UserMicrosoft Word - revised JAEBS-1489-11J. Appl. Environ. Biol. Sci., 7(2)158-162, 2017 |
© 2017, TextRoad Publication |
ISSN: 2090-4274 |
Journal of Applied Environmental and Biological Sciences www.textroad.com |
Removal of Ammonium and Phosphate from Fertilizer Industry |
Wastewater Using Struvite Precipitation Method |
Nurani Ikhlas* and Warmadewanthi |
Department of Environmental Engineering, Faculty of Civil Engineering and Planning, |
Sepuluh NopemberInstitute of Technology (ITS) Surabaya, 60111, Indonesia |
Received: October 1, 2016 |
Accepted: December 24, 2016 |
ABSTRACT |
This research investigated the effect of pH and molar ratio [Mg2+]:[NH4+]:[PO43-]on struvite precipitation method for wastewater treatment from fertilizer industry. Struvite precipitation conducted in batch reactors, MgCl2 as precipitant and mechanically agitated for 158 rpm. Results show that pH optimum is pH 9 and molar ratio [Mg2+]:[NH4+]:[PO43-] optimum is molar ratio of 3:1:1 with removal efficiency of ammonium and phosphate reached 99%. |
KEYWORDS: ammonium, molar ratio, pH, phosphate, struvite |
INTRODUCTION |
Wastewater from fertilizer industry has contribution to water pollution because of high concentration of |
ammonium and phosphate.PT Petrokimia Gresik is one of fertilizer industry which has done to treat wastewater both in physic and chemical using precipitation method. This kind of treatment is not optimum because residual levels of phosphate and ammonia in wastewater treatment effluent exceeding quality standard effluent treatment [1]. High concentration of ammonium and phosphate was produced in wastewater treatment.The concentration of ammonium and phosphate from Production Unit I and III are 1724.61 mg/L and 3826.16 mg/L [1]. |
Struvite precipitation is white crystal consist of magnesium, ammonium, and phosphate in same molar concentration [2] and was used to supply Mgwhich act as an agent of precipitant.MgCl2 has been used because of good solubility and more effective precipitation process[3]. |
Another parameter that must be considered onstruvite precipitation are pH, molar ratio [Mg2+]:[NH4+]:[PO43-] [2]. Increasing the pH from 8 to 10 can increase 80-90%phosphate allowance. Research conducted by Anggrainy et al. [4]with a variation of pH 7, 8, and 9 for 150 minutes while stirring with a stirring speed of 100 rpm can be set aside phosphate reaches 91%.Another factor that can influence struvite precipitation is molar ratio of Mg2+: NH4+: PO43-[5]. Based on Pratama[1] researchoptimal precipitation occurs at a molar ratio [Mg 2+]: [NH4+]: [PO43-] 2: 1: 1.Total 30.74% and 99.75%ammonium phosphate can be excluded with a stirring speed of 200 rpm. |
MATERIALS AND METHODS |
Wastewater used in the research was mixed from wastewater treatment plant (Point L) and Production |
Unit III PT Petrokimia Gresik. Wastewater from Production Unit III as phosphate source mixed with wastewater from inlet of wastewater treatment plant (Point L) in order to get molar ratio [NH4+]:[PO4 |
The next step is prediction of pH variation, molar ratio [Mg2+]:[NH4+]:[PO43-]using Visual MINTEQ application (version 3.0). |
Table 1 Wastewater Treatment Characteristics |
Parameter | Method | Results |
pH | SNI 06-6989.11-2004 | 3.93 |
Magnesium | AAS | 422.40 mg/L |
Phosphate | Tin Chloride | 4263.83 mg/L |
Ammonium | Nessler | 859.38 mg/L |
Silicate | Molybdosilicate Method | 87.65 mg/L |
Calcium | Titrimetri EDTA | 576.00 mg/L |
Fluoride | SPADNS | 1.28 mg/L |
Turbidity | Turbidity meter | 59.70 NTU |
Table 1 shows that the results of mixed wastewater obtained concentration of phosphate and ammonium |
were 4263.83 mg/L and 859.38 mg/L with molar ratio [NH4+]:[PO43-] 1:1.06. Molar ratio [Mg2+]: [NH4+]:[PO43-] |
*Corresponding author: Nurani Ikhlas, Department of Environmental Engineering, Faculty of Civil Engineering and |
Planning, Sepuluh Nopember Institute of Technology, Surabaya, 60111, Indonesia. Email: nurani.ikhlas@gmail.com |
Ikhlas and Warmadewanthi, 2017 |
and pH prediction used Visual MINTEQ (version 3.0) application (US Environmental Protection Agency). |
