Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 23 MODIDICATION OF LEACHET CHARACTERISTCS IN LANDFILL USING MIXXTURE OF LIME AND SAWDUST WASTE Prof.Dr. Dheyaa Wajid Abud. Dr. Mohammed Ibrahem Basheer Al-Ubaidy Yousef A. Jassim dr.dheyaa@googlemail.com mohibrbas1@yahoo.com joe.iraq89@gmail.com Environmental Engineering DEP, Collage of Engineering, Al-Mustansiriya University. Received 28 June 2015 Accepted 23 November 2015 ABSTRACT Landfill bioreactor is a modified technique comparing with the conventional landfill processes due to its ability to reduce time for decomposition and enhancing the biogas generation. The basic goal of this paper is to investigate the performance of a three lab-scale bioreactors under anaerobic conditions. Three types of reactors differ in its internal composition were experimented ,bentonite clay was used as a cover material. First reactor was filled with organic solid waste only; second reactor was filled with a mixture of organic solid waste, Lime and sawdust, while the third reactor was filled with mixture of solid waste and lime. Leachate characteristics traced includes pH, EC, TDS, TSS, Heavy metals (Cr, Fe, Mn, Zn, and Mo), Sulfate SO -2 4 and Phosphate PO -3 4. Experiments were conducted from October 2014 to march 2015, Results shows a significant variation in removal efficiency for each reactor, heavy metals removal for the first reactor was (Mn 58.6%, Cr 13.4%, Mo 0%, Zn 27.2%, Fe 58.6%),and the second reactor removal efficiency was (Mn 77.2%, Cr 67.5%, Mo 69.19%, Zn 67.9%, Fe 56.7%), while for the third reactor was (Mn 30.1%, Cr 13.8%, Mo 18.48%, Zn 29.8%, Fe 70%). The results show that the solid waste, Lime and sawdust enhanced the removal of heavy metals in the 2 nd reactor which gave best removal efficiency for heavy metals. While the lime addition in the 3 rd reactor increase the removal efficiency of iron to 70%. It can be conclude that this modified landfill bioreactor enhance leachate characteristics and so enhancing the solid waste stabilization. KEYWORDS: Leachate, Landfill, Bioreactor, Lime, Sawdust, Anaerobic. الخشب نشارةو نفايات الجير من خليط باستخدام النفايات مكب عصارة خواص تعديل جيد جاسمأ.م.د ضياء واجد عبود م.د. محمد ابراهيم بشير العبيدي يوسف عبد الم Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 24 ة .الخالص الوقت تقليل على لقدرته نظرا التقليدية النفايات طمر عمليات مع مقارنةمعدل لعملية الطمر الصحي أسلوب هو حيويال مفاعلال حيوية مفاعالت ثالثة أداء في للتحقيق هو الورقة هذه من األساسي الهدف. الحيوي الغاز توليد تعزيز وكذلك لتحللالمطلوب لعمليات ا البنتونيت طين استخدامو لجميعها فقد تم الداخلي تكوينها ، تختلف هذه المفاعالت الحيوية الثالثة فيالالهوائية الظروف تحت مختلفة العضوية الصلبة النفايات من خليط معتم تشغيله الثاني المفاعل فقط، العضوية الصلبة النفايات مع األول المفاعل شغل. غطاء كمادة التي تم تتبعها العصارة خصائص. والجير الصلبة النفايات من خليط مع الثالث المفاعل تم تشغيل حين في الخشب، ونشارة والجير (، Cr, Fe, Mn, Zn, Moة، التوصيلية الكهربائية، المواد الذائبة الكلية، المواد العالقة الكلية، المعادن الثقيلة )الحموض درجةشملت SOالكبريتات ) -2 PO(، و الفوسفات ) 4 -3 4.) من المفاعالت مفاعل لكل اإلزالة كفاءة في كبير تفاوتاطهرت النتائج ،4102 مارس إلى 4102 أكتوبر منللفترة التجارب أجريت اما ,(Mn 58.6%, Cr 13.4%, Mo 0%, Zn 27.2%, Fe 58.6%) األول مفاعللل الثقيلة المعادن إزالةكفاءة كانت ،الثالث لمفاعلكفاءة االزالة في ا أن حين في ، ,(Mn 77.2%, Cr 67.5%, Mo 69.19%, Zn 67.9%, Fe 56.7%)المفاعل الثاني الصلبة، النفاياتمزيج أن النتائج أظهرت. .(Mn 30.1%, Cr 13.8%, Mo 18.48%, Zn 29.8%, Fe 70%) كان الثالث الثالث ادى الى زيادة المفاعل فيفقط الجير إضافة أن حين في. الثقيلة المعادن إزالة في المفاعل الثاني عززت الخشب ونشارة والجير من خالل نتائج البحث التوصل الى استنتاج الى ان التعديالت المقترحة للتركيبة الداخلية للمفاعالت يمكن٪. 01 إلى الحديد إزالة كفاءة .الصلبة النفايات تثبيت تعزيز و بالتلي العصارة خصائص تعزيز في افعاليته قيد البحث حسنت Nomenclature. EC: Electrical Conductivity. pH: Potential Hydrogen. TDS: Total Dissolved Solids. TSS: Total Suspended Solids. 