Tania Datta

Biocontrol of biomass bulking caused by Haliscomenobacter hydrossis using a newly isolated lytic bacteriophage

In a previous paper, the first ever application of lytic bacteriophage (virus)-mediated biocontrol of biomass bulking in the activated sludge process using Haliscomenobacter hydrossis as a model filamentous bacterium was demonstrated. In this work we extended the biocontrol application to another predominant filamentous bacterium, Sphaerotilus natans, notoriously known to cause filamentous bulking in wastewater treatment systems. Very similar to previous study, one lytic bacteriophage was isolated from wastewater that could infect S. natans and cause lysis. Significant reduction in sludge volume index and turbidity of the supernatant was observed in batches containing S. natans biomass following addition of lytic phages. Microscopic examination confirmed that the isolated lytic phage can trigger the bacteriolysis of S. natans. This extended finding further strengthens our hypothesis of bacteriophage-based biocontrol of overgrowth of filamentous bacteria and the possibility of phage application in activated sludge processes, the worlds widely used wastewater treatment processes.This research demonstrates the first ever application of lytic bacteriophage (virus) mediated biocontrol of biomass bulking in the activated sludge process using Haliscomenobacter hydrossis as a model filamentous bacterium. Bacteriophages are viruses that specifically infect bacteria only. The lytic phage specifically infecting H. hydrossis was isolated from the mixed liquor of a local wastewater treatment plant. The isolated bacteriophage belongs to the Myoviridae family with a contractile tail (length-126 nm; diameter-18 nm) and icosahedral head (diameter-81 nm). Titer of the isolated phage with H. hydrossis was calculated to be 5.2 ± 0.3 × 10(5) PFU/mL and burst size was found to be 105 ± 7 PFU/infected cell. The phage was considerably stable after exposure to high temperature (42 °C) and pH between 5 and 8, emphasizing that it can withstand the seasonal/operational fluctuations under real-time applications. Phage to host (bacteria) ratio for the optimal infection was found to be 1:1000 with ∼54% host death. The isolated phage showed no cross infectivity with other bacteria most commonly found in activated sludge systems, thus validating its suitability for biocontrol of filamentous bulking caused by H. hydrossis. Following the phage application, successful reduction in sludge volume index (SVI) from 155 to 105 was achieved, indicating improved biomass settling. The application of phage did not affect nutrient removal efficiency of the biomass, suggesting no collateral damage. Similar to phage therapy in medical applications, phage-mediated biocontrol holds a great potentiality for large-scale applications as economic agent in the mitigation of several water, wastewater and environmental problems. Present study in this direction is a novel effort.

Evaluation of simultaneous nutrient removal and sludge reduction using laboratory scale sequencing batch reactors

The treatment and disposal of excess sludge has been a rising challenge for wastewater treatment plants worldwide. In this study, simultaneous sludge reduction and nutrient removal was evaluated in laboratory scale sequencing batch reactors (SBRs). Two SBRs were operated alongside for a duration of 370d. One SBR was operated to achieve nutrient removal (control-SBR) at 10d solids retention time (SRT), while the other (modified-SBR) was operated to achieve nutrient removal along with sludge reduction. Sludge reduction in the modified-SBR was accomplished by subjecting the recycled biomass to feasting and fasting at sufficiently high SRT close to infinity (phase I and II) and finite SRT (phase III). The observed biomass yield in the modified-SBR was estimated to be 0.17mg TSSmg(-1) COD, representing 63% sludge reduction compared to the control-SBR. The NH(3) levels in the effluents from both SBRs always remained below detection limit. The average dissolved phosphorus removal efficiencies in the control-SBR and the modified-SBR were 87% and 84%, respectively, during phase II. However, the biomass of the modified-SBR increased during phase II. To control this, biomass wastage was initiated directly from the modified-SBR during phase III at a rate equivalent to the observed biomass accumulation rate in the system in phase II. This resulted in an overall 100d SRT for the modified-SBR system. Following this change, biomass accumulation in the modified-SBR was controlled, and a net 63% sludge reduction could be sustained along with 90% phosphorus and 100% NH3 removal. Consistent denitrification activities were also noticed in both SBRs despite the absence of any carbon source during the anoxic phase of every cycle.

Effect of organic carbon on ammonia oxidizing bacteria in a mixed culture.

This study examined the effect of organic carbon (peptone vs. glucose) on two sequencing batch reactors performing simultaneous carbon oxidation and nitrification. Although each reactor had similar COD oxidation kinetics (0.029 and 0.036 mg COD mg VSS(-1) h(-1)), the Monod nitrification kinetics for the peptone-fed reactor (mu(m)=2.72 h(-1), K(s)=17.8 mg N L(-1)) were faster than for the glucose-fed reactor (mu(m)=0.868 h(-1), K(s)=26.5 mg L(-1)). The overall bacterial communities were profiled by 16S rRNA cloning and sequencing and revealed homology with a greater variety of bacteria from the peptone-fed reactor than the glucose-fed reactor. In addition, amoA cloning and sequencing, terminal restriction fragment length polymorphism, and fluorescent in situ hybridization experiments indicated greater AOB diversity and abundance in the peptone-fed reactor. This research provides evidence that the organic carbon source affects the make-up of the heterotroph community as well as AOB in mixed cultures.

