Search

The main objective of this study was the comparison of activated sludge reactors with reactors containing biocarriers using a wastewater containing phenanthrene as a model compound simulating the presence of toxic substances. Five sequencing batch reactors were used. One contained a porous polyvinyl alcohol gel (PVA-gel) biocarrier and another had a high-density polyethylene biocarrier, while the other three reactors consisted of conventional activated sludge. The addition of phenanthrene at low concentration (15 μg/L in influent wastewater) did not adversely affect the removal efficiencies of chemical oxygen demand (COD) and ammonium (i.e. nitrification performance). However, with a higher addition of phenanthrene (150 μg/L in influent wastewater), a reduction in COD removal efficiency and an inhibitory effect on denitrification was observed. Generally, nutrient removal was poor, with the exception of denitrification in the reactor containing the PVA-gel. It seems that PVA-gel beads allow the for...

A survey of wastewater treatment facilities in the Federated States of Micronesia revealed a lack of fully functional treatment systems and conditions that potentially could lead to adverse environmental impacts and public health concerns. Due to inadequate facilities, the amount and composition of wastewater entering the plants as well as the degree of treatment being achieved is largely unknown. In some cases raw sewage is being discharged directly into the ocean and waste sludge is regularly taken by local residents for agricultural purposes without adequate treatment. In addition, the need to establish best management practices for placement and maintenance of septic tanks is urgent. Furthermore, development of eco-friendly solutions is needed to more effectively treat wastewater from industrial and agricultural sources in an effort to abate current pollution problems. Comparisons of treatment methods being used and problems encountered at different locations in the islands would provide valuable information to aid in the development of sustainable treatment practices throughout Micronesia.

This paper presents a one-year-long study of the baseline hydrologic conditions of the Geus Watershed in the tropical island of Guam, through field observations. Data analyses show a strong correlation between stream level, turbidity, and rainfall within the watershed, suggesting a highly dynamic nature of Geus watershed. Field data were then used to create a stage discharge curve, which increases the efficiency of future watershed management by providing an estimate of stream flow from a simple measure of water level. The supplemental analyses based on the test results of soil samples and a GIS-based erosion model identified areas within the watershed with higher contributions to erosion potential. In addition, synthesis of the information in this watershed study will allow for future recommendations for effective and sustainable watershed management strategies, thereby opening a way for evaluating progress within the Geus watershed with continued monitoring.

Using an anionic surfactant, solubilization experiments were conducted with a suite of four very hydrophobic polycyclic aromatic hydrocarbons (PAHs)—fluorene, phenanthrene, fluoranthene and pyrene—in all possible combinations to explore interactions in the microenvironment of the micellar core. Fluorene and phenanthrene demonstrated mutually competitive solubilization effects; however, fluoranthene and pyrene were less consistent in their demonstration of competitive effects. As a preliminary observation, it was postulated that hydrocarbons with similar hydrophobicities (i.e., log Kow values) and melting points could compete for a similar locus in the micelle. In addition, with increasing number of solubilizates in a system, the total mass and volume of the solubilized product increased, with fluorene and phenanthrene demonstrating relatively greater contributions than fluoranthene and pyrene. Furthermore, the outer limits of the solubilization pattern approached a plateau of about 0.17 for Xm (0.20 for MSR) indicating a limiting maximum value, which conceptually could lend to an understanding of solubilization responses for multi-solubilizate systems as encounter in real remedial scenarios.

The use of a biomass carrier is preferred for the cultivation of slowly growing anammoxsludge. In this study, PVA gel was selected as a biomass carrier for anammox sludge audapplied in a fluidized-bed reactor (FBR). A recycle pump was used to induce a flow rateof 6 - 7 l/min to maintain fluidized bed conditions. Both influent NH4-N and NO2-Nconcentrations were increased stepwise to 300 mg N/l. With hydraulic retention times(HRTs) from 16 h to 9 h in phase 1, NH4-N and NO2-N removal efficiencies were about81% and 92%, respectively. With HRTs from 9 h to 4 h in phase 2, NH4-N removalefficiency was 77% and NO2-N removal efficiency was 89%. The removal rates ofammonium and total nitrogen in phase 1 increased up to 0.71 and 1.35 kg N/m3/d,respectively. Maximum removal rates of ammonium and total nitrogen in phase 2 increasedquickly up to 1.5 and 3.0 kg N/m3/d, respectively. Ratios of T-N removal, NO2-N removal,and NO3-N production to NH4-N removal during phase 1 were 1.91:1.12:0.22. These ratiosduring phase 2 were 1.96:1.18:0.21. The color of the PVA-gel beads changed from white tobrownish red, which is consistant with anammox bacteria. By the Denaturing Gradient GelElectrophoresis (DGGE) method, both KSU-1 and KU-2 anammox strains were detectedwith KSU-1 in dominance in the FBR process.

