Struvite recovery from municipal-wastewater sludge centrifuge supernatant using seawater NF concentrate as a cheap Mg(II) source

TY - JOUR

T1 - Struvite recovery from municipal-wastewater sludge centrifuge supernatant using seawater NF concentrate as a cheap Mg(II) source

AU - Lahav, Ori

AU - Telzhensky, Marina

AU - Zewuhn, Annette

AU - Gendel, Youri

AU - Gerth, Joachim

AU - Calmano, Wolfgang

AU - Birnhack, Liat

N1 - Funding Information: This project was funded by the Joint German-Israeli Water Technology Research Program (BMBF/MOST) and the Israel Science Foundation.

PY - 2013

Y1 - 2013

N2 - The paper describes the application of an alternative method for generating struvite (MgNH4PO4) solids from wastewater, using a low-cost Mg(II) solution, previously separated from seawater by nanofiltration (NF). Mg2+ ions are present at high concentrations in the oceans (∼1400 mg/L) and are well rejected by nanofiltration membranes, therefore, NF enables obtaining a concentrate that is rich in Mg(II) at a low cost. Since the largest cost component in conventional methods for struvite precipitation from wastewaters stems from the cost of the Mg chemicals, the reduction in the overall struvite generation cost in the presented method is considerable. However, the NF separation method includes inherent potential disadvantages: along with Mg(II), other ions are also separated from the seawater (although with lower rejection values) e.g. Cl(-I) and Na(I), which contribute to the salinity of the wastewater effluents, and Ca(II) that may promote precipitation of unwanted calcium-phosphate solids, rendering the obtained struvite product less homogeneous thus less valuable. Consequently, the work focused on determining the best operational alternatives to attain the purest struvite product possible, using a fluidized bed (FB) reactor. The results show the approach to be highly feasible. A theoretical simulation was first carried out to determine the best operational conditions (pH, Mg(II) dosage through NF brine) to attain 90% P removal from the actual supernatant of a domestic-sludge dewatering facility. Total ammonia and orthophosphate supernatant concentrations were adjusted to simulate high (∼300 mg P/L and 600 mg N/L) and low (100 mg P/L and 450 mg N/L) nutrient supernatant concentrations. The FB reactor was fed with a mixture of supernatant and NF brine solutions, while pH was maintained constant via NaOH addition, and the hydraulic retention time was tested at 20, 30 and 60 min. In the six scenarios tested, P removal was higher than 90% and the struvite purity obtained was very high (∼95%), as demonstrated by both dissolution experiments and XRD analyses. The struvite precipitation experiments were carried out in the presence of an antiscalant agent, which was added to the NF brine to prevent the clogging of the NF membrane which was operated at 90% recovery to attain a concentrated Mg(II) brine.

AB - The paper describes the application of an alternative method for generating struvite (MgNH4PO4) solids from wastewater, using a low-cost Mg(II) solution, previously separated from seawater by nanofiltration (NF). Mg2+ ions are present at high concentrations in the oceans (∼1400 mg/L) and are well rejected by nanofiltration membranes, therefore, NF enables obtaining a concentrate that is rich in Mg(II) at a low cost. Since the largest cost component in conventional methods for struvite precipitation from wastewaters stems from the cost of the Mg chemicals, the reduction in the overall struvite generation cost in the presented method is considerable. However, the NF separation method includes inherent potential disadvantages: along with Mg(II), other ions are also separated from the seawater (although with lower rejection values) e.g. Cl(-I) and Na(I), which contribute to the salinity of the wastewater effluents, and Ca(II) that may promote precipitation of unwanted calcium-phosphate solids, rendering the obtained struvite product less homogeneous thus less valuable. Consequently, the work focused on determining the best operational alternatives to attain the purest struvite product possible, using a fluidized bed (FB) reactor. The results show the approach to be highly feasible. A theoretical simulation was first carried out to determine the best operational conditions (pH, Mg(II) dosage through NF brine) to attain 90% P removal from the actual supernatant of a domestic-sludge dewatering facility. Total ammonia and orthophosphate supernatant concentrations were adjusted to simulate high (∼300 mg P/L and 600 mg N/L) and low (100 mg P/L and 450 mg N/L) nutrient supernatant concentrations. The FB reactor was fed with a mixture of supernatant and NF brine solutions, while pH was maintained constant via NaOH addition, and the hydraulic retention time was tested at 20, 30 and 60 min. In the six scenarios tested, P removal was higher than 90% and the struvite purity obtained was very high (∼95%), as demonstrated by both dissolution experiments and XRD analyses. The struvite precipitation experiments were carried out in the presence of an antiscalant agent, which was added to the NF brine to prevent the clogging of the NF membrane which was operated at 90% recovery to attain a concentrated Mg(II) brine.

KW - Municipal wastewater

KW - Nanofiltration

KW - PHREEQC simulation

KW - Phosphate removal

KW - Struvite precipitation

UR - http://www.scopus.com/inward/record.url?scp=84874819530&partnerID=8YFLogxK

U2 - 10.1016/j.seppur.2013.02.002

DO - 10.1016/j.seppur.2013.02.002

M3 - 文章

AN - SCOPUS:84874819530

VL - 108

SP - 103

EP - 110

JO - Separation and Purification Technology

JF - Separation and Purification Technology

SN - 1383-5866

ER -