Variation of pH values between 7 to 10 with increase pH 0.5. Data was entered in Visual MINTEQ and taken 3 variation values of optimum results as variable. Molar ratio was using 3 optimum results values from molar 3-] 1:1:1 to 5:1:1 and the amount increase molar Mg2+ was 1. Whereas for gradients |
agitated speed was determined from previous research Fitriana, 2016 [6] by using 158 rpm and agitating duration was 60 minutes to remove ammonium and phosphate from PTPetrokimia Gresik wastewater Production Unit II and III with struvite precipitation. |
Variation ofpH was chosen from pH optimum in the results of Visual MINTEQ application model. Adjustment of pH is done by adding crystals caustic soda or H2SO44N. This research varying magnesium in molar 3-] with magnesium based on ammonium and phosphate concentration based on |
ammonium existing in wastewater. Magnesium are coming fromMgCl2 and phosphate taken from wastewater in PT Petrokimia Gresik Production Unit III. Based on Fitriana, 2016[6] research, if magnesium ratio was increased, the amount of Mg2+which bonded with PO43-is also increased so phosphate removal ability will be higher. |
The main research consist of research implementation and parametersmeasurement. Explanation of each steps is as follows. |
a. Implementation of research |
Precipitation processes are using batch reactor. MgCl2 precipitant was added to 0.5 L wastewater according with the variation of molar ratio which has been set. The pH solution was adjusted to added crystals caustic soda or H2SO4 4N and homogenized. The solution was stirred by using jartest in 158 rpm for 60 minutes and allowed to stand for 30 minutes to sedimentation process. |
b. Measurement of parameters |
Parameters tested are ammonium pH, phosphate, Si2+, Ca2+, and F-. The measurement of pH was using pH meter, Ca2+ concentration using AAS instrument according to APHA standard method, 1980 [7], Si2+ concentration using Molybdosilicate method, whereas F- was using SPADNS method. The measurement of ammonium and phosphate was using Nessler method and Tin Chloride method. |
Precipitate analysis that has been conducted are composition analysis, morphology, and structure. Precipitate (struvite) composition analysis was conducted with the following steps. Precipitate was separated from supernatant with a filter by using Watman filter paper then was dried in room temperature for 48 hours [3] and be pondered until getting constant weight. The drying process was using oven because it would causes the structure of precipitate changed effect due to evaporation effect of ammonium bonds or hydrate[6]. Precipitate analysis was conducted by using SEM-EDX in Integrated Central Laboratory Diponegoro University Semarang. EDX analysis was usedfor determining the micro analysis elements forming precipitate. |
RESULTS AND DISCUSSION |
a. Results Prediction on pH and Molar Ratio [Mg2+]:[NH4+]:[PO43-] Variation |
Prediction of pH and molar ratio [Mg2+]:[NH4+]:[PO43-] variation was using Visual MINTEQ v3.0 application and determined by looking precipitate prediction. This prediction was conducted with entering pH value range 7-10 and ratio [Mg2+]:[NH4+]:[PO43-] with increase 0.5. Data input consist of magnesium concentration, ammonium, and phosphate according to molar ratio [Mg2+]:[NH4+]:[PO43-] in range 1:1:1- 5:1:1.Ions impurities concentration such as calcium, silicate, and fluoride was also added with wastewater. The results of precipitate prediction will be considered for determining variation that used in this research. |
Based on precipitate prediction, determination of pH variation in this research were pH 8, 9, and 10 because more struvite formed when pH 8 and 9 than pH 7 and 7.5. The determination of pH 10 was because the highest struvite content formed at pH 10. Basically in alkaline condition,precipitate were found in many forms such as brucite (Mg(OH)2), hydroxyapatite (Ca10(PO4)6(OH)2), chrysotile (Mg3(Si2O5)(OH)4), sepiolite (Mg4(Si6O15)(OH)4), and cristobalite. Precipitates could be formed because of Ca2+, Si2+, F-presence in wastewater existing that was included in modelling due to determine ions impurities effect on struvite formation. |
