Robert Delatolla

In situ characterization of nitrifying biofilm: minimizing biomass loss and preserving perspective.

Methods for characterizing nitrifying bacteria within biofilms are of key importance to understand and optimize the nitrification kinetics of attached growth treatment facilities. In this work, we propose an analytical protocol based upon environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy (CSLM) in combination with fluorescent in situ hybridization (FISH) to characterize the structure of nitrifying biofilm as it remains attached to the original reactor substratum. This protocol minimizes the loss of mass and distortion of in situ perspective commonly associated with traditionally applied microscopic techniques and thereby enables a more accurate estimation of the nitrifying biomass within biofilm attached to the substratum. The use of ESEM eliminates the destructive preparatory procedures associated with traditional scanning electron microscopy and thus the loss of mass and shrinking of the samples. ESEM is used in this study to evaluate the percent coverage of the substratum with biofilm and the biofilm thickness. CLSM-FISH is used to determine cell counts in the biofilm and to characterize the undisturbed substratum/biofilm interface. By hybridizing and analyzing the nitrifying biofilm using CLSM as it remains attached to the substratum, the loss of material and distortion of in situ perspective associated with the biofilm detachment process is minimized. Moreover, by conducting the CLSM analysis directly on the nitrifying biofilm as it remains attached to the substratum it is shown that cell counts at the substratum/biofilm interface differ significantly from that located above the interface.

Meso and micro-scale response of post carbon removal nitrifying MBBR biofilm across carrier type and loading

This study investigates the effects of three specific moving bed biofilm reactor (MBBR) carrier types and two surface area loading rates on biofilm thickness, morphology and bacterial community structure of post carbon removal nitrifying MBBR systems along with the effects of carrier type and loading on ammonia removal rates and effluent solids settleability. The meso and micro analyses show that the AOB kinetics vary based on loading condition, but irrespective of carrier type. The meso-scale response to increases in loading was shown to be an increase in biofilm thickness with higher surface area carriers being more inclined to develop and maintain thicker biofilms. The pore spaces of these higher surface area to volume carriers also demonstrated the potential to become clogged at higher loading conditions. Although the biofilm thickness increased during higher loading conditions, the relative percentages of both the embedded viable and non-viable cells at high and conventional loading conditions remained stable; indicating that the reduced ammonia removal kinetics observed during carrier clogging events is likely due to the observed reduction in the surface area of the attached biofilm. Microbial community analyses demonstrated that the dominant ammonia oxidizing bacteria for all carriers is Nitrosomonas while the dominant nitrite oxidizing bacteria is Nitrospira. The research showed that filamentous species were abundant under high loading conditions, which likely resulted in the observed reduction in effluent solids settleability at high loading conditions as opposed to conventional loading conditions. Although the settleability of the effluent solids was correlated to increases in abundances of filamentous organisms in the biofilm, analyzed using next generation sequencing, the ammonia removal rate was not shown to be directly correlated to specific meso or micro-scale characteristics. Instead post carbon removal MBBR ammonia removal kinetics were shown to be related to the viable AOB cell coverage of the carriers; which was calculated by normalizing the surface area removal rate by the biofilm thickness, the bacterial percent abundance of ammonia oxidizing bacteria and the percentage of viable cells.

Rapid and reliable quantification of biofilm weight and nitrogen content of biofilm attached to polystyrene beads

Increased popularity of attached-growth wastewater treatment systems (e.g. biological aerated filtration processes-BAF) has created the need for a rapid and reliable method of characterizing biofilms. In addition to the mass of the biofilm that may serve as a control parameter for attached-growth treatment systems, the nitrogen content of the biofilm is also of great interest with increasingly strict nitrogen removal guidelines. Existing methods that may be used to analyse biofilms in such processes involve complex sample preparation and microbiological expertise that limit their application in many biofilm wastewater treatment studies and at existing treatment facilities as a feasible method of monitoring the biofilm. This paper describes a simple technical procedure that enables biofilm samples attached to polystyrene beads to be characterized in terms of the biofilm mass and the nitrogen content of the biofilm. The proposed protocol incorporates an agitation procedure that demonstrates 99.9% removal of the biofilm from polystyrene beads; a modified TSS procedure that measures the removed biofilm mass; and subsequently a modified total Kjeldahl nitrogen (TKN) procedure that enables the nitrogen content of the biofilm to be measured directly on the filter. Moreover, this protocol allows numerous beads to be analysed with limited manipulation and without the loss of critical mass.

