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The Effect of Alum on Phosphorus Sequestration, Macrophytes, Mineralogy, and Microbial Activity in a Wastewater Treatmen

This study investigates the effectiveness of alum treatment in a wastewater treatment wetland and its impact on phosphorus sequestration, the growth of aquatic macrophytes, changes in mineralogy, and microbial activity. Various experiments, including laboratory studies, mesocosm experiments, and field studies, will be conducted to evaluate the effects of different alum dosages and alternatives.

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The Effect of Alum on Phosphorus Sequestration, Macrophytes, Mineralogy, and Microbial Activity in a Wastewater Treatmen

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  1. The Effect of Alum on Phosphorus Sequestration, Macrophytes, Mineralogy and Microbial Activity in a Wastewater Treatment Wetland Lynette Malecki IFAS, Soil and Water Science Dept. Wetlands Biogeochemistry Laboratory

  2. Iron Bridge WWTF St. Johns Rv. Orlando OEW OEW Facts • 1,200 acre wetland constructed in 1986 • 17 cells, 32 water control structures • Treats 35 mgd from Iron Bridge Wastewater Treatment Plant

  3. 17 13 7 14 3 8 16A 4 1 9 5 16B 2 10 6 11 15 12 410 ac. Deep marsh 380 ac. Mixed marsh 310 ac. Hardwood swamp Project Location Outflow 17 17 13 13 7 7 14 14 3 3 8 8 16A 16A 4 4 1 1 9 9 5 5 16B 16B 2 2 10 10 6 6 Inflow Inflow 11 11 15 15 12 12

  4. . . Outflow Outflow North North Central Central Inflow Inflow Permit limits: Permit limits: South South TP 0.2 mg/L TP 0.2 mg L-1 TN 2.31 mg/L TN 2.31 mg L-1 Flow Trains

  5. 0.6 Inflow TP Outflow TP 0.5 0.4 TP (mg L-1) 0.3 0.2 0.1 0.25 0.25 New permit Former SJRWMD threshold limit Former permit limit limit 0.0 0.20 0.20 New limit Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 TP (mg L-1) 1 1 0.15 0.15 - - mg TP L mg TP L 0.10 0.10 0.05 0.05 0.00 0.00 Jan Jan - - 98 98 Jan Jan - - 99 99 Jan Jan - - 00 00 Jan Jan - - 01 01 Jan Jan - - 02 02 Jan Jan - - 03 03 The Problem Concern over P binding capacity

  6. Management Strategies • Prescribed burning • Cell 1,3,8,9,10 • Dredging • Cell 1,3,4,7,8 • Chemical amendments

  7. Alum (Al2(SO4)3•14H2O) • pH of 2.4 • Dissociates in water forming Al3+ ions that are immediately hydrated: • Al3+ + H2O  Al(OH)2+ + H+ • Al(OH)2+ + H20  Al(OH)2+ + H+ • Al(OH)2+ + H20  Al(OH)3(s) + H+ • For P inactivation need system pH 6 to 8

  8. Alum Alternatives • PAC (Aln(OH)mCl(3n-m)) • Stronger highly charged polymers, faster settling flocs • pH buffer is not needed • 2.5 times more expensive • PNAS • Add powdered calcium carbonate to concentrated alum • 0.1 times more expensive • Alum residual • free from water treatment plants • heavy metal content • seed bank

  9. Aluminum Toxicity • Toxic to fish • Lose ability to maintain osmoregulatory balance and respiratory problems (Baker, 1982) • Toxic to benthos • Decreased benthic biodiversity and density, floc interferes with movement and feeding (Smeltzer, 1990 and 1999)

  10. Aluminum Toxicity • Toxic to plants • Disrupts structure and function of plasma membrane • Inhibits ATP and DNA synthesis • Inhibits root elongation • Results in P, Ca, and Mg deficiencies

  11. Case Studies • Mirror Lake, WI (Garisson and Knauer, 1984) • Urban storm drainage diverted in 1976 • Severe blue-green blooms and internal loading • 1978 alum applied (6.6 mg Al L-1) • Water column TP decrease 90 μg L-1 to 20 μg L-1 • Treatment lasted through 1991 (TP< 40 μg L-1 ) • Eau Galle Reservoir, WI (Barko et al., 1990) • High external and internal loading • 1986 Dose = 5 yrs * avg summer internal load • Effective for one summer • P inactivation ineffective when external loading remains high

  12. Case Studies • Wapato Lake, WA (Welch and Schrieve, 1994) • Residential and commercial storm water • High turbidity, algal blooms, dense Ceratophyllum • 1984 alum (7.8 g Al m-3) • TP reduced for one month • Increase in plant biomass and pH increased to 10.1 • TP increased 24% due to sediment P release and plant senescence

  13. Hypotheses • Alum will effectively sequester P in a municipal treatment wetland. • Alum will decrease the growth and nutrient uptake of aquatic macrophytes. • There will be a decline in biomass and activity of the microbial community. • Changes in mineralogy will be evident due to the alum application.