1. INTRODUCTION. The landfill is the most common method for solid waste disposal and it is like other methods of treatment have advantages and disadvantages. Uncontrolled leachate and gas production are the major disadvantages as well as the public and aesthetic problems resulted from open dump solid waste disposal (Chart, 2004). Many researches were done in order to minimize the problems associated with landfill practices (Yuen, 2001). In order to improve knowledge of landfill behavior and decomposition processes of MSW, there has been a strong interest in upgrade existing landfill technology from a storage/containment concept to a process-based approach, in other words as a bioreactor landfill (Mostafa, 2002). Bioreactor is any system boosts the biological activity in a specific environment, and so bioreactor landfill is the technique that employs modification on the process of the conventional landfill either by leachate recirculation into MSW fills with or without oxygen supply or with chemicals to enhance the biological processes and reduce stabilization time needed for organic waste. The waste is considered stabilized when leachate is no longer pollution hazard, gas production and settlement is negligible (Borglin, 2004). The use of bioreactor landfill will significantly increase the organic solid waste decomposition over the ordinary organic solid waste landfill (Swati, 2007). The anaerobic digestion process takes place in an airtight container, known as a digester. The first stage of anaerobic digestion is a chemical reaction called hydrolysis (Shefali, 2002), where complex organics particles are separated into basic sugars, amino acids, and fatty acids with the addition of hydroxyl groups. This is followed by three biological processes: Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 25  Acidogenesis - further broken down by acidogenic bacteria into simpler molecules, volatile fatty acids (VFAs) occurs, producing ammonia, CO2 and hydrogen sulfide as byproducts.  Acetogenesis - the molecules particles from acidogenesis are further processed by microscopic organisms called acetogens to create CO2, Hydrogen and acetic acid (Ljupka, 2010).  Methanogenesis - methane, CO2 and water are produced by bacteria called methanogens. in order to maximize digestion, pH level should be kept within (5.5-8.5) and the temperature between 30- 60°C, in order to maximize digestion rates (Amin, 2012). In this paper a lab-scale solid waste bioreactor landfill will be used. Modification of the landfill bioreactor will be done by mixing waste with specific materials to improve the performance of solid waste stabilization and enhancing the leachate characteristics. 2. MATERIAL AND METHODOLOGY. Three lab-scales of bioreactors (Fig 1) have been designed and constructed in Al-Mustansiriya University, College of Engineering. 2.1. Structure and filling of reactors. 2.1.1. First reactor. First reactor made of ductile iron pipe of (1.3m) height and (0.4m) diameter, the effective height of solid waste was (1m). The reactor was underlying by (15cm) gravel layer for drainage purposes and PVC pipe for leachate collection as in fig (2). The solid waste in reactor was separated by a strainer from the gravel layer. the reactor was sealed by (15cm) bentonite clay as cover material, Bentonite are excellent sealants and absorbents, so it acts as an excellent barriers for landfills and toxic waste repositories (Haydn, 2002). Table (1) and (2) shows the chemical and physical characteristics of bentonite. The reactor was well lidded from top to ensure that the anaerobic conditions will occur. The reactor filled with (84kg) of dry and well compacted organic solid waste (corrupted fruits and vegetables), The waste density was 668.45kg/m 3 , The compaction was applied in order to increase the dry density which significantly speed up the degradation processes (Chart, 2004). 