here limited methods meant the use of chemicals for removal of nutrients (especially phosphates and nitrates).

inputs of various researchers will be highly appreciated,

Thanks and Regards.

Depending on the case and the size of the problem, you could also think of harvesiting the (floating) vegetation in the lake on a regular basis. In most cases, this vegetation will grow abundantly with higher levels of N and P, taking up the nutrients. If you dispose the harvested vegetation elswhere, you also remove nutrients from the lake.

Closed water bodies are especially vulnerable to the introduction of invasive alien species. Avoid use, both plants and animals, because unfortunately in the majority of cases their impact in the short to medium term is usually much greater than its possible benefits. In addition there is a danger of creating a center of dispersal to other bodies of water not initially contemplated. An ecological restoration should attempt to recover both native ecosystem functions and their native species.

First priority must be to decide to invest in local species - and settle for manipulation what is already there or available locally - depending how affected your system already is

Both Tilapia and Eichornia have potentials as invasive species - in short almost ensuring that your system will never return to its original state - so don't use them if they are not already there

By the way - what do you wish to do with this manipulation??

Best regards

SoerenNN

Removing small plankton eating fish has been used in several lakes. It removes phosphorous from the system and reduces the predation on the small animals that grace on alga which increases the water clarity.

In Denmark this has been used on the large lake Furesø and in small scale in the lakes inside Copenhagen.

Read about the restoration of the Furesø in the link.

http://www.furesoe.dk/Kommunen/KlimaNaturMiljoe/Vand/SoerOgVaadomraader/Furesoe/Furesoe-Restaurering/~/media/9C8EB33EF0D44F7E95CC0D10E86431D7.ashx

@ Soren Nielsen..

Yes, certainly the local conditions will vary based on spatial and temporal variations. the baseline data can be collected. and according to that the situation has to be tackled. My keep interest is knowing about any method in which the water can be temporarily transferred into some other lagoon, given some retention time with subsequent biological treatment that would reduce to nutrient levels and then the water can be recirculated into the original water body. That can be made possible if I'm excess optimistic... !

In our region we have several ponds and tanks which have, due to anthropogenic pressure, have very high levels of nutrients. I am keenly willing to know if, by any biological means the restoration of the water bodies is possible so that we can again have those water bodies as water bodies with balanced natural structure and functions; and not merely a eutrophicated pond with a continuous film of algae floating on the water.

@ Henrik.. the link was found to be of much use..

Thanks... !

Biological restoration of a lake is possible but caution need to be taken not to introduce exotic invasive species. The link by Henrik is interesting and educating.

I'd say that the main question is if you need restoration or is it more like waste water treatment? If the catchment effect is huge and incoming water quality poor there is no use of restoring. The human impact may be too strong and override any restoration effect. If restoration is possible I'd suggest trying to take out the excess nutrients by removing them (both vegetation and small fish depending on case) like the examples from Denmark show. Then the ecosystem may have a possibility to heal by itself. I would not introduce any species which are not natural to the specific system. In small ponds some chemicals which e.g. bind phosphorus may be utilized but they do not work alone and need to take care about their other effects on the system.

Dear Manthan!

If you have that many ponds as you say, and do not want to invest in proper wastewater (WW) treatment at the point of their release into the environment, then you may use a row of the ponds to do the work. A lot is already known how to treat WW in ponds, e.g.: http://www.epa.gov/nrmrl/lrpcd/projects/ponds.htm. Usually, a series of three ponds will do excellent job.

Still, if you cannot arrange for such a facility, you shall be able to make at least partial WW treatment before the WW enters your ponds (e.g. settling and skimming). Then the first pond shall be aerated - introduce any kind of mechanical aeration you find available and satisfactory. Due to increased production in this well aerated pond, you shall drag the build-up of sediments regularly.

Phosphorus, which is the main driver of excessive growth in such ponds, shall be precipitated using one of known methods, e.g. additional oxygenation, adding of lime, adding of FeCl3. It is a good idea to pump water for precipitation from bottom of the pond where the concentration of dissolved phosphorus is the highest … and not to precipitate the whole pond water ..

Think and come back with your Q's!

Regards, Boris

One of the best method of removal of P from fresh waters is to introduce Spirodela & Lemna,which grow profusely & they can be mechanically be removed. Care needs to be taken to see that they do not decay inside the pond,as P will again get recycled.Tilapia introduction & its culture is banned in Gujarat,the state in which you are working. I agree that Tilapia will rake up pond botton. Mrigal,whose seeds are available in plenty,can be introduced,as it is a benthic feeder.Another likely fish is the "Kalbasu",whose seeds are again available in Gujarat. Another candidate is the common carp.

@ Boris. The ponds that we have were initially the natural depressions, some of which , though, were modified with the RCC boundaries. These ponds are not used for treatment of industrial waters. However, nutrients and other pollutants make their way to these ponds especially during the monsoon. I was concerned with the reduction in the concentration of such materials and substances so the pond regains its ecological stability.

@ Chandravadan Trivedi.. That was a very good piece of information.

Thanks For your inputs.. !

In some countries, I have read that vetiver can be used to remove nutrients and for phytoremediation( see www.vetivernetwork.org)

This article may be useful for you

Fish feeding from the bottom (especially the common carp) will disturb the sediment and help to release P from the sediment, so introducing them may not have the results you want.

good luck!