One of the most prominent macronutrients in aquatic systems is phosphorus which can act as a limiting nutrient or result in phytoplankton production. Excessive phytoplankton production can result in eutrophication, a condition that causes decreased dissolved oxygen concentrations and a severe reduction in aquatic life diversity. The limiting nutrient is the nutrient that exists in the lowest concentration relative to what organisms need. Many estuarine and freshwater systems, such as rivers, streams, and lakes, tend toward phosphorus limitation .Phosphorus is present in wastewater usually in a soluble form.
I mean some application of sustainable like The use of biological phosphorus removal (BPR) by a setup of aerobic zone before anaerobic zone that performs phosphorous uptake as the first step through the contact tank by absorption of phosphate as a poly-p form, then performing the biodegradation of phosphate by another aeration for return sludge (from final sedimentation zone) in stabilization tank
Carbon source may be one of the most significant factor for the BPR process. If theC/N ratio is low, the most efficient method to enhance the posphrous removal is adding soluble carbon source to the wastewater. Recently, many researchers have use the fermentation product from the waste activated sludge digestion as external carbon source. By this way, the removal of P can be enhanced, and also, the waste activated sludge can be reduced.
Aerobic zone before anaerobic?! It's cool ))
As a sorce of organic carbon you can use glycerine to increase the efficiency of P removal.
For the upgrade of an activated sludge system to remove P as well, we will first have to know the current system i.e. is it an N removal plant (e.g. MLE system)? or just organic carbon removal plant i.e. completely aerobic for COD removal and possibly nitrification only? Then from there we can upgrade the plant to also include Biological Excess P Removal (BEPR). Such configuration could be a UCT syst (N&P removal), MUCT system (N&P removal) or JHB system (N&P removal), 5-Stage Bardenpho (N&P removal) or 3-stage Bardenpho (N& P). Sometimes if you just want your plant to remove P only could choose Phoredox system (in the US called AO system).
If you want your activated sludge system to remove P you definitely cannot start with aerobic zone, that will consume all your organics as the Ordinary heterotrophic organisms (OHOs) would consume all the organics (as electron donors) to the terminal electron acceptor Oxygen in the aerated zone. Then you will need to import organics for N &P removal in subsequent steps, not very cost effective (to buy methanol and acetates etc.).
Remember the key to removing P: in the anaerobic zone of the activated sludge readily biodegradable soluble COD (RBSCOD) from feed is fermented to short chain fatty acids/volatile fatty acids (VFA) the fermented RBSCOD) together with VFAs in the influent are taken up by these Polyphosphate Accumulating ORganisms (PAOs) and they store this VFAs inside them as PHA and release P to the bulk liquid so that when they get to the aerobic zone they uptake the P again. now the uptake is higher than the release and the difference is the Removal!! These PAOs in the biomass are harvested as VSS daily based on the sludge age. this is how P is removed biologically.
To effectively remove N&P you have a system like
Anaerobic zone-Anoxic zone (for denitrification)- Aerobic zone for C removal, nitrification and P uptake.....depending on the configuration after the aerobic zone sometimes they've another secondary anoxic reactor etc...