2.1.2 . Second and third reactor. The frame structure of the second and third reactors is identical, it made of ductile iron pipe, height and diameter are (1.1m) and (0.3m) respectively, The reactors were underlying by (15cm) of gravel layer and sealed from top by (15cm) bentonite. The solid waste effective height was (80cm) with drainage pipe for leachate collection as in figure (3). Second reactor was filled with (50kg) organic solid waste, 3kg of sawdust and 2.211 kg of Lime. The purpose of adding the saw dust is to reduce the volume of organic compound in the reactor as well as to investigate its behavior as adsorbent media. Lime was added in the 2 nd and 3 rd reactor to minimize the acidic affect on microorganisms activities, Lime proven a good capability in pH adjusting (Abdullahi, 2012), As well as the Lime will reduce the emission of Co2 and mitigate the greenhouse gases according to equation (1) (Guang, 2000). The third reactor was filled with (50kg) organic solid waste and (4.422 kg) of lime to find out the effect of sawdust absence. Table (3) describes the specification and filling mixture of the three reactors. Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 26 (1) 2.2. Monitoring of bioreactor landfill. The produced leachate was analyzed for parameters of pH, Sulphate SO -2 4 , Phosphate PO -3 4, EC, Fe +2 , Zn +2 , Cr +3 , Mn +2 , Mo +2 , Total Dissolved Solids TDS and Total Suspended Solid TSS. Standard Methods for wastewater examination (Eaton, 2005) and Spectrophotometers (HACH) were used. 3. RESULTS AND DISCUSSION. 3.1. The effect of lime on pH. The initial pH values differ in each reactor due to the Lime addition and its effects on pH value during the study period. Table (4, 5 and 6) describes the physiochemical characteristics of leachate generated through the study period from the 1 st , 2 nd and 3 rd reactors, respectively. The first reactor has initial pH of 4.9 and then increase slightly to 6.3 after 6 months of operation due to acid formation phase. pH value in 1 st reactor kept under pH value 6.4 which is the minimum optimum value for the anaerobic digestion (Fabien, 2003). While the pH initial value in 2 nd reactor was 6.07 and increased to 7.02 in two months due to the addition of 2.211 kg of Lime. In 3 rd reactor the initial pH was 7.1 due to the addition of 4.422 kg lime. Lime is considered as a pH regulator due to its effect in breaking down the organic matters and neutralizes acidity (Edson, 2011). 3.2. Removal of heavy metals. Initial leachate characteristics clearly showing that the leachate exhibited significant value of heavy metals such as Mo +2 , Fe +2 and Mn +2 . and the higher values of that three elements was in the 2 nd reactor which are 600mg/l, 277.7mg/l and 237.7mg/l for Mo +2 ,Fe +2 and Mn +2 respectively. In this study, Fe +2 values have been significantly reduced throughout the study period as shown in figure (4). The final effluent concentration of Fe +2 was varies among the three reactors, with 85mg/l, 120mg/l and 70 mg/l for the 1 st , 2 nd and 3 rd reactor, respectively. The optimum removal of Fe +2 was in 3 rd reactor with 70%. The highest removal was 70% for 3 rd and lowest removal for the 2 nd reactor which is very close to the removal of 1 st reactor which are 56.7% and 58.8%, respectively. The 4.422kg of Lime addition in the 3 rd reactor makes pH in range of (7.1-9.2) which increase the removal of iron as shown in figure (4), it’s observed that the increase in metals removal is related to the increase in pH (Hamidi, 2004), such result is due to the fact that most metallic elements are soluble in an acidic environment. 