Precipitate prediction was used to determine variation in this research. Molar ratio [Mg2+]:[NH4+]:[PO43- |
] that has been selected were molar ratio 1:1:1, 2:1:1, and 3:1:1.Molar ratio 4:1:1 and 5:1:1 unselected because there were brucite and hydroxyapatite precipitate which can damage struvite structure and need more magnesium sources (MgCl2). |
b. Determination of pH and Molar Ratio Optimum on Struvite Precipitation |
MgCl2 addition as magnesium source for molar ratio [Mg2+]:[NH4+]:[PO43] 1:1:1, 2:1:1, and 3:1:1was used because it has highest solubility and more effective precipitation [3]. Acidity or pH was precipitation factor and an important role in struvite precipitate. The range pH for forming struvite was 6.5-10 [8]. |
J. Appl. Environ. Biol. Sci., 7(2)158-162, 2017 |
5000 | | | | 5000 |
| | | | |
4500 | | | | 4500 |
| | Residual ammonium experiment (mg/L) | | |
4000 | | Residual ammonium modelling (mg/L) | | 4000 |
3500 | | | | 3500 |
3000 | | | | 3000 |
2500 | | | | 2500 |
| | | | |
2000 | | | | 2000 |
1500 | | | | 1500 |
1000 | | | | 1000 |
500 | |
| | 500 |
0 | | | | 0 |
| | 8,0 8,5 9,0 9,5 | 10,0 | |
| | pH | | |
Residual phosphate experiment (mg/L) |
Residual phosphate modelling (mg/L) |
Figure 1: Effect of pH in Molar Ratio 1:1:1 |
5000 |
4500 |
4000 |
3500 |
Residual phosphate experiment (mg/L) |
Residual phosphate modelling (mg/L) Residual ammonium experiment (mg/L) Residual ammonium modelling (mg/L) |
5000 |
4500 |
4000 |
3500 |
3000 |
3000 |
2500 |
2500 |
2000 |
2000 |
1500 |
1500 |
1000 |
1000 |
500 500 |
0 0 |
8,0 8,5 9,0 9,5 10,0 |
pH |
Figure 2: Effect of pH in Molar Ratio 2:1:1 |
5000 |
4500 |
4000 |
3500 |
3000 |
2500 |
2000 |
1500 |
1000 |
500 |
0 |
Residual phosphate experiment (mg/L)
Residual phosphate modelling (mg/L) Residual ammonium experiment (mg/L) Residual ammonium modelling(mg/L) |
8,0 8,5 9,0 9,5 10,0 |
pH |
5000 |
4500 |
4000 |
3500 |
3000 |
2500 |
2000 |
1500 |
1000 |
500 |
0 |
Figure 3: Effect of pH in Molar Ratio 3:1:1 |
Ikhlas and Warmadewanthi, 2017 |
Figure 1 to 3 shows that pH can affect in decrease of phosphate concentration [9]. The results in pH 8 to |
9 was decreased phosphate concentration in molar ratio [Mg2+]:[NH4+]:[PO4 ]. The highest decreasing value of phosphate concentration in pH 9 was 4.26 mg/L from 4263.83 mg/L of initial concentration with 99.9% of removal efficiency. |
Kim et al., 2007 [10] research indicated the highest removal efficiency of phosphate in precipitate occurs to pH 9.The results shows that the highest efficiency in pH 9. However, pH 10 decreased phosphate concentration because decreasing of ions activity[3], furthermore there was another factors such as the presence of interfering ions decreasing phosphate removal. |
Effect ofpH against ammonium residual indicates that higher pH value, higher decreasing ammonium value. Figure 3 shows that pH 8 to pH 10 has ammonium residual 7.81 mg/L from initial concentration 859.375 mg/L with removal efficiency was 99.09%. That caused partial of ammonium have been volatilization. The higher pH value could move ammonium equilibrium to be ammonia aqueous (NH3(aq)) which was volatile [11]. |
Based on Figure 1, 2, and 3 indicated the influence of molar ratio variation [Mg2+]:[NH4+]:[PO43-] were ratio 1:1:1, 2:1:1, and 3:1:1. Molar ratio variation conducted by varying magnesium concentration which was MgCl2 addition. MgCl2act as magnesium sources. MgCl2requirementformolar ratio variation 1:1:1, 2:1:1, and 3:1:1 are 3.06 gram, 7.92 gram, and 12.77 gram. |
The results from phosphate and ammonium residual in pH9 as optimum pH with molar ratio |
3-] 1:1:1, 2:1:1, and 3:1:1 was compared with the result of modelling phosphate and ammonium removal to determined optimum molar ratio. Based on optimum pH condition (pH 9) occurred significant decrease with molar ratio [Mg2+]:[NH4+]:[PO4 |
percentage will increase [6]. This research shows that the highest percentage phosphate removal in pH 9 with molar ratio [Mg2+]:[NH4+]:[PO43-] 3:1:1 was 99.9% that indicated pH 9 as optimum pH and ratio 3:1:1 was optimum. Molar ratio Mg2+addition could increasing phosphate removal efficiency, its according from the results Warmadewanthi and Liu [3] that phosphate removal efficiency could increase along with increasing molar ratio. |
