Technologies to Remove Phosphorus from Wastewater

Converting a non-P removing activated sludge to EBPR by acclimatization toalternating anaerobic and aerobic conditions takes 40-100 days, but many EBPR systemsexperience start-up failure or breakdown (Dabert et al., 2005). Bioaugmentation(inoculating with previously adapted microorganisms) was found to speed up the processfor a laboratory SBR by about 15 days compared to a non-augmented control.Optimization of dissolved oxygen, sludge age, and nitrate-N concentration forefficient phosphorus removal were tested at an A2O wastewater treatment plant in Guilin,China, (Li et al., 2005). Results showed that DO must be controlled in the anaerobicphase, nitrate-nitrogen concentration must be decreased in the anaerobic section, and asludge age of 8-10 days was preferable to 15 days.Kuba et al. (1997) examined the role of denitrifying phosphorus removingbacteria (DPB) in wastewater treatment plants using batch tests with activated sludgefrom two plants in the Netherlands. DPBs appeared to be of little importance in oneplant, but contributed substantially to P removal in the other.D. Sludges and Side StreamsThere is some concern about the effects of solids management processes andreturn side streams on the ability to remove P to low levels. Processes that destroyorganic material (such as digestion) have the potential to release the particulate organic-Ppresent as soluble organic or inorganic P. In particular, anaerobic conditions are likely torelease soluble P from EBPR sludges and iron precipitates (ferrous phosphate is muchmore soluble than ferric phosphate). Any released P may then be returned to the mainwastewater treatment process in high concentrations through recycle side streams, thusrequiring removal a second time. Non-continuous processes may also lead to variableloadings from side streams. A number of these issues were discussed by Narayanan(2006).In some cases, these problems, particularly with anaerobic digestion, have notbeen as severe as originally anticipated, or could be controlled (deBarbadillo, 2006).This appears in part to be related to the formation of the mineral struvite, MgNH 4 PO 4 .Struvite has long been known for its potential to cause clogging in anaerobic digesters(Vaccari et al., 2006), where ammonium and phosphate are released as the organic matteris degraded. However, it appears that formation of this mineral in digesters at EBPRplants may lead to its precipitation as small granules that remain with the sludge, ratherthan the release of soluble P to the supernatant where it would be recycled. This isapparently enhanced by the liberation of Mg 2+ by PAOs as a major associated cationduring phosphate release (Liao et al., 2003).Another approach is to remove the P from the recycle stream. Britton et al.(2005) demonstrated treatment of anaerobic digester supernatant in pilot scale using afluidized bed reactor. Phosphate was recovered in the form of struvite through theaddition of magnesium chloride and pH adjustment. Liao et al. (2003) looked at releaseof P directly from EBPR sludge by several methods for possible P recovery. Takiguchi et5

al. (2004) tested thermal (70 ◦ C) treatment followed by precipitation with Ca in a labscale.AcknowledgmentsI would like to thank Erin Murphy and Amy Boyajian for their contributions tothis review.Literature CitedAkin, B.S. and A. Ugurlu. 2003. Biological removal of carbon, nitrogen and phosphorusin a sequencing batch reactor. Journal of Environmental Science and Health, 38, 1479-1489.Awuah, E., M. Oppong-Peprah, H.J. Lubberding, and H.J. Gijzen. 2004. Comparativeperformance studies of water lettuce, duckweed, and algal-based stabilization pondsusing low-strength sewage. Journal of Toxicology & Environmental Health, 67, 1727-1739.Barnard, J. 2006. Requirements for achieving effluent phosphorus of less than 0.1 mg/L.Session P1 in WERF, 2006.Britton, A., F.A. Koch, D.S. Mavinic, A. Adnan, W.K. Oldham, and B. Udala. 2005.Pilot-scale struvite recovery from anaerobic digester supernatant at an enhancedbiological phosphorus removal wastewater treatment plant. Journal of EnvironmentalEngineering & Science, 4, 265-277.Dabert, P., J.P. Delgenes, and J.J Godon. 2005. Monitoring the impact ofbioaugmentation on the start up of biological phosphorus removal in a laboratory scaleactivated sludge ecosystem. Applied Microbiology & Biotechnology, 66, 575-588.deBarbadillo, C. 2006. Biological phosphorus removal at the McDowell Creek WWTP.Session P1 in WERF, 2006.Emrick, J. 2006. Cold weather BNR limits. Session P1 in WERF, 2006.Hermanowicz, S. 2006. Chemical fundamentals of phosphorus precipitation. Session P2in WERF, 2006.Kuba, T., M.C.M. van Loosdrecht, F.A. Brandse, and J.J. Heijnen. 1997. Occurrence ofdenitrifying phosphorus removing bacteria in modified UCT-type wastewater treatmentplants. Water Research, 31, 777-786.Li, J., H. Ren, X. Wang, Q. Liu, and Q. Xie. 2005. Technique for biological phosphorusremoval. Pollution Engineering, 37, 14-17.Liao, P.H., D. Mavinic, and F.A. Koch. 2003. Release of phosphorus from biologicalnutrient removal sludges: A study of sludge pretreatment methods to optimizephosphorus release for subsequent recovery purposes. Journal of EnvironmentalEngineering & Science, 2, 369-381.Littleton, H.X., G.T. Daigger, P.F. Strom, & R.M. Cowan. 2000. Evaluation ofautotrophic denitrification and heterotrophic nitrification in simultaneous biological6