Why is there a need for increased recycling to preserve phosphorus? (20 points) what technique was used to measure the availability of phosphorus for plants in sewage sludge? (15 points) what is a disadvantage of using thermally conditioned sewage

Answer 1) : The phosphorus minerals deposits that are currently available is not enough for the future, and the distribution of the ores are also uneven throughout the globe. The major part of food production are also dependent on the production of phosphorus. Phosphorus is also widely used as fertilizer and most of the population of farmers are dependent on it. This has increased the need to preserve and save the phosphorus.

Answer 2) : To measure the current availability of phosphorus found in plants of thermally conditioned sewage sludge, phosphorus radiotracer technique was used and the present amount of phosphorus was determined. A study of experiment in ryegrass was done in pots whcih were filled with soil that underwent isotopic P-labelling, and no fertilizer was added, thermally conditioned sewage sludge as fertilizer. Then shoot and roots were harvested at definite fixed intervals, and their radioactivity was analyzed to measure phosphorus uptake.

Answer 3) : Although there is no major disadvantage of using thermally conditioned sewage sludge as a fertilizer but they incur a great cost on their maintenance and operation, along with this they produce strong odors which is not possible to get rid off, they also generate large amount of liquor waste; handling and safe disposal of that is quite difficult. Continuous physical conditioning has to be given.

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