Phosphorus recovery from wastewaters through struvite formation | |
| Author | Patiya Kemacheevakul |
| Call Number | AIT Thesis no.EV-08-27 |
| Subject(s) | Phosphorus Phosphatic fertilizers |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | At present natural resources scarcity is a major problem in the world and phosphorus (P) is one of the important natural resources. P is used as fertilizers especially in agricultural countries. Nowadays, several research have focused on P recovery from wastewaters, and struvite formation is one of the effective ways to recover P from wastewaters in the form of crystals. However, this method has found limitations for full scale practical applications because chemicals for precipitation can be expensive and formation of struvite crystals may require certain environmental conditions. This study employed 3 kinds of wastewaters such as synthetic, piggery and urine, in P recovery through struvite formation. The synthetic wastewater was studied by varying pH from 9 to 13, ratios of NH₃-N: P and Mg: P of 0.5:1, 1:1, 5:1, 10:1, 20:1 and 30:1 at pH 9 and 0.5:1, 1:1, 5:1, 10:1, 30:1 and 50:1 at pH 11. The pH 11 gave the highest P concentration in precipitate of 80.25 mg/L. The minimum NH₃-N: P ratio for effective P recovery was 1:1 for the pH values 9 and 11, while the minimum Mg: P ratios for effective P recovery were 1:1 and 5:1 for the pH values 9 and 11, respectively. The piggery wastewater was studied by varying pH from 9 to 12. The highest P recovery was 38.91 mg/L at pH 9. The urine samples consisting of male and female's urine were studied by varying pH from 9 to 11. The highest P recoveries were 135.34 and 79.41mg/L at pH 11 in male and female's urine, respectively. The mineralogical structure and structure of precipitates, determined by X-ray diffraction analysis and scanning electron microscopy (SEM) at the National Metal and Materials Technology Center (MTEC) laboratory, Pathumthani province, Thailand, were found to be of struvite, syn-NH₄MgPO.6H₂O. The P solubility of struvite samples in soils with moisture contents of 15 and 50% at pH 9 were 47.60 and 63.06% of the original P contents which should be available for crops uptake. An integrated model to predict P recovery from struvite formation was developed which incorporated such important parameters as: pH, ratios of NH3-N: P and Mg: P. The model coefficients were determined from the experimental data by using SPSS 11.5 program with a satisfactory correlation coefficient value. Assuming 90% P recovery from urine wastewater through increased Mg: P ratio, the current cost to recover I kg P through struvite formation is about 222.22 Baht which is forth the current cost of chemical fertilizers. Due to increased demand of P and inflationary factors, the price of P is expected to increase in the near future and making the P struvite more attractive. |
| Year | 2008 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Chongrak Polprasert; |
| Examination Committee(s) | Preeda Pakpian;Thammarat Koottatep; |
| Scholarship Donor(s) | Thailand (HM Queen); |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2008 |