PRESENTATION BY PRESENTATION BY PRESENTATION BY PRESENTATION BY :Munanura JAMES:Munanura JAMES:Munanura JAMES:Munanura JAMES....REG: NO: 2011/HD13/4234XREG: NO: 2011/HD13/4234XREG: NO: 2011/HD13/4234XREG: NO: 2011/HD13/4234XSTUDENT NO:STUDENT NO:STUDENT NO:STUDENT NO: 211017023211017023211017023211017023

April: 2013April: 2013April: 2013April: 2013

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� Operation of SSF constructed wetland inbatch mode (alternating drain and fill cycles)is a strategy that may improve both nitrogenand phosphorus removal efficiency inwastewater wetlands.Studies have shown that alternating periods� Studies have shown that alternating periodsof aerobic and anaerobic soil conditionscould facilitate the sequential coupling ofnitrification and denitrification, with nitrategenerated during the aerobic phase beingdenitrified in the anaerobic phase.

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� To evaluate the influence of batch versus continuous mode on the removal efficiencies of chemical oxygen demand (COD), N, and P in tropical SSF constructed wetlands.

� To evaluate the quantitative role of the higher� To evaluate the quantitative role of the higher

aquatic plants in nutrient removal in these two alternative operational modes.

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� Six beds of typical SSF CW were set.� The location is a typical tropical environment

and is generally hot and humid year round. The average temperature ranges from 23˚C to 32˚C (74 Fe86 F).Beds were filled with gravel.� Beds were filled with gravel.

� Three HSSF CWs were planted with cat-tail (Typha Angustifolia) at a density of approximately 14-15 plant/m2, and 3 beds without plant. The latter were used as “unplanted” control beds.

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� The operational modes included batch-loaded and continuously loaded systems.

� Two periods with identical conditions were used. (Batch: April – June 2010, Continuous mode: Sept. – Nov. 2010).mode: Sept. – Nov. 2010).

� Effluent samples were collected same day, time and every two and four days in 1l glass bottles.

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� PHYSICAL AND CHEMICAL PARAMETERS.

TABLE 1

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� Fig 3. shows the comparison of NH4-Neffluent concentrations between batch andcontinuous modes for the test series with 4-day retention time. In planted beds, statisticalanalysis showed that there was significantanalysis showed that there was significantenhancement (p < 0.001) of NH4-N removalin batch flow mode (95.2%) as compared tocontinuous flow operation (80.4%); while inunplanted beds, there was no significantdifference (p > 0.05) for batch flow (49.3%) ascompared to the continuous flow mode (47%)

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� Fig. 4 shows the comparison of the TPeffluent concentration between batch andcontinuous flow modes for the 4-dayhydraulic retention time. For both plantedand unplanted beds, there was significantand unplanted beds, there was significantenhancement (p < 0.05) in TP removal inbatch flow operation (69.6% for planted beds;39.1% for unplanted beds) as compared tocontinuous flow operation (46.8% for plantedbeds; 25.5% for unplanted beds).

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� COD removal was not significantly affected bythe presence of plants in the batch operatedwetlands.

� However, for the 4-day residence time in ourcontinuous flow wetlands, there was acontinuous flow wetlands, there was asignificant (p < 0.05) difference betweenplanted and unplanted beds, even though thedifference in removal efficiency for theplanted beds (95.9%) was only slightly betterthan that for the unplanted (91.1%).

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� The reasons for this are unclear, butapparently are reflective of the fact that atleast at the typical COD loading rates, thesum of the processes of aerobic (andanaerobic) organic carbon degradation actinganaerobic) organic carbon degradation actingsolely in a gravel filter (with no plants) aresufficient to drive BOD5/COD degradation tonear completion without the need for eitherplant rhizosphere aeration or drain and

fill operational.

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� Batch operation of SSF CWs has been proposed as amethod for enhancing movement of air into thegravel pore spaces, and thereby stimulating theoxidation of C and N and removal (adsorption) of P.

The results obtained from comparing batch versuscontinuous flow modes for a tropical SSF CW,continuous flow modes for a tropical SSF CW,showed that while these alternative loadingmethods had no significant effect on C oxidation(COD removal), both N oxidation and P removalwere significantly enhanced in the batch operationas opposed to continuous flow mode operated at 4day HRT.

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� The findings of this study imply that where maximal N and P removal is desired, periodic draining and filling might be the preferred operational strategy for a full-scale SSF constructed wetlandconstructed wetland

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� The results of this study on batch versuscontinuous flow modes of operation for atropical SSF CW showed that while theseloading methods had no significant effect onCOD removal, both ammonia oxidation andCOD removal, both ammonia oxidation andTP removal were significantly enhanced inbatch versus continuous mode.

� At a 4-day HRT, the presence of plantssignificantly enhanced both ammoniaoxidation and TP removal in both batch andcontinuous modes of operation as comparedto that for unplanted beds.

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� The findings of this study imply that where maximal N and P removal is desired, periodic draining and filling might be the preferred operational strategy for a full-scale SSF constructed wetland.constructed wetland.

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� MURAKOZE CYANE.

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