Swim-bed technology using the novel acryl-fiber biomass carrier--biofringe (BF) attachment material--demonstrated effective treatment of high-strength organic wastewater with 80% COD removal efficiencies at high volumetric loadings up to 12kg/m3/d with a hydraulic retention time of 3 h. BF material allowed for attachment of large amounts of biomass in a matrix that flexes with the wastewater flow, thus providing a high degree of contaminant-biomass contact in a fully retainable biofilm. As much as 133 g of biomass per meter of BF was retained for an equivalent 13.3 g/l with respect to the BF retention or reaction zone. Limited evidence for nitrification occurred only at low COD loading rates (ca.1.6 kg/m3/d) . In addition, filamentous biomass growth was very heavy at the lower loading rates, but was avoidable at COD loadings of 8kg/m3/d or greater. The levels of extracellular polymers--proteins in particular--in the biofilm were very high compared to levels reported for flocculent or granular sludges. While treatment in this study focused on industrial level applications, the possibility of using this technology in other treatment scenarios involving lower organic loadings was discussed.

Using a nonwoven material for biofilm attachment in a continuous flow reactor, conversions of nitrogenous compounds closely following the stoichiometry of the recently discovered anaerobic ammonium oxidation(anammox)process were developed and maintained for over one year of operation. Removal rates of ammonium(NH4+)and total nitrogen as high as 31 and 63 mg N/(l・h), respectively, were demonstrated over several weeks of operation and removals of approximately 24 and 47 mg N/(l・h), respectively, were maintained over most of the study, which are in a suitable range for industrial applications. With a HRT of 8.5 hours, influent NH4+ and nitrite(NO2-) concentrations of over 300 mg N/l, each, were successfully treated with removal efficiencies of approximately 70%. However, very little benefit could be attributed to the use of recycle in attempts to work with higher influent concentrations where NO2toxicity would be of concern.

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.

Research was conducted to further evaluate a denitrifying upflow sludge-blanket (USB) unit process for treatment of soft groundwater amended to a high pH as previously shown to be essential for effective granulation. From kinetic studies, a saturation constant of 15 mg-N/l was determined reflecting a high affinity of the granular sludge for the ethanol-nitrate substrate. The influence of carbon loading during the course of continuous treatment runs demonstrated that nitrite persisted in the effluent at carbon to nitrogen ratios below 1.1. Groundwater samples polluted with nitrate were obtained from two towns in Kumamoto Prefecture and used in continuous treatment experiments. Influent nitrate as high as 29 mg-N/l was completely removed at a HRT of only 30 min. The characteristics of these groundwaters without chemical additions (other than pH adjustment) were well suited for subsistence of granular sludge with good retention characteristics. Discussion was offered to establish protocol for progressing to actual treatment in the field, which should be possible for groundwaters of low hardness common to Japan with only minimal chemical adjustments (e.g., pH) at the treatment site.

Research was conducted to probe for useful applications of less commonly considered nitrogen bio-transformation processes including anaerobic ammonium oxidation (anammox) using continuous flow treatment with a non-woven biomass carrier for enrichment of slowly growing organisms. Reactors were seeded with sludge from an industrial denitrification unit process. Following seven weeks of operation under autotrophic anoxic conditions, disappearances of ammonium and nitrite with production of low levels of nitrate were evidenced at stoichiometric ratios approximating that of the anammox reaction documented at Delft University of Technology, The Netherlands. In subsequent loading rate studies, ammonium and total-nitrogen removal rates of 8.7 and 18.8 mg N l-1h-1, respectively, were achieved (hydraulic retention time, 9 h) . Furthermore a distinctly red biomass growth developed which is characteristic of the responsible microorganism (s) . The sequence of a 16S rDNA clone obtained from the red biomass matched that previously reported for the planctomycete firstly identified responsible for the reaction with a similarity score of 0.928 (99.1% sequence similarity) . To our knowledge, this constitutes the first substantiated confirmation of the biological anammox reaction outside of Europe.

