THEMATIC ISSUEThe effects and mechanism of alkalinity on the phosphaterecovery from anaerobic digester effluent using dolomite limeXueyu Liu 1,2,3 • Liancheng Xiang 2,3 • Yonghui Song 1,2,3 • Feng Qian 2,3 •Xiaoguang Meng 4Received: 15 November 2014/Accepted: 23 March 2015/Published online: 4 April 2015? Springer-Verlag Berlin Heidelberg 2015Abstract The alkalinity plays an important role inphosphate removal. Precipitate in the Mg 2? –Ca 2? –NH 4 ? –PO 4 3- system has been researched to understand thephosphate recovery from anaerobic digester effluent. Thisproject investigated the usefulness of a chemical equilib-rium model, Visual Minteq3.0, for prescribing the ionicform of CO 2 . In the present study, a series of jar test wasconducted using dolomite lime (DL) to evaluate the func-tion of alkalinity during the precipitate reaction. Over arange of PO 4 3- –P (20, 60, and 120 mg/L), the addition ofalkalinity (0–8 g/L) was found to decrease the removal rateof phosphate. However, the result showed that the impactwas definite when the maximum of inhibition reached. Theremoval rate of phosphate reduced 4.80, 11.49 and 9.19 %under the effect of alkalinity. The recovered products weredetected and analyzed by X-ray diffraction, scanningelectron microscope and energy dispersive spectrometer,which were proved to be struvite and calicite. Finally, ourexperiment showed that the struvite precipitation waskinetically favored over hydroxyapatite. The precipitationmechanisms in the DL-treated wastewater were researchedand explained by the kinetic experiment.Keywords Phosphate ? Recovery ? Alkalinity ?MechanismIntroductionIn recent years, with the rapid economic growth and indus-trial development of Chinese, it has brought tremendouspressure on the environment (Young et al. 1999).Eutrophication of freshwater sources is a widespread globalpollution issue. Wastewater discharges of nitrogen andphosphorustotheenvironmentareundesirablebecausethesenutrientsaccelerateeutrophication(Leeetal.2003).Surveysreveal that around 50 % of all the lakes and reservoirs in allthe continents barring Africa and Oceania are eutrophic. Inthe USA, an EPA study found that 36 % of the lakes areeutrophic (USEPA 1997). In China, the surface water of thewhole country is light pollution and eutrophication in majorlakesisstillratherserious.Forexample,amongthe469state-controlled sections of the ten biggest water systems from thestate of the Environment Bulletin China (2011), the mainpollution factors were COD, BOD 5 and TP.Despite the environmental and health benefits of limitingnutrient discharges, there is a continuing need to supply ni-trogen and phosphorus to agriculture and industry. Phos-phorusisanon-renewablesource(Sugiyamaetal.2014)andis primarily available from phosphate rock, high-qualitydeposits of which are controlled by just five countries.By the end of 2010, 2832 wastewater treatment plants(WWTPs) had been built in china and the capacity ofsewage treatment was 150 million. However, 22.6 % rawcity sewage discharged directly, and it would cause& Yonghui Songsongyh@craes.org.cn1College of Water Sciences, Beijing Normal University,Beijing 100875, People’s Republic of China2State Key Laboratory of Environmental Criteria and RiskAssessment, Chinese Research Academy of EnvironmentalSciences, Beijing 100012, People’s Republic of China3Department of Urban Water Environmental Research,Chinese Research Academy of Environmental Sciences,Beijing 100012, People’s Republic of China4Center for Environmental Engineering, Stevens Institute ofTechnology, Hoboken, NJ, USA123Environ Earth Sci (2015) 73:5067–5073DOI 10.1007/s12665-015-4335-5
