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A low-cost and efficient methodology was used to test the performance of a biofilter removing gaseous hydrogen sulfide generated in the headworks and a primary clarifier of a local Wastewater Treatment Plant. The contaminated gas stream is distributed upward through 1,718 m3 of filter material. With a flow rate varying between 3,503.0 m3/h and 4,587.3 m3/h and hydrogen sulfide inlet concentrations between 0.8 and 146 ppm, hydrogen sulfide was efficiently eliminated by the wood bark biofilter. The removal efficiencies ranged from 97.5% to 99.9%. The mean water content of the filter material was determined to be 67.1%. The excess water existing in the unit and long residence times may have provided the appropriate conditions for a high hydrogen sulfide removal.

Odour emissions resulting from reduced sulphur compounds in the kraft pulping industry are frequently found in dilute, high flowrate air streams that are costly to treat using incineration and thermal oxidation. Biofiltration, an air treatment method involving passing air through a packed bed of microorganisms, has emerged as a promising treatment strategy for these dilute waste gas streams. However, biodegradation of dimethyl sulphide (DMS) in biofilters is rather poor and is limiting the application of biofiltration to odour streams rich in DMS. Recently, our group has shown that co-treatment of DMS with methanol can increase DMS removal significantly. In this thesis, the effect of methanol on the microbiology of two biofilters treating DMS was explored. Microbial community analysis revealed that the addition of methanol led to a significant increase of up to an order of magnitude in the abundance of Hyphomicrobium spp. in a biofilter co-treating DMS and methanol compared to a biofilter treating DMS alone with no significant difference in the abundance of Thiobacillus spp. between the two biofilters. Further to the biofiltration experiments, the growth kinetics of Hyphomicrobium spp. and Thiobacillus spp. on DMS and methanol in an enrichment culture created from a biofilter co-treating DMS and methanol were studied. A specific growth rate of 0.099 h-1 and 0.11 h-1 was determined for Hyphomicrobium spp. and Thiobacillus spp., respectively, growing on DMS at pH 7, double the highest maximum specific growth rate for bacterial growth on DMS reported to date in the literature. As the pH decreased from pH 7 to pH 5, the specific growth rate of Hyphomicrobium spp. decreased significantly by 85% in the mixed culture while the specific growth rate of Thiobacillus spp. remained similar through the same pH shift. When methanol was used as a substrate, the specific growth rate of Hyphomicrobium spp. declined much less over the same pH range (up to 30%). These results suggest that addition of methanol to biofilters co-treating DMS and methanol can increase DMS removal rates by increasing the abundance of DMS-degrading Hyphomicrobium spp. at pH levels not conducive to high growth rates on DMS alone.

Recently, treatment plants have adopted biofiltration to compliment conventional treatment and ozonation. Previous literature has focused on passive applications of biofiltration. In this study, several pilot-scale biofiltration trains were designed in parallel to conventional treatment to investigate the impact of nutrient addition (nitrogen and phosphorus), use of hydrogen peroxide, aluminum sulphate (alum), and different filtration media (anthracite vs. granular activated carbon (GAC)) on biofiltration performance. Parameters measured included organic removal, reduction of DBP precursor, improvements in filter runtimes and ultrafiltration (UF) fouling control. Nutrient addition did not improve biofiltration performance. Supplementing hydrogen peroxide (<1 mg/L) decreased headloss, DBP formation potentials while adversely affecting UF fouling. In-line alum addition (<0.5 mg/L) improved biofilter’s ability to control fouling and DBP precursor without adversely impacting headloss. GAC provided superior performance when compared to anthracite. Conventional treatment provided higher DOC, and DBP precursor removal, as well as better UF fouling control compared to biofiltration.