Evidence and Long-Term Feasibility of Enhanced Biological Phosphorus Removal in Oxidation-Ditch Type of Aerated-Anoxic Activated Sludge Systems

This study investigated the potential of four full-scale oxidation ditches to accomplish enhanced biological phosphorus removal (EBPR). Despite the fact that none of the tested oxidation ditches were designed to perform EBPR, mixed liquors from all four ditches showed good specific phosphorus release and uptake rates, a typical characteristic of a typical EBPR biomass. The specific phosphorus release rates ranged from 0.042- to 0.254-mg P/mg VSS-d and the specific phosphorus uptake rates ranged from 0.023- to 0.125-mg P/mg VSS-d for the tested full-scale plants. The EBPR potential of one of the full-scale plants (Central Davis Sewer District) was further studied by changing the aeration patterns in the ditch. The mixed liquor in this full-scale plant exhibited good phosphorus release and uptake trends and dissolved phosphorus, as low as 1.26 mg/L, could be accomplished in the final effluent of this plant as a result of this optimization. The long-term feasibility of the EBPR in this full-scale was tested ...

Organic carbon effect on nitrifying bacteria in a mixed culture

This study investigated the effect of organic carbon source on ammonia oxidizing community in single sludge laboratory scale sequencing batch reactors (SBR). Two sequencing batch reactors performing simultaneous carbon oxidation and nitrification were operated. Operationally and functionally, these two reactors were identical, except that one reactor was fed peptone and sodium acetate, and the other was fed glucose and sodium acetate as external organic carbon sources. The peptone-fed reactor had 98.1 + or - 1.84% COD removal and 97.3 + or - 6.69% NH(3)-N oxidation. The glucose-fed reactor had 99.1 + or - 1.29% COD removal and 99.4 + or - 0.76% NH(3)-N oxidation. The reactor fed with peptone, a complex organic carbon source comprised of enzymatic digests of animal proteins, had greater diversity in both the heterotrophic bacterial community and the ammonia oxidizing bacteria community than in the reactor fed with glucose, a simple sugar as evidenced by automated ribosomal intergenic spacer analysis (ARISA) and terminal restriction fragment length polymorphism (TRFLP) experiments respectively.

Seasonal variations of nitrifying community in trickling filter-solids contact (TF/SC) activated sludge systems

Two full-scale trickling filter/solids contact (TF/SC) basin plants, each successfully performing nitrification, were sampled throughout various seasons over a period of one year. Concentrations of ammonia, nitrate and nitrite were measured at various sampling locations along the treatment train. DNA was also extracted from mixed liquor in the solids contact basins. These DNA samples were subjected to terminal restriction fragment length polymorphism (TRFLP) in order to profile the ammonia oxidizing bacteria and nitrite oxidizing bacteria communities. In both plants, there was a prevalence of Nitrosomonas europaea among the ammonia oxidizing bacteria (AOBs). However, during the summer months, there was increased diversity of Nitrosomonas species. Likewise, Nitrospira spp. was the dominant nitrite oxidizing bacteria (NOBs) in both plants regardless of season. Yet there was an increased presence of Nitrobacter among the NOBs in the summer months. These results add an important understanding of the ecology and dynamics in nitrifying population in full-scale TF/SC wastewater treatment plants.

Evaluating the role of point source discharges informs statewide nutrient control policy in Utah.

An evaluation of costs, rate, and environmental impacts of upgrading publically owned treatment works (POTWs) in the State of Utah to four levels of nutrient control allowed a variety of nutrient control policies to be assessed. Upgrade costs and rate impacts indicated that costs would be within a defined range for many POTWs, especially with design capacities greater than 40,000 m3/day (-10 mgd). However, costs were significantly higher for some POTWs with lower design capacities, and nutrient upgrades to the most stringent levels would not be affordable for these communities, representing about 15 percent of the service population. The resulting equity issues can be addressed through hardship grants program and/or regulations based on a trading scheme. Analysis demonstrated that trading offers advantages, including cost efficiency and flexibility to accommodate further nutrient reductions and population growth, and greater ability to interface with urban and rural nonpoint nutrient control. Currently, the State of Utah is establishing technology-based nutrient limits that can be affordably implemented at all POTWs in phases. Additionally, a multi-faceted approach is being evaluated that will consider prioritized watershed-scale strategies, point and nonpoint sources of pollution, ecological and socioeconomic implications, and stakeholder participation in nutrient reduction programs.

Evaluating analytical methods for the characterization of lipids, proteins and carbohydrates in organic substrates for anaerobic co-digestion.

This study provides insights into the characterization of lipids, proteins and carbohydrate content in substrates for codigestion, and evaluates their effects on biogas yield. Among the analytical methods evaluated, the Bligh and Dyer, Hach Total Nitrogen and the Anthrone method were found to be most suitable for lipids, proteins and carbohydrates analysis, respectively. The co-digestibility of ten co-substrate mixes prepared using various volume-to-volume ratios of foodwaste (FW), fats, oils and grease (FOG), and waste activated sludge (WAS) were tested using biomethane potential assays. The three main substrates were mono-digested as well. WAS mono-digestion yielded the lowest methane yield of 118mL CH4/g VS, while a 50:50 mix of WAS and FOG, containing 85% lipid and 15% protein produced the highest methane yield of 1040mL CH4/g VS. In general, lipid-rich samples yielded more biogas than samples rich in proteins and carbohydrates. However, samples rich in proteins and carbohydrates had faster biogas production rates.