2 nd reactor leachate have the highest initial value for Mn +2 and Mo +2 , with 258.9mg/l and 600.3mg/l respectively, The final effluent was significantly reduced to 65mg/l and 185 mg/l for Mn +2 and Mo +2 , respectively with pH was in range of (6.07-8.8) as shown in figure (5). 2 nd reactor was more efficient in removal of Mn +2 and Mo +2 from leachate. The removal efficiency of Mn +2 and Mo +2 in 2 nd reactor was 77.2% and 69.19 %, respectively, While the removal efficiency in 1 st and 3 rd reactor was 23% Mn +2 , 0% Mo +2 and 30.1% Mn +2 , 18.48% Mo +2 , respectively. Sawdust is a more suitable adsorbent compared to rice husk in the removal of heavy metals from the simulated landfill leachate (Agbugui, 2015). Sawdust was capable of adsorbing Mn +2 and Mo +2 , Normally Mo +2 is anion forming metalloid and therefore like chromate, arsenic, uranium and vanadium, should be adsorbed best with pH value between (5-7) (Chistensen, 2010). Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 27 The polymeric material in sawdust is lignin, tannins or other phenolic compounds. From the nature of the material that are efficient in capturing heavy metal ions especially Cr +3 (Agbugui, 2015). In this study the initial values of Cr +3 and Zn +2 in 2 nd reactor was 9.4mg/l and 19.3 mg/l, respectively, which is higher than other reactors. The removal efficiency of both metals in the 2 nd reactor was 67.5% and 67.9%, respectively, as shown in the figure (6) which is the best removal among the other reactors throughout the study period. 3.3. Removal of SO -2 4 and PO -3 4. The initial value of SO4 in 2 nd reactor was 1206.7 mg/l which is the highest while the initial value of SO -2 4 for the 1 st and 2 nd was 262.4mg/l and 343.3 mg/l, respectively. The SO -2 4 reduced significantly to 253.2 mg/l in 2 nd reactor as shown in figure (7), While the effluent value from 1 st and 3 rd reactors was 200 mg/l and 130 mg/l. The removal efficiency of SO -2 4 in the 2 nd reactor was 79%. The initial value of PO -3 4 in 3 rd reactor was 24.9 mg/l and the effluent was 15.2 mg/l. the 3 rd reactor removed the PO -3 4 efficiently with a removal efficiency of 64.3% as shown in figure (8). The decline in phosphate concentration may due to the phosphate assimilation by microorganisms. 3.4. Removal of TSS. The TSS initial value in the 2 nd was higher than other reactors with 365 mg/l which decreased to 231mg/l in the first three weeks, then tend to increase to 470 mg/l, The final effluent throughout this study was 58 mg/l. the removal efficiency in the 2 nd and 3 rd reactors was 84.11% and 84.5% which indicates that both reactor have same behavior in removing TSS. Figures (9), (10) and (11) shows TSS concentration variation with time in 1 st ,2 nd and 3 rd reactors respectively, the fluctuation in TSS values appear in the previous figures may related to the variation of microorganism activity in breaking down organic matters, which effected by many factors such as pH and temperature. 4. CONCLUSION. Based on the previous results in the present study, it can be concluded the following: 1- Removal of heavy metals, phosphate and sulphate can be influenced significantly by mixture composition of solid waste in bioreactor landfill. 2- 1 st reactor which was containing solid waste only like an ordinary landfill was suffering from insignificance leachate enhancement. 3- Designed solid waste mixture in 2 nd reactor provided adsorbent media (sawdust) and pH adjustment material (lime), and such designed mixture enhanced the removal efficiency of heavy metals and sulphate. 4- 3 rd reactor although it was less efficient in pollutant removal than 2 nd reactor, however this reactor was more efficient in pollutant removal than 1 st reactor and such result prove the positive effect of lime addition as a pH regulator for microorganism activity. 