Remediation potential of mulch for removing lead.

Hardwood bark mulch has good physicochemical properties for the adsorption of lead (Pb(II)). Batch tests were conducted to obtain the sorption coefficient of Pb(II) in mulch. The results of the Freundlich model were not in as good agreement as for the case of the Langmuir model. In addition, a laboratory-scale mulch permeable reactive barrier (PRB) system was designed for the treatment of Pb(II)-contaminated groundwater. The mulch PRB system, using a mulch layer, can potentially be used in the subsurface for cost-effective and in situ transformation of the Pb(II) into environmentally acceptable forms. From the Pb(II) breakthrough curve, the mulch becomes saturated more quickly at higher flow rates.

Development of polymer lab-on-a-chip (LOC) for oxidation-reduction potential (ORP) measurement.

Reverse osmosis (RO) desalination has been recognized as a promising method to solve the water shortage problem. Nevertheless, since it is energy intensive and has many problems associated with biofouling/fouling of RO membranes in RO plants, its commercial acceptance is still slow. Especially, as high levels of oxidizing agents negatively affect RO membrane efficiency and life span. So, there is a need to develop sensitive, selective, portable and rapid methods to determine oxidation-reduction potential (ORP) in feed solution. For developing a polymer ORP lab-on-a-chip (LOC), a microchannel patterned on a polymer substrate was successfully filled with 800 nm diameter silica beads using self-assembly bead packing technology. The measured ORPs using the three kinds of redox potential solutions were typically slightly lower than those of the nominal redox potential. But, all of the measurements should be deemed acceptable. The ORP LOC has also a much shorter response time than the conventional potentiometric sensor.

Development of a portable analyzer with polymer lab-on-a-chip (LOC) for continuous sampling and monitoring of Pb(II).

A new portable analyzer with polymer lab-on-a-chip (LOC) has been designed, fabricated and fully characterized for continuous sampling and monitoring of lead (Pb(II)) in this work. As the working electrodes of the sensor, bismuth (Bi (III)) which allowed the advantage of being more environmentally friendly than traditional mercury drop electrodes was used, while maintaining similar sensitivity and other desirable characteristics. The size of a portable analyzer was 30 cmx23 cmx7 cm, and the weight was around 3 kg. The small size gives the advantage of being portable for field use while not sacrificing portability for accuracy of measurement. Furthermore, the autonomous system developed in coordination with the development of new polymer LOC integrated with electrochemical sensors can provide an innovative way to monitor surface waters in an efficient, cost-effective and sustainable manner.

The role of biofilms in water reclamation and reuse.

Biofilms play a major role in many water reclamation and reuse technologies. Normally, wherever there is water, a support surface and nutrients available, a biofilm will form. In some cases, this may result in problems for the water treatment system, due to biofouling or the growth of pathogenic or other unwanted microbes, but more frequently, the biofilm serves a very useful purpose by biodegrading organic contaminants in the water or by converting unwanted inorganic materials into harmless ones. Biofilms are commonly found associated with membrane reactors and filtration systems used in water reclamation and reuse systems, and are often a critical component. They are also found in soils where they may impact water injection or removal systems, or in situ bioremediation. Knowledge of the way biofilms form, how they grow and how to control them is critical for effective design and operation of many water reclamation facilities. This paper explores the modes of formation and growth of biofilms, modern methods for exploring the structure and function of biofilms, and how to control their growth. This paper also presents details on our development of microelectrode sensor arrays for continuous soil pore water quality monitoring.

Application of mulch for treating metals in urban runoff: batch and column test.