Field study of moving bed biofilm reactor technology for post-treatment of wastewater lagoon effluent at 1°C

The goal of this study was to investigate the potential use of moving bed biofilm reactor (MBBR) systems as ammonia removal post-treatment units for wastewater (WW) treatment lagoons that demonstrate large temperature changes throughout their operational year (1−20°C). The study was carried out over a six-month period using laboratory-scale MBBR reactors fed with incoming effluent from a full-scale lagoon. The study shows that significant average ammonia removal rates of 0.26 and 0.11 kg N/m3·d were achieved at 20°C and 1°C. The increase in the ammonia removal rates with increasing temperature from 1°C to 20°C showed a strong correlation to an applied temperature correction coefficient model. No significant accumulation of effluent nitrite was observed at 1°C or after being fed with synthetic wastewater (SWW); indicating that cold temperatures and transitions from real WW to SWW did not stress the nitrifiers. Furthermore, the study demonstrates that changes in temperature or changes from real WW to SWW do not affect the mass of biofilm attached per MBBR carrier. Hence, based on the results of this study, it is concluded that MBBR is a promising technology for post-treatment ammonia removal of WW lagoon effluent.

Investigation of settleability of biologically produced solids and biofilm morphology in moving bed bioreactors (MBBRs)

Abstract The objective of this work is to investigate the effects of surface area loading rates (SALRs) and hydraulic retention times (HRTs) in moving bed bioreactor (MBBR) systems on the morphology and thickness of the attached biofilm along with subsequent effects on particle size distribution and the settling characteristics of the biologically produced solids. The morphology of biofilm attached to the MBBR carriers changed from a porous biofilm to a biofilm with a more filamentous structure throughout the study at various operating conditions without observable correlation with SALR and HRT. Although, biofilm morphology did not demonstrate an effect on the biologically produced solids observed in this study, the thinnest biofilms resulted in the highest concentration of solids in the effluent. Furthermore, the particle size distribution analysis demonstrated that both higher SALRs and longer HRTs resulted in a shift towards larger-sized particles. Increases in SALR and HRT, independent of each other, also showed increases in effluent solid concentration and lower settleability of the solids.

Kinetic analysis of attached growth nitrification in cold climates

The rate of nitrification within a laboratory-scale Biological Aerated Filtration treatment system at 4 degrees C was investigated during an exposure time of approximately four months (acclimatized experiments). In addition, shock experiments from 20 degrees C to 4 degrees C and from 4 degrees C to 20 degrees C were performed. The acclimatized experiments demonstrated that the exposure time the system remained at low temperature strongly affects the rates of nitrification. Nevertheless, the experiments showed that significant nitrification rates are maintained for up to 115 days at 4 degrees C. The rate of ammonia removal after an exposure time of 115 days at 4 degrees C was shown to be as high as 16% of the rate of removal observed at 20 degrees C. The 20 degrees C to 4 degrees C shock experiment demonstrated a 56% decrease in the rate of ammonia removal. On the other hand, the 4 degrees C to 20 degrees C shock experiment demonstrated an increase in the relative rates of ammonia removal of up to 300% when compared to rates of removal measured after 115 days at 4 degrees C. Thus, although the rates of nitrification have been shown to decrease significantly as a function of exposure time at 4 degrees C, the process has demonstrated important rates of ammonia removal at 4 degrees C for the approximate span of the North American winter.

Pilot-scale tertiary MBBR nitrification at 1°C: characterization of ammonia removal rate, solids settleability and biofilm characteristics

ABSTRACT Pilot-scale moving bed biofilm reactor (MBBR) is used to investigate the kinetics and biofilm response of municipal, tertiary nitrification at 1°C. The research demonstrates that significant rates of tertiary MBBR nitrification are attainable and stable for extended periods of operation at 1°C, with a maximum removal rate of 230 gN/m3 d at 1°C. At conventional nitrogen loading rates, low ammonia effluent concentrations below 5 mg-N/L were achieved at 1°C. The biofilm thickness and dry weight biofilm mass (massdw) were shown to be stable, with thickness values showing a correlation to the protein/polysaccharide ratio of the biofilm extracellular polymeric substances. Lastly, tertiary MBBR nitrification is shown to increase the effluent suspended solids concentrations by approximately 3 mg total suspended solids /L, with 19–60% of effluent solids being removed after 30 min of settling. The settleability of the effluent solids was shown to be correlated to the nitrogen loading of the MBBR system.