5- The results showed that the 2 nd reactor have optimum removal for heavy metals and Sulphate, which makes the 2 nd reactor best choice among the other two reactors. Fe +2 was removed more efficiently by 3 rd reactor. Both 2 nd and 3 rd reactors were efficiently removed TSS from leachate. Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 28 A recommendation for future studies is the investigation the influence of leachate recirculation percent and ratios of sawdust and lime on the performance of reactors. 5. REFERENCES. [1] Abdullahi, M. Evuti, Aloko D. Folorunsho, Baba G. Agaie and Mohammed Jibril. “Predictive Model For Lime Dosage In Water Treatment Plant” International Journal of Scientific and Research Publications, Volume 2, Issue 12, December (2012). [2] Agbugui PA. and Nwaedozie JM. “Adsorption of Heavy Metals from Simulated Landfill Leachates unto Composite Mix of Agricultural Solid Wastes” IOSR Journal of Applied Chemistry (IOSR-JAC), Volume 8, Issue 2 Ver. I. Feb (2015), PP 49-54. [3] Amin M, Hamidi A, Nastaein Q. Zaman and Shuokr Q Aziz, " A Review on Anaerobic Digestion, Bio-reactor and Nitrogen Removal from Wastewater and Landfill Leachate by Bio- reactor” Advances in Environmental Biology, 6(7): 2143-2150, (2012). [4] Borglin, S. E., Hazen, T. C., Oldenburg, C. M., Zawislanski P. T. “Comparison of Aerobic and Anaerobic Biotreatment of Municipal Solid Waste” Technical Paper. J. Air & Waste Manage. Assoc. 54:815–822. (2004). [5] Chart Chiemchaisri, Wilai Chiemchaisri, C. Visvanathan, Josef Tränkler . “Bioreactor Landfill for Sustainable Solid Waste Landfill Management” report published by Faculty of Engineering Kasetsart University, 50 Phaholyotin Road,Chatuchak Bangkok 10900, Thailand, (2004). [6] Chistensen T.C, Michael Vendrp and Sofie Van Eemen “Removing SB, MO, SE, U, And BA from Wastewater and Leachate” 2 nd International Conference on Hazardous and Industrial Waste Management, Några Intressant föredrag Kreta 5-8 October (2010). 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Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 29 [10] Hamidi Abdul Aziz, Mohd Suffian Yusoff, Mohd Nordin Adlan,, Nurul Hidayah Adnan, Salina Alias “Physico-chemical removal of iron from semi-aerobic landfill leachate by limestone filter” Waste Management, Volume 24, Issue 4, (2004), pp 353–358. [11] Haydn Murray “Industrial Clays Case Study”, report was commissioned by the MMSD project of IIED, No 46, (2002). [12] Ljupka Arsova, “Anaerobic digestion of food waste: Current status, problems and an alternative product”, thesis submitted to Department of Earth & Environmental Engineering, Columbia University, may (2010). [13] Mostafa Warith “Bioreactor landfills: experimental and field results” Waste Management, Volume 22, Issue 1, (2002), pp 7–17. [14] Shefali Verma, “ANAEROBIC DIGESTION OF BIODEGRADABLE ORGANICS IN MUNICIPAL SOLID WASTES”, thesis submitted to Department of Earth & Environmental Engineering, Columbia University, May (2002). [15] Swati M., Obuli P. Karthikeyan, Kurian Joseph, and Nagendran R.,“ Landfill bioreactor – a biotechnological solution for waste management”, Journal of Scientific and Industrial Research, Vol. 66, No. 8, (2007), pp. 589-674. [16] Yuen S T S ”Bioreactor Landfills – Do They Work? “ Geoenvironment 2001: 2nd ANZ Conf on Environmental Geotechnics (Newcastle, Australia) 28-30 November (2001). http://people.eng.unimelb.edu.au/stsy/others/papers/geoenvironment2001_sy.pdf. Table (1): Chemical Composition of Bentonite Comp. SiO2 Al2O3 Fe2O3 CaO MgO Na2O Percentage 56.77 15.67 5.12 4.48 3.42 1.11 Comp. K2O P2O SO2 CL LiO3 Percentage 0.6 0.65 0.59 0.57 9.49 Table (2): Physical Properties Bentonite. Clay Type Surface area (m 2 /g) Density (Kg/m 3 ) Oil Retention (%) pH Adsorption of water vapor % Bentonite 220 750 35 10.1 11.8 Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 30 Table (3): specification and filling waste mixture of the three reactors. Reactor No. Components 1 2 3 Organic