Among the many methods available for the removal of heavy metals in urban nonpoint source pollution (NSP), adsorption has been shown to be an economically feasible alternative. To adsorb the amount of heavy metals in runoff, filtration of runoff through a specially constructed filter system is one possible treatment method. The mulch layer in a specially constructed filter system functions through adsorptive-filtration, where some pollutants are immobilised through sorption and some pollutants associated with suspended solids are immobilised through filtration. Therefore, the major interest of this study was to investigate the possibility of utilising mulch for the adsorption of heavy metals such as cadmium, copper, lead and zinc for a solution typical of those found in urban runoff using the flask-type adsorption batch tests and laboratory column tests. From the equilibrium sorption batch tests, it was observed that the adsorption of heavy metals on mulch with the same initial concentrations of metals in the solution decreased in the order Pb(II) > Cu(II) > Zn(II) > Cd(II) regardless of changes in pH. In column tests, the breakthrough curves for various heavy metals' adsorption by mulch showed that the binding strength of the following metal ions onto mulch was as follows: Pb(II) > Cu(II) > Zn(II) > Cd(II).

Development of a phosphate ion-selective microelectrode and its use in studies of the enhanced biological phosphorus removal (EBPR) process.

In an enhanced biological phosphorus reactor (EBPR), most poly-phosphate accumulating microorganisms (PAOs) exist as microbial aggregates, or flocs. Information contributing to a better understanding of the internal structure and function of flocs can lead to improvements in the modeling, design and operation of EBPR systems in wastewater treatment. A phosphate ion-selective microelectrode has been developed and was used to measure the phosphate profiles in flocs. The microelectrode uses cobalt as the sensing material and shows very good selectivity towards orthophosphate ions (H2PO4(-), HPO4(2-) and PO4(3-)). The potentiometric response showed a linear relationship with the logarithm of phosphate concentrations, with a slope of 31.5 mV per decade change of concentration. The solution pH did not show a significant effect on the microelectrode performance within the pH range of 7.5 to approximately 8.0. The effect of ionic strength was also investigated. Measurements using this microelectrode were made on activated sludge floc samples taken from a municipal wastewater treatment plant.

Conducting polymer ion sensor electrodes-III. Potentiometric sulfide ion selective electrode.

A new potentiometric sensor electrode for sulfide based on conducting polymer films is introduced. The electrode is formed by electrochemically depositing a film of poly(3-methylthiophene) and poly(dibenzo-18-crown-6) onto an alloy substrate. Different methods were used for the electrode preparations. The alloy used has a low melting point, which allowed its use for manufacturing a microsize version of this electrode. The electrode response is stable for 3 days. The working temperature range for this electrode is between 10 and 40 degrees C. The linear dynamic range is 1.0x10(-7)-1.0x10(-2) M and measures total sulfide concentration over a range of pH from 1 to 13. The polymer electrode showed high selectivity for sulfide in the presence of many common interfering anions. The electrode is useful for the measurement of total sulfide in biological environments and can be manufactured in the micron scale. Therefore, it will be useful for the measurement within biofilms.

Degradation of azo dyes containing aminonaphthol by Sphingomonas sp strain 1CX.

Sphingomonas sp strain 1CX was isolated from a wastewater treatment plant and is capable of aerobically degrading a suite of azo dyes, using them as a sole source of carbon and nitrogen. All azo dyes known to be decolorized by strain 1CX (Orange II, Acid Orange 8, Acid Orange 10, Acid Red 4, and Acid Red 88) have in their structure either 1-amino-2-naphthol or 2-amino-1-naphthol. In addition, an analysis of the structures of the dyes degraded suggests that there are certain positions and types of substituents on the azo dye which determine if degradation will occur. Growth and dye decolorization occurs only aerobically and does not occur under fermentative or denitrification conditions. The mechanism by which 1CX decolorizes azo dyes appears to be through reductive cleavage of the azo bond. In the case of Orange II, the initial degradation products were sulfanilic acid and 1-amino-2-naphthol. Sulfanilic acid, however, was not used by 1CX as a growth substrate. The addition of glucose or inorganic nitrogen inhibited growth and decoloration of azo dyes by 1CX. Attempts to grow the organism on chemically defined media containing several different amino acids and sugars as sources of nitrogen and carbon were not successful. Phylogenetic analysis of Sphingomonas sp strain 1CX shows it to be related to, but distinct from, other azo dye-decolorizing Sphingomonas spp strains isolated previously from the same wastewater treatment facility.