Carrier effects on tertiary nitrifying moving bed biofilm reactor: An examination of performance, biofilm and biologically produced solids

ABSTRACT Increasingly stricter ammonia and nitrogen release regulations with respect to wastewater effluents are creating a need for tertiary treatment systems. The moving bed biofilm reactor (MBBR) is being considered as an upgrade option for an increasing number of wastewater treatment facilities due to its small footprint and ease of operation. Despite the MBBRs creation as a system to remove nitrogen, recent research on MBBR systems showing that the systems performance is directly related to carrier surface area and is irrespective of carrier shape and type has been performed exclusively on chemical oxygen demand (COD) removal systems. Furthermore, the influence of carrier type on the solids produced by MBBR systems has also been exclusively studied for COD removal systems. This work investigates the effects of three specific carrier types on ammonia removal rates, biofilm morphology, along with solids production and settleability of tertiary nitrifying MBBR systems. The study concludes that carrier type has no significant effect on tertiary nitrifying MBBR system performance under steady, moderate loading conditions. The research does however highlight the propensity of greater surface area to volume carriers to become clogged under high loading conditions and that the high surface area carriers investigated in this study required longer adjustment periods to changes in loading after becoming clogged.

Disinfection byproduct formation during biofiltration cycle: Implications for drinking water production

The goal of this study was to investigate the potential of biofiltration to reduce the formation potential of disinfection byproducts (DBPs). Particularly, the work investigates the effect of the duration of the filter cycle on the formation potential of total trihalomethanes (TTHM) and five species of haloacetic acids (HAA5), dissolved oxygen (DO), organic carbon, nitrogen and total phosphorous concentrations along with biofilm coverage of the filter media and biomass viability of the attached cells. The study was conducted on a full-scale biologically active filter, with anthracite and sand media, at the Britannia water treatment plant (WTP), located in Ottawa, Ontario, Canada. The formation potential of both TTHMs and HAA5s decreased due to biofiltration. However the lowest formation potentials for both groups of DBPs and or their precursors were observed immediately following a backwash event. Hence, the highest percent removal of DBPs was observed during the early stages of the biofiltration cycle, which suggests that a higher frequency of backwashing will reduce the formation of DBPs. Variable pressure scanning electron microscopy (VPSEM) analysis shows that biofilm coverage of anthracite and sand media increases as the filtration cycle progressed, while biomass viability analysis demonstrates that the percentage of cells attached to the anthracite and sand media also increases as the filtration cycle progresses. These results suggest that the development and growth of biofilm on the filters increases the DPB formation potential.

Emerging investigators series: hydrogen sulfide production in municipal stormwater retention ponds under ice covered conditions: a study of water quality and SRB populations

Stormwater retention ponds have become an integral component of stormwater management across the world. Under prolonged hypoxia, these ponds are capable of releasing large quantities of hydrogen sulfide (H2S) gas. In this study, water quality constituents and bacterial communities in sediment were analyzed in two stormwater retention ponds, RSP1 (reference pond) and RSP2 (problematic pond) over a period of two years, to identify the factors driving H2S production and understand the microbial community associated with H2S production in stormwater ponds. It was found that the background total sulfide concentrations were not statistically different between the two ponds during summer (RSP2: 0.012 ± 0.001 mg L-S−1; RSP1: 0.010 ± 0.001 mg L-S−1) and were statistically different during ice covered winter operation (RSP2: 6.375 ± 1.135 mg L-S−1; RSP1: 0.016 ± 0.009 mg L-S−1). The study showed a lack of correlation between total sulfide concentrations in RSP2 and soluble chemical oxygen demand, sulfate, soluble total phosphorus, total ammonia nitrogen, nitrate, nitrite and pH. However, DO concentrations demonstrated a strong negative correlation with total sulfides concentrations in RSP2 (p < 0.006, r = −0.58, n = 26), which confirmed DO as the critical water quality parameter linked to H2S production in stormwater ponds. Finally, it was found that seasonal change, ice covered versus non-ice covered operation and a comparison between a H2S emitting pond and non-emitting pond all did not promote a measurable proliferation of sulfate-reducing bacteria nor a community shift in the sulfate-reducing bacterial population. Hence, the study demonstrates that sulfide production is a result of increased ubiquitous SRB activity in stormwater retention ponds and the emission of H2S gas is not indicative of SRB proliferation or a population shift towards specific SRB taxa.