A biofiltration system is a stormwater Best Management Practice (BMP) that uses a biologically active filtration bed to remove contaminants. This type of BMP is preferred because it provides the opportunity for pollutant uptake (particularly nutrients) by vegetation in an aesthetically pleasing design. The goals of this research, proposed by the City of Austin, Texas, are to assess the role of plants in nutrient removal and to compare the pollutant removal effectiveness of biofiltration systems containing different media, plant species and designs. A laboratory column study was conducted with nineteen experiments using synthetic stormwater and one experiment using real stormwater. The results of this study show a significant improvement in nutrient removal with the presence of plants and a submerged zone with a carbon source in the filter. The columns without plants were found to export up to twice the nitrate/nitrite input, whereas the columns with plants showed significant removal of all nutrients (Nitrate 30-50%, Total Kjeldhal Nitrogen 65-85%, Total Phosphorus 80-90%). The difference between the two biofiltration media was not significant. Metals (Copper, Lead, Zinc) removal by all columns was very high (>95%) compared to similar field studies. Total Suspended Solids removal remained high through the whole set of experiments for all the columns (85- 95%). / text

Recently, treatment plants have adopted biofiltration to compliment conventional treatment and ozonation. Previous literature has focused on passive applications of biofiltration. In this study, several pilot-scale biofiltration trains were designed in parallel to conventional treatment to investigate the impact of nutrient addition (nitrogen and phosphorus), use of hydrogen peroxide, aluminum sulphate (alum), and different filtration media (anthracite vs. granular activated carbon (GAC)) on biofiltration performance. Parameters measured included organic removal, reduction of DBP precursor, improvements in filter runtimes and ultrafiltration (UF) fouling control. Nutrient addition did not improve biofiltration performance. Supplementing hydrogen peroxide (<1 mg/L) decreased headloss, DBP formation potentials while adversely affecting UF fouling. In-line alum addition (<0.5 mg/L) improved biofilter’s ability to control fouling and DBP precursor without adversely impacting headloss. GAC provided superior performance when compared to anthracite. Conventional treatment provided higher DOC, and DBP precursor removal, as well as better UF fouling control compared to biofiltration.

Highway stormwater runoff contains a number of contaminants including nutrients and heavy metals that can be detrimental to the health of lakes, rivers, and streams. Biofiltration is a common stormwater treatment mechanism that can reduce nutrients and heavy metals through physical, chemical, and biological processes. Vegetation type has been shown to impact the removal of nutrients from stormwater runoff (Barrett et al. 2013; Read et al. 2008). The inclusion of a permanent saturated layer underneath the surface of a biofilter has been investigated to enhance denitrification and thus nitrogen removal (Kim et al. 2003; Zinger et al. 2007). Six Georgia native grasses as well as one turf grass have been tested in a column study along with a permanent saturated zone for biofiltration enhancement. Synthetic stormwater was used in this study. Two months of dosages with an average synthetic stormwater were monitored followed by one event with a heavy metal spiked synthetic stormwater, one event with a nutrient spiked synthetic stormwater, and one event with an average synthetic stormwater after two weeks of drought conditions. Biomass fly ash was also added to columns to determine potential benefits to biofiltration applications. Results indicated that Big Bluestem, Indiangrass, and Switchgrass when paired with a permanent saturated zone remove the highest percentage of total nitrogen across all experiments (4%, 13%, and 18% respectively). These species contained think and dense root systems that spanned the entirety of the biofilter column. Removal of nitrate was enhanced with a saturated zone while ammonium removal decreased. Nitrogen leaching from the columns may be reduced by utilizing soil of low organic content. Phosphorus, copper, lead, and zinc removal was not correlated with plant species; however, a permanent saturated zone increased removal of phosphorus, copper, and zinc (removal of lead was >97% in all cases making differences in removal insignificant). These results support the impact of specific vegetation types on the removal extent of total nitrogen. Saturation provided benefits of total nitrogen, phosphorus, copper, and zinc removal in terms of removal extents as well as consistency of treatment across all experiments. Field experimentation is encouraged to determine long term effects at a large scale.