A survey was conducted of the wastewater treatment systems and related sludge handling practices on the island of Yap, in the Federated States of Micronesia, to assist in identifying areas where further work would be merited to improve on effectiveness and sustainability. A detailed inventory was made of communal septic tanks as found at health centers and schools. Though most of these septic tanks appeared to be functional, there were concerns due to some units being positioned within the tidal zone, covered over with vegetation, or out of reach of the pump truck. Furthermore, the centralized wastewater treatment plant on Yap provides only primary treatment consisting of a limited removal of suspended solids. Thus, only partially treated sewage is being discharged to the bay. Excess sludge is drawn from the treatment plant on a quarterly basis, which local farmers regularly make use of as fertilizer for crop application without adequate treatment. As an immediate target for further study and pilot testing, exploring the use of an attached-growth process as an inexpensive retrofit to enhance the effectiveness of the treatment plant is proposed. In addition, the benefits of implementing a composting program for recycle of waste sludge in a safe manner and developing a framework for management of septic tanks are discussed.

Nitrate removal from soft groundwater using ethanol as a carbon source in an upflow sludge-blanket reactor containing denitrifying granular sludge was investigated. At a hydraulic retention time of 0.83 h, influent nitrate was increased stepwise from 20 to 145 mg N/l (volumetric loading rates (VLRs), 0.60 to 4.2 g N/l/d, respectively) and sludge was periodically wasted to maintain a sludge bed of about 2 3 the liquid volume. Complete nitrate removal was achieved at influent nitrate concentrations up to 75 mg N/l(2.1 g N/l/d). MLSS increased from 20 g/l at a VLR of 0.6 g N/l/d to 51 g/l at a VLR of 1.9 g N/l/d, above which it decreased. VSS increased from 11 g/l to a maximum of 25 g/l at a VLR of 2.1 g N/l/d. Settling velocities showed the same trend with maximum values in a VLR range of 1.5 to 2.1 g N/l/d. However, granule size, calcium and magnesium contents of the granular sludge and protein, carbohydrate and nucleic acid contents of extracellular polymers decreased steadily with an increase in VLR throughout the range of testing. Within the VLR range of 0.6 to 2.1 g N/l/d, corresponding to complete nitrate removal and efficient sludge retention, the granular sludge had a high calcium content of 24 to 22%, magnesium ranged from only 0.7 to 0.1%, proteins from 3.2 to 1.3%, carbohydrates from 4.2 to 1.4%, and nucleic acids from 0.34 to 0.05% of the sludge dry weight. These results suggest an optimum operational VLR in terms of nitrate removal and sludge retention of about 2 g N/l/d.

Microorganisms have demonstrated considerable versatility in cycling nitrogenous compoundsin natural and engineered environments. Experiments were conducted to study the controllability and potential applications of these less commonly considered phenomena. Stressed biological systems, lacking oxygen and labile organic compounds, with reduced and oxidized nitrogen substrates were investigated. Results demonstrated conversions of soluble nitrogenous compounds that could not be fully explained by traditional nitrification or denitrification. Comparisons are made to reports of others and discussed in terms of environmental engineering significance and items of interest that merit further inquiry are identified.

Biological denitrification using sponge carriers for retention of biomass in a fluidized bed reactor with gas recirculation was investigated. Using ethanol as a carbon source, nitrate contaminated groundwater (20 mg/l as nitrogen) was treated at various hydraulic retention times (HRT) and carbon to nitrogen ratios (C: N) to assess system capabilities. Near complete removal of influent nitrate was achieved with a C: N of 1.9 or greater at a HRT of 1.25 hours. A gradual reduction in C: N from 1.9 to 1.0 resulted in a concurrent reduction in nitrogen removal efficiency to about 65%. However, removal efficiencies of total organic carbon (TOC) were improved from about 75% (at C: N of 1.9) to 95% (at C: N of 1.0) with effluent TOC concentrations falling below 2.0 mg/l. The benefits of operation with reduced TOC and solids output at the expense of nitrogen removal efficiency was discussed. The sponge biocarriers demonstrated favorable potential for retention of essential biomass in a denitrification unit process.