  14. Objectives I. Determine the effectiveness of: • Alum treatment in the OEW • Alum, alum residual, PAC, and PNAS

  15. Objectives II. Determine the effects of alum on: • Aquatic macrophytes • P cycling / microbial activity • Mineralogy • Water column and soil Al speciation

  16. Tri-Scale Experiment Laboratory and Core Incubation Studies Mesocosms Paired Cell Field Experiment

  17. Proposed Bioreactor Studies • Alum dosage variable, pH constant • pH variable, alum dosage constant 4 6 8 3 5 9 Patrick et al., 1973

  18. Proposed Core Study • Effectiveness of alum, alum residual, PAC, and PNAS vs. control • P flux into water column • Al speciation in water column • Effect on soil P fractions and Al fractions • Soil microbial characteristics • Change in water column and soil pH

  19. Proposed Mesocosm Study • Effect of alum on cattails, bulrush, and SAV • P flux into water column • Al speciation in water column • Effect on soil P fractions and Al fractions • Soil microbial characteristics • Change in water column and soil pH

  20. 9 5 10 6 Proposed Paired Cell Field Study • Alum treated vs. control cell • Monitor inflow and outflow TP, Al, and pH • Collect multiple intact cores (0, 3, 6, 9, 12, 18, 24 mo.) • Soil characterization • Al and P fractionation • Mineralogical composition analysis • Plant biomass and nutrient uptake

  21. Methods I. • Soil and water column pH • Total inorganic P (Reddy et al., 1998) • Total P, L.O.I. (Anderson, 1976) • Inorganic P fractionation (Psenner et al., 1984; Reddy et al., 1998) • Microbial biomass P (Ivanoff et al., 1998; Brookes et al., 1985) • Sediment Oxygen Demand (SOD) (Fisher and Reddy, 2001) • Potentially mineralizable P (PMP) (White and Reddy, 2000) • Al fractionation (Srinivasan and Viraraghavan, 2002; Bertsch, 1990) • Ammonium oxalate and citrate-dithionate Al extraction

  22. Methods II. • Plant productivity and biomass (Davis, 1984 ; Madsen, 1993) • TP, TN, Al, Ca, Mg plant tissue analysis (Allen et al., 1974; James et al., 1983) • Particle size fractionation and X-ray diffraction analysis • Thermogravimetric weight loss (Karathanasis and Harris, 1994) • Density separations and SEM

  23. Data Analysis • Kolmogorov-Smirnov normality test (α = 0.05) • Bartlett’s test for equal variance • ANOVA to determine differences in parameters with Tukey’s W multiple comparison procedure • Paired student t-tests (α = 0.05 ) between depth intervals • Pearson product-moment correlation coefficients (α = 0.05) between parameters • Regression analysis of necessary relationships

  24. Anticipated Results • Alum will work effectively in sequestering P in a treatment wetland, however will the longevity of the treatments effectiveness persist? • Will the microbial biomass and activity only be affected in the short term? • Will alum affect the macrophytes and mineralogy of the soil in both the short and long term?

  25. Research Implications • Usefulness of alum as a wetland management technique • Possible future use of PAC or PNAS in natural systems • Stimulate similar research in lake systems

  26. THANK YOU

  27. pH 1.0 (2 h) Total Al (Al ) T Suspended Al (Al ) ss (Al ) - (Al ) T (C+D) Filter, pH 1.0 (2 h) Colloidal and 50 mL DI (1 h) Dried dissolved Al (Al ) Ground Soil (C+D) Colloidal Al (Al ) C (Al ) - (Al ) (C+D) (I+O) Filter Filter Dissolved Al (Al ) (I+O) Cation Exchange Resin Inorganic Al (Al ) I (Al ) - (Al ) (I+O) O Organic Al (Al ) O Al Speciation Adapted from (Srinivasan and Viraraghvan, 2002; Yamada et al, 2002)

  28. Dose Determination Methods • Titrate water samples of different alkalinities with alum to a pH of 6.0 (Kennedy and Cooke, 1982) • Dose = 2(average summer internal P load * target period) (Kennedy et al., 1987) • Test different doses (1.4-21.8 g kg-1) on 5 g air-dried soil + 25 mL DDI shaken for 3 days and analyzed for SRP (Ann, 1995) • Determine the amount of mobile P (labile and Fe-P) in the upper 4-10 cm and multiply by 100:1 ratio of Al added: Al-P formed (Rydin and Welch, 1999)

  29. POP DOP SRP POP DOP SRP Phosphorus Cycle Inflow Outflow Ca/Mg/Fe/Al-P Recalcitrant P

  30. Soil 1 M KCl (2 hrs) Readilyavailable Pi Residue 0.1 M NaOH (17 hrs) 0.11M NaHCO3 / 0.11M Na2S2O4 (1 hr) Fe - bound PI Alkali extractable Po (TP-SRP) Al - bound Pi Residue 0.5 M HCl (24hrs) Residue Ca / Mg - bound Pi Residual P (Po) Inorganic P Fractionation Adapted from (Rydin ey al., 2000; Reddy, K. R. et al., 1998; Psenner et al., 1988; Psenner et al., 1984)

  31. Materials Average OEW Cell 10 soil characterization (0-4 cm): • 50-60% organic matter • Soil pH 5.0-6.0 • 10 g kg-1 Ca • 170 mg kg-1 Al/Fe-bound P Samples Used: • OEW1 = 812 g m-2 (14.4 ppm)powder alum • OEW2 = 406 g m-2 (7.2 ppm)powder alum • OEW3 = 406 g m-2 (7.2 ppm)liquid alum

  32. Methods • Samples were air dried, crushed with mortar and pestle. • Mini 270 sieve to separate sand from silt and clay • Side powder mounts of silt + clay fraction • Silt and clay separated via pH 10 water centrifugation • Side powder mounts of silt fraction • Clay tiles or quartz aluminum mounts of clay fraction

  33. XRD Silt + Clay Fraction

  34. OEW 1 Silt + Clay d=7.21

  35. XRD Silt Fraction

  36. XRD Clay Fraction

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