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The Effect of Alum on Phosphorus Sequestration, Macrophytes, Mineralogy and Microbial Activity in a Wastewater Treatment Wetland Lynette Malecki IFAS,

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Presentation on theme: "The Effect of Alum on Phosphorus Sequestration, Macrophytes, Mineralogy and Microbial Activity in a Wastewater Treatment Wetland Lynette Malecki IFAS,"— Presentation transcript:

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

3 A 16B Inflow A 16B A 16B Inflow Outflow 410 ac. Deep marsh 380 ac. Mixed marsh 310 ac. Hardwood swamp Project Location

4 Flow Trains

5 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 (Al 2 (SO 4 ) 314H 2 O) pH of 2.4 Dissociates in water forming Al 3+ ions that are immediately hydrated: – Al 3+ + H 2 O  Al(OH) 2+ + H + –Al(OH) 2+ + H 2 0  Al(OH) H + –Al(OH) H 2 0  Al(OH) 3 (s) + H + For P inactivation need system pH 6 to 8

8 Alum Alternatives PAC (Al n (OH) m Cl (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 Paired Cell Field Experiment Mesocosms

17 Proposed Bioreactor Studies Alum dosage variable, pH constant pH variable, alum dosage constant 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 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?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 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?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 techniqueUsefulness of alum as a wetland management technique Possible future use of PAC or PNAS in natural systemsPossible future use of PAC or PNAS in natural systems Stimulate similar research in lake systemsStimulate similar research in lake systems

26 THANK YOU

27 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 ( 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 Phosphorus Cycle POP DOP SRP Inflow Recalcitrant P Ca/Mg/Fe/Al-P POP DOP SRP Outflow

30 Inorganic P Fractionation Soil Residue 1 M KCl (2 hrs) Readily available P i Alkali extractable P o (TP-SRP) 0.1 M NaOH (17 hrs) Al - bound P i Ca / Mg - bound P i 0.5 M HCl (24hrs) Residual P (P o ) Residue Fe - bound P I 0.11M NaHCO 3 / 0.11M Na 2 S 2 O 4 (1 hr) 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 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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