Immobilization of phenol in cement-based solidified/stabilized hazardous wastes using regenerated activated carbon: leaching studies.

In this research, we investigated the use of an inexpensive thermally regenerated activated carbon as a pre-adsorbent in the solidification/stabilization of phenol-contaminated sand. Our results show that even the addition of very low amounts of regenerated activated carbon (1%-2% w/w sand) resulted in the rapid adsorption of phenol in the Chemical solidification/stabilization (S/S) matrix, with phenol leaching reduced by as much as 600%. Adsorption studies indicated that the adsorption of phenol on the reactivated carbon was found to be partially irreversible over time in the S/S waste form, indicating possible chemical adsorption. Pore-fluid analyses of the cement paste containing phenol suggested the formation of a calcium-phenol complex, which further reduced the amount of free phenol present in the pores. Studies using several micro-structural techniques, including field emission scanning electron microscopy, X-ray diffraction, fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy, indicated significant morphological changes in the cement matrix upon the addition of phenol and reactivated carbon. The hydration of cement in the presence of phenol was retarded concomitant with formation of amorphous portlandite.

Immobilization of phenol in cement-based solidified/stabilized hazardous wastes using regenerated activated carbon: role of carbon.

The use of regenerated activated carbon as an immobilizing additive for phenol in solidification/stabilization (S/S) processes was investigated. The adsorption capacity of regenerated carbon was compared to that of the virgin form and was found to be very close. The effects of pH and Ca(OH)(2) concentration within the S/S monolith on the adsorption process were also examined. Kinetic tests were performed to evaluate the adsorption of phenol on different forms of F400 carbon, including the regenerated form. Kinetic tests were performed in aqueous solutions as well as in liquid-sand mixtures. In both cases, it was found that phenol adsorption on F400 carbon was fairly fast. More than 60% of the equilibrium adsorption amount could be achieved within the first hour for aqueous solutions. For sand-solution kinetics, it was found that 1% carbon (based on dry sand weight) was capable of achieving more than 95% removal of the initial amount of phenol present in solution (1000 and 5000 ppm). Fourier transform infrared (FT-IR) spectroscopy and X-ray mapping tests indicated a homogenous mixing of the carbon into the cement matrix. The carbon was also found to enhance the hydration of cement, which was retarded by the existence of phenol.

Stratification and oxidation-reduction potential change in an aerobic and sulfate-reducing biofilm studied using microelectrodes.

Recent studies in aerobic-nitrifying biofilms demonstrated the heterogeneity of biofilms used in wastewater treatment and led to modifications of the homogeneous assumptions in the conventional biofilm kinetic models. However, the stratification in aerobic-anaerobic biofilms has not been well investigated because of a lack of effective experimental tools. In this study a suite of microelectrodes, recently developed in the authors' laboratory, was used to examine the stratification of microbial processes and the change of oxidation-reduction potential (ORP) within an aerobic, sulfate-reducing biofilm. The microelectrodes have tip diameters of 3 to 20 microm and a high spatial resolution. They were used to measure the profiles of oxygen, total dissolved sulfide, ORP, and pH as a function of depth in the biofilm. The biofilm reactor was used to treat an azo-dye-containing wastewater with a chemical oxygen demand of 160 mg/L. The reactor bulk-phase dissolved oxygen concentration of the biofilm was 1.7 mg/L. The experimental results demonstrated that the microbial processes in the biofilm were stratified. In this biofilm, aerobic oxidation took place only in a shallow layer of 0.55 mm near the surface and sulfate reduction occurred in the deeper anoxic zone. The ORP changed with the shift of primary microbial process. The ORP was +362 mV at the biofilm surface and -166 mV near the substratum. Near the interface between the aerobic zone and the sulfate reduction zone, a surprisingly sharp decrease of ORP from a positive potential of +194 mV to a negative potential of -77 mV was observed. This occurred within a narrow band of 50 microm in depth. These new experimental findings support the concept of stratification of microbial processes and the associated ORP change in biofilms.

Decomposition of hazardous organic materials in the solidification/stabilization process using catalytic-activated carbon.

