PHOSPHATE DETERMINATION

[srose]

I am doing a project in the lab to determine the phosphate concentration of a water sample. There are so many steps involved. Can someone point me in the right direction. I know that I will be making a reagent using 2.5g ammoniun molybdate in 30ml distilled water.Then mixing 0.125g ammonium metavandate in 30ml water, heating it, cooling it, then adding 33ml HCL. Then I will mix them and dilute to 100ml with water. What is this reagent for, when will I be needing it?
Then I have to prepare my standard phosphate sample using Anhydrous KH₂PO₄. How do I do this? And what is standard being used for?
Then I have to prepare my samples. How is this done? why am I having to prepare my samples? They are on liquid form already, hence, water is my sample. Then the procedure talks about sample digestion or acidifying the sample. Why is this being done, do I have to do digestion for a tap water sample?

I AM COMPLETELY LOST ON THIS WHOLE PROJECT. I HAVE SPENT THE LAST WEEKS READING EVERY WEBSITE ON THIS LAB. thEY ARE ALL CONFUSING SINCE THEY ARE ALL DOING DIFFERENT THINGS AND USING DIFFERENT TECHNIQUES. I NEED SOME HELP, PLEASE!