Odour emissions resulting from reduced sulphur compounds in the kraft pulping industry are frequently found in dilute, high flowrate air streams that are costly to treat using incineration and thermal oxidation. Biofiltration, an air treatment method involving passing air through a packed bed of microorganisms, has emerged as a promising treatment strategy for these dilute waste gas streams. However, biodegradation of dimethyl sulphide (DMS) in biofilters is rather poor and is limiting the application of biofiltration to odour streams rich in DMS. Recently, our group has shown that co-treatment of DMS with methanol can increase DMS removal significantly. In this thesis, the effect of methanol on the microbiology of two biofilters treating DMS was explored. Microbial community analysis revealed that the addition of methanol led to a significant increase of up to an order of magnitude in the abundance of Hyphomicrobium spp. in a biofilter co-treating DMS and methanol compared to a biofilter treating DMS alone with no significant difference in the abundance of Thiobacillus spp. between the two biofilters. Further to the biofiltration experiments, the growth kinetics of Hyphomicrobium spp. and Thiobacillus spp. on DMS and methanol in an enrichment culture created from a biofilter co-treating DMS and methanol were studied. A specific growth rate of 0.099 h-1 and 0.11 h-1 was determined for Hyphomicrobium spp. and Thiobacillus spp., respectively, growing on DMS at pH 7, double the highest maximum specific growth rate for bacterial growth on DMS reported to date in the literature. As the pH decreased from pH 7 to pH 5, the specific growth rate of Hyphomicrobium spp. decreased significantly by 85% in the mixed culture while the specific growth rate of Thiobacillus spp. remained similar through the same pH shift. When methanol was used as a substrate, the specific growth rate of Hyphomicrobium spp. declined much less over the same pH range (up to 30%). These results suggest that addition of methanol to biofilters co-treating DMS and methanol can increase DMS removal rates by increasing the abundance of DMS-degrading Hyphomicrobium spp. at pH levels not conducive to high growth rates on DMS alone.

The ability of an upflow, denitrifying biofilter using a fermentation generated carbon source to treat the high nitrate concentrations typically seen in recirculating aquaculture systems was studied using a synthetic nitrate wastewater supplied at two nitrate loadings, 1.13 and 2.52 kg NO3-N/m3/day. A supplemental carbon source was provided primarily through the fermentation of fish food which generated volatile fatty acids (VFA) in the form of acetic, propionic, isobutyric, n-butyric, 2-methylbutyric, 3-methylbutyric, and n-valeric acids. Acetic and propionic acids were the predominant constituents generated, while lower concentrations of the longer carbon chain butyric and valeric acids were produced. The VFAs proved to be a viable carbon source for the denitrification process as indicated by the ability of the biofilm to assimilate all of the constituents generated. Carbon limiting the system resulted in an increase in effluent nitrite and incomplete nitrate removal. During the low nitrate loading condition, influent COD to NO₃-N ratios greater than 5 typically achieved high total nitrogen removals greater than 95%. This influent ratio corresponded with a COD to NOx -N consumption ratio of 4.62 ± 0.28 mg/L as COD per mg/L as N for complete nitrogen removal. Under the high nitrate loading condition, influent COD to NO₃-N ratios achieving high nitrogen removals showed great variability and did not correspond to a distinct value. The COD to NOx -N consumption ratios were often below stoichiometric values, which was attributed to the hydrolysis of influent fermentation solids captured within the column to generate a COD source not measured by filtered samples. The column biofilm kinetics were modeled using a half-order reaction rate and denitrification coefficients (k) of 0.70 ± 0.02 (mg NOx-N/L)1/2 / min and 1.18 ± 0.12 (NOx-N /L)1/2 / min were determined for the low and high nitrate loading phases, respectively. / Master of Science

Dans un contexte interdisciplinaire, l'étude a consisté à évaluer le niveau de robustesse de procédés pilotes de biofiltration appliqués au traitement d'un effluent caractéristique des émissions de compostage de boues d'épuration, soumis à des fluctuations de charge transitoires, répétées, et d'intensité croissante. L'impact de ces perturbations a été examiné à deux niveaux, par la mesure de la résultante fonctionnelle de dégradation d'une part, et par la caractérisation de la structure génétique de la communauté bactérienne totale d'autre part. La mise en relation de ces deux composantes a fait l'objet d'une attention particulière. / The study aimed to evaluate the robustness capacity of pilot-scale biofilters applied to the treatment of sludge-composting emissions. The biofilters were submitted to repeated periodic fluctuations (shock loads) of increasing intensity. Their response was evaluated at two levels: functional resistance and resilience in terms of removal efficiency, and molecular characterization of the bacterial community structure. The objective was to establish the potential links between these two components.