The application of a catalytic-activated carbon to the solidification/stabilization (S/S) process for immobilization of phenol and 2-chlorophenol and catalytic decomposition was investigated. The effect of the catalytic-activated carbon, in amounts of 0.25-1% (by dry sand wt.), on the leaching of phenol and 2-chlorophenol was studied. H2O2 was added as a source of oxygen in the amounts of 1 or 5%, with respect to liquid solution weight. Toxicity characteristic leaching procedure (TCLP) leaching tests showed that adding the catalytic-activated carbon to the S/S matrix significantly reduced the leachability of both phenol and 2-chlorophenol. Only trace amounts of phenol were found in the leaching solution, while the concentration of 2-chlorophenol was below the detection limit of the gas chromatography (GC). Without addition of the catalytic-activated carbon, 87% of the phenol and 92% of the 2-chlorophenol leached. Additional tests on TCLP leachate solutions using GC-mass spectrometry indicated the existence of simple, less hazardous, hydrocarbons, including alcohol. Catalytic-activated carbons treated with phenol in the presence of H2O2 were also analyzed using time of flight-secondary ion mass spectroscopy (TOF-SIMS). Results indicate that the phenol aromatic ring was broken by the catalytic reaction.

Monitoring the influence of toxic compounds on microbial denitrifying biofilm processes.

Microelectrode measurements were conducted to obtain nitrate, pH and redox potential profiles within anoxic denitrifying biofilms. The influence of a toxic organic compound (acid orange 7) on biofilm microprofiles was also monitored using microelectrodes. The data provide evidence that the denitrifying biofilms were stratified into an anoxic layer and an anaerobic layer. The anaerobic zone might provide a niche for the biodegradation of recalcitrant organic compounds in biofilms. It was found that acid orange 7 and its biodegradation byproducts had only a slight impact on biofilm nitrate, pH and redox potential profiles.

Adsorption and biodegradation of azo dye in biofilm processes.

The removal of a common azo dye, acid orange 7 (AO7), in biofilm systems was investigated in this study. The abiotic and biotic fate of AO7 was examined under a variety of operating conditions: aerobic nitrification, anoxic denitrification and anaerobic digestion. A comparison of the performance between biofilm and activated sludge treatment processes was made. The adsorption of AO7 onto biofilm matrix and activated sludge flocs was found to fit the Langmuir equation. However, there is a significant difference in the adsorption capacities between biofilm and activated sludge. AO7 was recalcitrant in both biofilm and activated sludge systems under aerobic conditions. Under anaerobic conditions, AO7 was readily decolorized. AO7 decolorization was also observed under anoxic conditions. However, the presence of nitrate inhibited AO7 decolorization.

In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes.

In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes. Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state. Dissolved oxygen, pH, NH4+, NO3-, and redox potential microelectrodes, with tip diameters ranging from 3-15 microm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms. It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles. The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms. A similar trend was observed for the NO3(-)-N microprofiles. The nitrate production rate decreased as the AO7 concentration in the bulk solution increased. The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited. No significant redox potential differences were observed in the biofilms after AO7 was applied.

Effect of dissolved oxygen concentration on the biofilm and in situ analysis by fluorescence in situ hybridization (FISH) and microelectrodes.

A better understanding of microbiology and ecology of nitrifying bacteria in inner biofilms is an important part of improving process performance and control. Microelectrodes and fluorescent in situ hybridization (FISH) in biofilm research have been used to investigate the spatial distributions of various microbial activities in biofilms and have led to new experimental findings as well as modifications of the homogeneous assumptions in the biofilm kinetic models. The objective of this study is to try the combination of two methods, both FISH and microelectrode measurements, and to provide reliable and in situ information on nitrifying bacterial activity in biofilms. The characteristics of biofilm developed on tygon slides were different according to the change of dissolved oxygen (DO). When the DO increased from 2 to 10 mg DO/L, the rate of the biofilm thickness increased and its dry density changed from 50-70 to 25-90 mg/cm3. Ammonia oxidizing bacteria were not uniformly distributed in biofilm, and were found at the deeper layer where oxygen is depleted, they were detected primarily in the upper and middle layers of the biofilm.