In biofilm systems, treatment performance is primarily dependent upon the available biofilm growth surface area in the reactor. Specific surface area is thus a parameter that allows for making comparisons between different carrier technologies used for wastewater treatment. In this study, we estimated the effective surface area for a spherical, porous polyvinyl alcohol (PVA) gel carrier (Kuraray) that has previously demonstrated effectiveness for retention of autotrophic and heterotrophic biomass. This was accomplished by applying the GPS-X modeling tool (Hydromantis) to a comparative analysis of two moving-bed biofilm reactor (MBBR) systems. One system consisted of a lab-scale reactor that was fed synthetic wastewater under autotrophic conditions where only the nitrification process was studied. The other was a pre-denitrification pilot-scale plant that was fed real, primary-settled wastewater. Calibration of an MBBR process model for both systems indicated an effective specific surface area for PVA gel of 2500 m2/m3, versus a specific surface area of 1000 m2/m3 when only the outer surface of the gel beads is considered. In addition, the maximum specific growth rates for autotrophs and heterotrophs were estimated to be 1.2/day and 6.0/day, respectively.

Experiments were conducted to evaluate the potential of ether sulfate surfactants with degrees of ethoxylation ranging from one to four per molecule for use in subsurface remediation. It was hypothesized that ethoxylated anionic surfactants will exhibit lower losses in the subsurface due to precipitation and sorption as a function of increasing ethoxylation while maintaining high hydrocarbon solubilization potentials. Results demonstrated that no significant precipitation of surfactant and calcium occurred where the degree of ethoxylation was two or greater. Sorption assays demonstrated that these ethoxylated anionic surfactants were less prone to sorption on soil than nonethoxylated anionic and nonionic surfactants. Furthermore, enhancements in solubilization of naphthalene were evidenced with increasing degrees of ethoxylation, and micelle-water partition coefficients were comparable with those of other high-performance surfactants. Microbial degradation assays indicated that these ethoxylated anionic surfactants served readily as substrates, raising concerns relative to their use in subsurface aerobic systems. However, they could be compatible with a treatment train concluded with a biological unit process.

Polyvinyl alcohol (PVA) gel beads cultivated in an upflow anaerobic sludge-blanket reactor treating synthetic corn steep liquor (CSL) wastewater were used to seed a lab-scale anaerobic fluidized-bed (AFB) reactor also treating CSL. Under steady-state conditions in the AFB reactor, a COD removal efficiency in excess of 96% was achieved at an organic loading rate (OLR) of 25 g/l/d with a hydraulic retention time (HRT) of 10 h. Furthermore, a removal efficiency of 91% was achieved at an OLR of 27.5 g/l/d with an HRT of only 6 h. With a biomass attachment 1.02 g VSS/g PVA-gel beads, the biomass concentration in the AFB reactor was approximately 610 g/l, while for natural granules only 100 g/l is considered possible. Over the study period, the granular PVA gel turned from black to gray while the biomass attached on the outer surface of the beads also changed in composition. In addition, observations of the interior of the gel beads showed that colonization had progressed well into the core, indicating that effective substrate diffusion occurred within the PVA-gel matrix under the good substrate-microorganism contact conditions provided by the AFB reactor.

Maintenance of denitrifying granular sludge for treating soft groundwater (total hardness = 75 mg calcium carbonate/L) in an upflow sludge-blanket reactor was demonstrated with complete removal of applied nitrate (20 mg N/L) over extended operation and a hydraulic residence time of 34 minutes. A high pH of approximately 9.0 was shown to be important for generation of mineral precipitation needed for production of heavy granular sludge with good retention characteristics. As a method of increasing precipitation potential, pH adjustment was determined to be more economically favorable than calcium or alkalinity supplementation. In addition, temporary increases in substrate loading were shown to be effective for enhancing biomass levels in a manageable granular sludge. The significance of biomass in promoting mineral precipitation was discussed.