A lake has been significantly affected by land-use activities and loaded with nutrients, I want to design experiment to extract the nutrients from the lake water (nutrient contaminated water) for reuse by farmers.
it depends what nutrients you want to analyze. Metals can be analyzed using Atomic Absorption Spectroscopy.
Cheers,
Riteshma.
Dear Ishmael Lente
May i know what is the purpose of extracting those nutrients?
This is because different technique may have different effect toward the extracted nutrient.
If you are going to conduct a physical based experiment, you may need a good sample of extracted nutrient with minimum alteration.
Based on my experience, the most simplest method is to take the water sample and try to exclude the presence of H20 by drying it.
Depends upon which nutrients. Obviously you can use ion exchange; however, you will end up concentrating other anions (chloride, sulfate) which will reduce the usefulness of your attempt to extract them.
One way I have used in indigenous population areas (low technology) is to take advantage of the nutrient loading to grow aquatic plants, then harvest the plants as a solid biosource that can be plowed back into the fields. Hyacinths are exceptionally good at this, and then become an excellent source of nitrogen and phosphorus. You do have to be careful if the lake is also high in metals, as hyacinths will quite effectively concentration trace elements.
If your lake is eutrophic, as you indicate, then you probably already have a source of algal biomass that can be harvested and dried. Again, this is a high quality solid form of organic fertilizer that can be returned to the land.
Thank you all for your excellent answers. But, Mark, you may send to me papers in the area to help in my work. The main idea is resource recovery in terms of Nitrogen and Phosphorus recovery for local farmers. Thank you. Hope to get some papers from on this area.
A simple biological system analogous to a sewahe treatment plant would probably work - after all, sewage is simply water with a wide range of nutrients in it. The simplest sysem would probably be a biological filter; you could start with a filter using coarse material such as small pebbles, say 5-10 mm diameter. A biofilm would build up on the filtration material removing the nutrients bjt this would take a little time, but it would make a a simple and ideal experiment as a starting point. The optimum micro-organisms would appear over a period of time although it might be possible to seed the filter with, for example, the effluent from a sewage treatment plant, although I suspect that the lake already has a suitable population of micro-organisms. It might be helpful to analyse the nutrients to make sure they have the optimum P/K/N balance, and if not you might need to dose either P K or N to the filter ijnfluent to optimise the micro-organism activity in the filter.
Thank you for your excellent answer. You may suggest papers to me, if any.
I would be inclined simply to try a few simple experiments. You might find something of iterest in BIOLOGICAL FIXED FILM SYSTEMS, Wei Lin, Tong Yu, Belinda S. McSwain and Yanlin S. He. Water Environment Research Vol. 76, No. 6, Literature Reviews (2004), pp. 1099-1154 Pub. by: Water Environment Federation. Also you could try textbooks such as the Water Treatment Handbook published by Degremont which has sometjhing on the use of filtration for treating wastewater (ie the removal of unwanted substances in water) and also Wastewater Engieering by Metcalf and Eddy, pub. McGraw-Hill. Look up, for example, packed bed reactors and fluidised bed reactors as well as simple filtration. You also need to consider aerobic and anaerobic processes. If the N is present as nitrate then an anaerobic system might be required. This could entail using two or more filters in series, each one dedicated to removing a particular type of pollutant; one being anaerobic and another being aerobic.
In New Zealand floating wetlands have been trialled on lakes and such trials found there had been good absorption of nutrients. In principle, nutrient removals should be efficient. Depending on the local demand, you can use a number of plants. You could grow certain plants on such wetlands and feed livestock. Watercress could be another useful plant that could be used for human consumption. Please follow the attached link to see the methodology (http://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCEQFjAA&url=http%3A%2F%2Fwww.massey.ac.nz%2F~flrc%2Fworkshops%2F11%2FManuscripts%2FTanner_2011.pdf&ei=XeW5VO3qAc6C8gWdwoH4Cw&usg=AFQjCNGGUFdqHEY7pNP7fsVqGiCz-llGQw&sig2=a6qlk79zAV-pkMvkR4qM3A&bvm=bv.83829542,d.dGc).
Why do you wish to extract them?
1) For commercial recycling?
2) For chemical analysis?
An answer to this will help to focus the replies.
The floating treatment wetland idea is one that is used in stormwater ponds throughout the US - and would be effective (probably even better) for agricultural uses - where it seems your nutrient loading rate is even higher. It's all in developing your scaffold to support the aquatic plants and then figuring out how to manage harvest, composting the plant material (or direct land application). The nutrients held in the plant tissues should be released slowly - while the organic matter would help with soil health. Some FTW papers/resources
If the nutrients in lake water are enough more to use them as fertilizer for plants then the requirement of crop can be meet out by irrigating withlake water. the no of irrigation will depend on the concentration of nutrients in lake water and can be easily calculated.
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