The ACCEND program: a combined BS and MS program in environmental engineering that includes co-operative work experience.

Environmental engineering education has rapidly expanded in recent years and new teaching methods are needed. Many professionals and educators believe that a MS degree in environmental engineering should be the minimum in order to practice the profession, along with practical training. This paper describes an innovative program being offered at the University of Cincinnati that combines an integrated BS in civil engineering and an MS in environmental engineering with extensive practical co-operative education (co-op) experience, all within a five-year period. The program includes distance learning opportunities during the co-op periods. The result is a well-trained graduate who will receive higher pay and more challenging career opportunities, and who will have developed professionalism and maturity beyond that from traditional engineering programs.

Teaching future professors how to teach.

This paper describes a course designed to provide hands-on teaching experience to future professors and to incorporate techniques for more effective teaching. A team of Ph.D. candidates, under the direction of a senior faculty member, prepared a new course from beginning to end and then offered it to a class of graduate students. The course was developed using the unit map concept so that the presentations by the five student-instructors complemented and built upon one another. Immediately after each class, feedback was given to the student-instructors by the faculty advisor and the other student-instructors. Review of video tapes of the lecture reinforced this feedback. At the completion of the course, both students and student-instructors were surveyed as to the effectiveness of the course and the student-instructors. This teaching experience and the feedback obtained from the surveys will be invaluable to the student-instructors in their future development.

Sludge digestion enhancement and nutrient removal from anaerobic supernatant by Mg(OH)2 application.

Anaerobic sludge digestion is a widely adopted process for sludge stabilization. Phosphate removal from anaerobic supernatant is necessary to limit the phosphate returned to the head of the treatment plant, thereby improving the overall treatment efficiency. In this study, magnesium hydroxide (Mg(OH)2) was used to improve the sludge digestion efficiency and to remove phosphorus from anaerobic supernatant. The anaerobic sludge digestion experiment was conducted at a pilot scale, and the results showed that applying Mg(OH)2 to anaerobic sludge digester resulted in a larger reduction in SS and COD, a higher biogas production rate, a lower level of phosphate and ammonia nitrogen concentrations in the sludge supernatant and an improved sludge dewaterability. Research results at both lab scale and pilot scale on phosphorus removal from anaerobic supernatant using Mg(OH)2 showed that a high removal of phosphorus can be achieved through the addition of Mg(OH)2. The required reaction time depends on the initial phosphorus concentration and the Mg(OH)2 dosage.

Evaluation of organics leaching from solidified/stabilized hazardous wastes using a powder reactivated carbon additive.

Cement based stabilization/solidification systems have been widely used to minimize leaching of contaminants from hazardous wastes, particularly for stabilization of wastes that contain heavy metals or other inorganic materials. However, few researchers have demonstrated that stabilization/solidification systems can adequately trap and retain organics present in these wastes. Identification of additives that can be used with the inorganic binder to retain organics has attracted much interest. Activated carbon has been found to be the best additive for immobilizing organic contaminants, but it is generally too expensive for routine use. The use of powdered reactivated carbon was studied in this research to prevent organics from leaching from solidified/stabilized waste forms because it is effective and more economically competitive. The Shrinking Unreacted Core leach test method was employed in this study. Stabilization/solidification waste forms were prepared using five organic compounds--phenol, 2-chlorophenol, chlorobenzene, aniline and Methyl Ethyl Ketone (MEK)--that were spiked into the waste forms at two concentration levels each. Reactivated carbon amounts of 0% (as control), 1% and 2% (w/w) were added into each waste form batch to determine how effectively the reactivated carbon can immobilize those organics and the optimum dose of reactivated carbon addition required. Leachate samples were analyzed using gas chromatography. Results show that 1% reactivated carbon addition is generally enough to reduce leaching of all of the organic contaminants by more than 70%, while a 2% addition reduces leaching for most of the organics to less than 1%.