c. Struvite and Mineral Impurities Identification Using SEM-EDX |
Analysis Scanning Electron Microscope (SEM) was conducted to determine morphology characteristic and crystals structure. Energy Dispersive X-ray Spectroscopy (EDX) was conducted to determine the chemical components contained in crystals. Analysis were performed at the Integrated Central Laboratory of Diponegoro University in Semarang. SEM analysis performed with magnification of 2000x. |
According to Liu et al. [12] forms of struvite crystals can be prismatic, pyramid, needle, tapered, and irregular. Figure 4 shows SEM results from the control sample (ratio [Mg2+]: [NH4+]: [PO4 |
a pH of 9 elliptical-shaped crystals). |
Figure 4. Sampel Struvite Crystal in |
Figure 5. EDX Microanalys in |
Ratio[Mg2+]:[NH4+]:[PO43-] 3:1:1 |
Ratio[Mg2+ |
]:[NH4 |
+]:[PO43-] 3:1:1 |
Figure 4 and 5 shows that some ion impurities contained in precipitates: calcium, fluoride, Na, Cl, and |
silicate. Na ions can be foundin precipitates because caustic soda crystals in precipitates lead to pH value raise. While Cl ions from magnesium sources used in the form of MgCl2.Struvite crystals formed into a long round with a rough surface due impurity ions contained in the wastewater causes damage to struvitesurface. |
J. Appl. Environ. Biol. Sci., 7(2)158-162, 2017 |
CONCLUSION |
Result showsthat optimum pH is on pH 9 with 4.25 mg/L phosphate residual and 31.25 mg/L ammonium residual |
using MgCl2precipitant (magnesium sources). Molar ratio [Mg2+]:[NH4+]:[PO43-]optimum on ratio 3: 1: 1 with 99.9% of phosphate removal efficiency reached.Struvite precipitation in the sample molar ratio [Mg2+]:[NH4+]:[PO4 ]3: 1: 1 had a crystal form elliptical but had impurities that damage the surface of struvite. |
REFERENCES |
[1] Pratama, R.R.P. Recovery of ammonium and phosphate from PT Petrokimia Gresik wastewater using |
magnesium addition. Environmental Engineering. Surabaya.2015. 3-5 |
[2] Khai, N. M. and Hoang, T. Q. T. Chemical precipitation of ammonia and phosphate from Nam Son landfill leachate, Hanoi.Iranica Journal of Energy & Environment 3 (Special Issue on Environmental Technology). 2012. 3;32-36. |
[3] Warmadewanthi and Liu, J.C.. Recovery of phosphate and ammonium as struvite from semiconductor wastewater. Separation and Purification Technology.2009. 64;368- 373. |
[4] Anggrainy, A. D., Bagastyo, A. Y., and Hermana, Joni. Effect of pH and stirring speed crystallization process against low phosphate concentrate in wastewater. National ConferencesEnvironmental Engineering XI. 2014. 23-29. |
[5] Kumar, R. and Pal, P. Turning Hazardous Waste into Value Added Products: Production and Characteristization of Struvite Ammonical Waste with New Approaches. Journal of Cleaner Production. 2013. 43;14;59-70. |
[6] Fitriana, Rodliya. Removal of ammonium and phosphate from wastewater from production unit II and III of PT Petrokimia Gresik with precipitation struvite method. Environmental Engineering. Surabaya. 2016. 65-70 |
[7] APHA. Standards Methods for the Examination of water and wastewater. 20th ed. APHA, AWWA, WPCF, |
American Public Health Association. Washington DC. 1998. 543-587 |
[8] Bowers, K. E. Development of a Struvite crystallizer for reducing phosphorus in effluent from livestock waste lagoons. PhD. North Carolina State University. 2004. |
[9] Su’udi, Misbahul. Removal of phosphate from PT Petrokimia Gresik wastewater using gypsum waste. |
Environmental Engineering. Surabaya. 2015. 70-72 |
[10] Kim, D., Kim, J., Ryu, H.-D., and Lee, S.-I. Effect of mixing on spontaneous struvite precipitation from semiconductor wastewater. Journal of Bioresource Technology. 2007b. 100;74–78. |
[11] Chimenos, J. M., Fernandez, A. I., Hernandez, A., Haurie, L., Espiell, F., and Ayora, C. Optimization of phosphate removal in anodizing aluminium wastewater. Water Research.2006. 401;137–143 |
[12] Liu b., Giannis A., Zhang J., Chang V., and Wang JY. Characterization of induced Struvite formation from source-separated urine using seawater and brine as magnesium sources. Journal of Chemosphere. 2013. 93;2738-2747. |