waste weight(kg) 84 50 50 Lime - 2.211 4.422 Sawdust (kg) - 3 - Density of mixture ( kg/m 3 ) 668 770 820 Cover material bentonite bentonite bentonite Table (4): characteristic of leachate from 1 st reactor. Item Time, Weeks 1 4 9 10 27 29 30 34 pH 4.94 5.22 6.06 6.26 6.3 7.46 6.05 6.22 Mn +2 mg/l 56.93 49.23 97.2 95.33 115.2 51.7 62.56 43.68 Zn +2 mg/l 4.715 3.67 7.98 9.44 9.27 4.29 4.78 3.43 SO -2 4 mg/l 262.44 195.9 456 346.6 486 209 220.8 200 PO -3 4 mg/l 22.7 38.4 35.4 33 23.04 11.33 15.08 9.36 TSS mg/l 279 400 350 621 314 241.9 309.5 600 Mo +2 mg/l 112.5 95.031 192 173.3 350 310 224.48 145.6 Cr +3 mg/l 2.11 1.61 3.27 4.33 3.335 2.3343 2.8 1.83 Fe +2 mg/l 205.4 306.9 249.6 330 191.7 90.68 110.77 85 Ec μS/cm 2006 3665 16004 17505 29983 31075 32678 18660 TDS ppm 1059 1920 8241 9014 15532 16115 17112 9325 Table (5): characteristic of leachate from 2 nd reactor. Item Time, Weeks 1 4 9 10 27 29 30 34 pH 6.07 6.4 6.72 7.02 7.5 8 8.3 8.8 Mn +2 mg/l 285.09 119.7 62.8 80.6 55.3 82.5 82.8 65 Zn +2 mg/l 19.3 7.29 5.36 7.06 4.69 6.38 7.56 6.2 SO -2 4 mg/l 1206 423 290.18 346.6 224 341 306 253.2 PO -3 4 mg/l 25.1 19.4 8.4 29.6 12.11 16.28 19.98 15.2 TSS mg/l 365 231 360 470 347.9 388 86.7 58 Mo +2 mg/l 600.3 451 401 321 250 310.2 257.4 185 Cr +3 mg/l 9.457 3.798 2.083 2.903 3.55 3.784 3.834 3.07 Fe +2 mg/l 277.7 181.2 238.2 280.8 90.1 140.75 140.94 120 Ec μS/cm 3249 3860 27859.5 28862.5 44010 37235 46890 19335 TDS ppm 1691 2009 14500 15022 22512 19173 23400 9660 Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 31 Table (6): characteristics of leachate from 3 rd reactor. Figure (1): 1 st , 2 nd and 3 rd reactors. Item Time, Weeks 1 4 9 10 27 29 30 34 pH 7.1 7.5 7.8 8 8.2 8.31 8.8 9.2 Mn +2 mg/l 70.09 114.24 79.4 95.33 70 72.75 53.2 49 Zn +2 mg/l 5.41 8.26 6.41 7.8 3.99 4.8 3.5 3.8 SO -2 4 mg/l 343.37 443.64 322.42 346.6 308 292.5 196 130 PO -3 4 mg/l 24.9 31.6 10.6 33 11.2 12.3 9.94 8.9 T.S.S mg/l 292 394 416 472 200 147.27 75.94 45.04 Mo +2 mg/l 330 205.2 160 200 301 270 277.2 269 Cr +3 mg/l 2.76 4.87 2.87 4.33 3.225 3.187 2.506 2.38 Fe +2 mg/l 237.7 301.8 282.7 330 110.9 122.25 90.94 70 Ec μS/cm 2628 4750 18933 23791.8 42254 34497 36540 24434.8 TDS ppm 1371 2500 9965 12522 21613 17955 18214 12213.8 Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 32 Figure (2): Scheme of 1 st bioreactor. Figure (3): Scheme of 2 nd and 3 rd reactors. Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 33 Figure (4): Variation of Fe +2 with pH increasing, 3 rd reactor. Figure (5): Variation of Mo +2 and Mn +2 with pH, 2 nd reactor Figure (6): Zn +2 and Cr +3 removal efficiency, 2 nd reactor y = 75265e-0.754x R² = 0.7006 0 50 100 150 200 250 300 350 400 7 7.5 8 8.5 9 9.5 10 F e + 2 m g /l pH y = 60.997x2 - 953.32x + 3766.4 R² = 0.7123 y = 55.656x2 - 950.37x + 4280.6 R² = 0.9032 0 100 200 300 400 500 600 700 6 6.5 7 7.5 8 8.5 9 C o n c e n tr a ti o n m g /l pH Mn Mo 0 10 20 30 40 50 60 70 80 90 0 5 10 15 20 25 30 35 % R e m o v a l Time, Weeks Zn Cr Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 34 Figure (7): variation with time, 3 rd reactor Figure (8): PO -3 4 variation with time, 2 nd reactor. Figure (9): TSS variation throughout time, 1 st reactor. y = 904.19x-0.374 R² = 0.7937 0 200 400 600 800 1000 1200 1400 0 5 10 15 20 25 30 35 40 S o 4 -2 , m g /l Time, Weeks y = 27.965e-0.033x R² = 0.6253 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 P O -3 4 , m g /l Time, Weeks 0 100 200 300 400 500 600 700 0 1 2 3 4 5 6 7 8 9 T S S , m g /l Time, Weeks Al-Qadisiyah Journal For Engineering Sciences, Vol. 9……No. 1 ….2016 35 Figure (10): TSS variation with time, 2 nd reactor. Figure (11): TSS variation throughout time in the, 3 rd reactor 0 50 100 150 200 250 300 350 400 450 500 0 1 2 3 4 5 6 7 8 9 T S S , m g /l Time, Weeks 0 50 100 150 200 250 300 350 400 450 500 0 1 2 3 4 5 6 7 8 9 T S S , m g /l Time, weeks