Dear All,
I am working on an experiment in which I used industrial effluent to grow water hyacinth.
I was just wondering if I could use an effluent stirring system (continuously) to facilitate maximum exposure of pollutants to the roots of plant?
What is the possibility of this process being it be helpful and feasible?
With Regards
Pankaj
https://www.sciencedirect.com/search?qs=continuous%20effluent%20stirring&show=25&sortBy=relevance
This is not my expertise. I think it might depend on the type of pollutants, and it one were to assume the plant uptakes the pollutants through root system, and many pollutants attach and adhere to sediments, excessive mixing may dislodge sediments and pollutants, or prevent settling of some fine particles such as clay size are very slow to settle. Water hyacinth is a wetland plant I believe, rooting into permanently flooded or hydric soils with likelihood of anaerobic conditions in soil. Some pollutants may not break down well in anaerobic conditions. For example, we had a railroad spill of ethylene glychol (antifreeze) into a wetland, it would not break down until oxygen was injected. In that instance, circulation and injecting oxygen would probably be good. I suppose one must consider if the plant is uptaking, removing or breaking down the pollutants, or is it the flooded, hydric conditions with some combination of aerobic and anaerobic conditions for bacteria, sunlight, photosysthesis, etc. And how much is retained in the soil, or moved and diluted laterally or into groundwater.
Dear William F. Hansen Sir,
I retained the plants for a period of 28 days. I often observed that if I do not mix the effluent, the particles coagulates/sediments on the bottom of the aquariums, which decreases the net exposure of the pollutant to the plant.
If not native to your area, it may be considered invasive and nuisance if released. It sounds like you have a well controlled system, and probably if floating, most of the roots are not attached to bottom, so mixing increases the exposure and uptake as suggested.
Dear Kumar, any kind of stirring will surely enhance pollutant reduction from wastewater, but it should not be continously process rather a weekly affair. Continous stirring will affect biofilm attached to plant roots.
Dear M. Ashraf Bhat Sir,
What If I reduce the stirring speed to very low? Like 4 inch long propeller impeller at a speed of 30 rpm only?
I have worked with water hyacinths for water pollution control for over thirty years. Aerating the root zone is helpful in that it can increase the diversity of the root zone ecosysem, and also facilitate nitrification within the root zone. However unless your water is high in oxygen demand, aeraion or stiring may not be worth the money. Hyacinth roots do slough at a high rate, and any system to have long tem success needs to include a means to priodically recover the sediment accretion. Probably the most important operational need is to maintain a healthy standing crop of about 3-5 wet lb/sf through frequent harvesting. Typically a mean plant age of 21-28 days works well and will result in optimal producivity and nutrient uptake. This of course depends upon initial water quality. Modeling can be done using first order kinetics associated with the Monod equation applied on an ecosystem level--more engineering than pure science.
Respected Allen Stewart,
Thank you very much for such a helpful answer.
Dear M. Ashraf Bhat,
I have a small (lab scale) setup. Aquariums of 40 L capacity horizontal.
stirring helps in aeration and in turn helps in mixing up the pollutants and helps in reaching the roots and thereby helps Phytoremediation.
Dear Dr.PK. Your querry is well addressed by Dr. Allen Stwrt (3d ago). I too hv exprnc in phyto r for mncpl ww . We apply the process for total HRT 8-9 days. At 1st is anaerobc.3d hrt followed by anaerbc with 2 lvl fltrs 3d hrt. At the 3rd stage use phyto r wth nrml plnts- cayhna indca or elphnt grss.Hv done on floats with plants too. Wind, solar direct exposure if present is very useful. Elphnt grss is harvstd regularly for feed for pigs and ducks reared by SHGs/ community. Rglr hrvstng and deweeding of el. grss is done. Thus the process is sustained and income generating.etc. My detailed paper on DEWATS process and design is in RG web site.. you may refer to same.. w wshs. Prof. Ajit Seshadri. Vels University. Chennai. INDIA.
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