. Unfortunately the spring was not accessible. There was also no other dam on the property to provide a comparison.

Effluent management on a dairy farm

Saturday, November 9th, 2013

For the last few weeks I’ve been visiting a dairy farm in West Gippsland to learn a bit more about how dairy farms work. It’s also an opportunity to apply some ideas about soil and water management in a practical context.

Cows can deposit around 8 – 10% of manure and urine output around the milking shed and yards. Manure and urine contains significant amounts of major nutrients including nitrogen, phosphorous and potassium.

On many farms this manure is often washed directly into specially contructed waste retention dams. A typical setup is a sedimentation dam sometimes followed by an aeration dam.

Sedimentation dam for dairy waste on a farm in West Gippsland. Water is washed into the dam from the milking shed and yards without treatment.

Sedimentation dam for dairy waste on a farm in West Gippsland. Water is washed into the dam from the milking shed and yards without treatment.

The picture shows a sedimentation dam on the WG farm. There is a thick crust of manure on top which means that conditions in the dam are most likely anaerobic. At this dam I didn’t want to get too close in case I became part of the waste system! Therefore I didn’t get a sample!

In an anaerobic dam the organic matter itself provides oxygen to help drive the other processes that eventually break down most of the organic matter into methane, hydrogen, carbon dioxide and ammonia. But the disadvantage of this method is that energy in the organic matter is lost (as methane) and importantly nitrogen is lost (as ammonia).

The overflow from the sedimentation dam on the farm enters a second aeration dam. What can we expect the water quality to be in this type of dam? There shouldn’t be much nitrogen but what other nutrients will be present?

Dairy farm aeration dam in West Gippsland. Water flows into this dam from an uphill sediantation dam that takes waste directly from the dairy.

Dairy farm aeration dam in West Gippsland. Water flows into this dam from an uphill sedimentation dam that takes waste directly from the dairy.

The aeration dam is just below the sedimentation dam. The overflow pipe can be seen in the picture. The water has a brown colour and a slightly unpleasant smell. Here are some water quality tests done in the Apps Labs lab: Dissociated carbon dioxide 13.5 ppm (elevated); Turbidity (unfiltered) 57 FTU (high); Turbidity filtered (0.45 micron) 19.8 FTU (still high); pH 7.1 (very slightly on the alkaline side); UV absorbance 99.2% (very high dissolved humic materials); Conductivity 1459 microS/cm (elevated salts); redox potential (ORP) -44.7 mV (anaerobic, and that’s at the surface).

Nitrate and nitrite were checked using screening tests. Both were at low levels or absent. That’s expected anyway because nitrates usually don’t exist in low oxygen conditions and nitrites usually form from nitrates under reducing conditions. Phosphate was checked using two different test kits. One showed phosphate over 30 ppm. The other showed phosphate as 43 ppm. Both these levels are very high.

There may be significantly more phosphate present in the two dams than the amount measured as some is likely to be held in the sediments.

What about nitrogen? Ammonia – nitrogen in the aeration dam was 0.44 ppm. This is higher than normally found in natural waters but is not excessive. At pH 7 around 0.4% of this nitrogen can be expected to be in the ammonia form as opposed to the ammonium form. This is not good for water life because the ammonia form is harmful. In general as water becomes more alkaline, an increasing amount of any total ammonia nitrogen present is likely to be in the ammonia form. This same amount of ammonia nitrogen, is roughly equivalent to 2 ppm nitrogen as nitrate. This is slightly elevated for natural waters so the nitrogen in the ammonia form probably doesn’t account for all the nitrogen in the original manure entering the two dams.

What is the best way to use dairy effluent to capture maximum nutrient value?

The following web resource provides detailed figures on tests done on dairy effluent dams and suggests way to reuse the nutrients in the effluent:

DPI Victoria 2013, Using dairy effluent as a fertilizer. Downloaded from http://www.dpi.vic.gov.au/agriculture/dairy/pastures-management/fertilising-dairy-pastures/chapter-13, November 2013.

Filters for farm water supplies.

Saturday, December 8th, 2012

Not all water quality problems for farm and rural drinking water can be solved by simple filters. However there is a lot that can be done to improve drinking water quality. Its often a matter of being proactive in case contamination occurs. Dual cartridge systems are easy to install and can often be fitted under the kitchen sink. The choice of cartridges depends on the source of the water.

Above ground or well protected rainwater tanks usually don’t build up bacteria levels but they can develop undesirable smells if poorly aerated. Use a sediment cartridge and a 5 micron carbon cartridge. At Apps Laboratories we have selected some dual cartridge combinations that can be applied to different situations. See them at Drinking water systems.

If you have to backup your water supply from a creek or dam then use a sediment cartridge plus a finer carbon cartridge, one that is designed to reduce waterborne protozoan pathogens. Your carbon cartridge should reduce some turbidity so that UV treatment can be added. UV is very effective against bacteria provided there is not too much dissolved organic matter in the water. Ask Apps Laboratories for a Basic water quality test.

Many farms source water from fairly protected situations like springs or bores. But there may be fine silt or sediment and a risk from bacteria. Again a fine carbon cartridge like the KX Matrikx Cr1 is recommended. The second cartridge will be a special ceramic cartridge such as the Doulton Sterasyl. Ceramic cartridges are very effective at reducing bacteria. At Apps Laboratories we have tested ceramic cartridges and the results are reported in Ceramic cartridge test.

Doulton Sterasyl ceramic cartridge for bacteria reduction.

Doulton Sterasyl ceramic cartridge for bacteria reduction.

For more details on Rural and farm drinking water systems please see Rural and farm systems.