Nitrification of raw or used water using expanded bed biofilm reactor technology.

Excessive ammonia in raw water increases the consumption of chlorine for disinfection during production of potable water, through oxidation to produce chloramines. Excessive ammonia in used water results in pollution of the aquatic environment, where it is particularly toxic to fish. Furthermore, nitrifying prokaryotes in the receiving water will consume dissolved oxygen equivalent to 4.6 g oxygen per g ammonia-nitrogen oxidized to nitrate. This places a considerable oxygen demand on the receiving water and can result in anoxic conditions. One solution to these problems is to nitrify the ammonia in a dedicated biological process. As nitrifiers are particularly slow growing, they are easily washed out of conventional water and wastewater treatment processes; hence, the use of immobilized biomass in an expanded bed biofilm reactor. This solution typically allows at least 10-times the biomass concentration of conventional systems, with a similar decrease in bioreactor size or increase in bioreactor productivity. This chapter describes expanded bed technology for nitrification of water, and methods for studying biomass and process performance.

The expanded bed biofilter: combined nitrification, solids destruction, and removal of bacteria.

Developed for tertiary nitrification, this biofilter also removed carbonaceous BOD (cBOD) and (SS). Because the biofilter is expanded, it cannot clog, and therefore does not require backflushing; yet, it removed a significant proportion of the influent SS. This unanticipated capability was due to the activities of heterotrophic bacteria, protozoa, and metazoa (nematode and oligochaete worms). The expanded bed is an intensified process, which is based on natural immobilization of microbes to small support particles. Using glassy coke as the support material, an attached layer of microbes develops, forming particulate biofilms having a superficial surface area of 1 800 m2 m(-3)(expandedbed). Autotrophic nitritifiers (Nitrosomonas spp.) were detected in the biofilm using rRNA-based molecular methods and were likely responsible, at least in part, for reducing the ammonia concentration by up to 99% (to 0.1 mg L(-1)), while the other organisms reduced cBOD and SS by up to 56% and 62%, respectively. Furthermore, the influent concentrations of Escherichia coli, coliform and heterotrophic bacteria were reduced by over 80%. It thereby provides a single process solution for combined tertiary nitrification and solids removal. Operating the process to consistently achieve < 0.5mg NH3N L(-1) and at the same time removing a significant fraction of cBOD and SS, it can replace processes such as SAFs or NTFs followed by a sandfilter.

Particulate-biofilm, expanded-bed technology for high-rate, low-cost wastewater treatment: nitrification.

The performance of a particulate-biofilm, expanded-bed process for nitrification of activated sludge final effluent (ASFE) is reported for a plant receiving mixed industrial and domestic wastewater. The support material for the particulate-biofilms was glassy coke, to which the nitrifying bacteria attached and formed a highly active biofilm. An average nitrification rate of 1.7+/-0.6 kg m(expanded bed)(-3)d(-1) was recorded during operation of the bioreactor, which had a hydraulic residence time of 15 min. On average, the ASFE contained 12.6+/-3.7 g m(-3) NH3-N, which was reduced to 2.6+/-3.3 g m(-3) NH3-N. Furthermore, transfer of 10-12% of the oxygen in air was achieved using counter-current aeration. This investigation has demonstrated that a high rate of nitrification can be achieved with a particulate-biofilm, expanded-bed process. It has also demonstrated that the process can operate without backwashing and still remove particulate material from the ASFE feed.

Continuous affinity-based selection: rapid screening and simultaneous amplification of bacterial surface-display libraries.

A new method for continuous biopanning has been developed. We have combined the power of affinity chromatography with the fecundity of bacteria in a unique process that mimics clonal selection. Mixed populations of bacteria were applied to a fermenter containing the immobilized ligand of interest. Bacteria retained in this affinity fermenter were allowed to grow under continuous washout conditions, such that weakly bound organisms were selectively lost. Those initially rare founder bacteria expressing a receptor for the immobilized ligand (R+ve) were thus enriched and amplified simultaneously. From an initial culture containing 1 x 10(10) R-ve cells spiked with fewer than 30 R+ve bacteria (<1 in 10(8)), final ratios of R+ve/R-ve bacteria as high as 1 in 12 were observed, representing an enrichment factor of 55 million-fold. This technology has considerable potential for rapid screening of bacterial surface-display libraries and in facilitating directed-evolution studies.

Report on the clinical workstation and clinical data repository utilization at UNC Hospitals.

On December 1, 1993, we implemented version 2.1 of the Clinical Workstation-Clinical Data Repository application in the Ambulatory Care Center. This version of the workstation allowed access of laboratory data from the clinical data repository that had been populated by a real-time HL7 interface between the Clinical Data Repository and the Laboratory Information System. This implementation completed a major part of the Clinical Workstation project. Also in December, we implemented a security system that records the date and time, user logon code, clinical workstation functions used, and the patient medical record number on whom data were displayed. In addition to the security function, this system has proven to be a valuable tool in evaluating the utilization of the clinical workstation and is the source of the data presented in this paper.

Progress report on the clinical workstation and clinical data repository at UNC Hospitals.

In 1991, we demonstrated a prototype version of the Clinical Workstation at SCAMC. At the present time 48 workstations have been implemented in the ambulatory care areas of the Hospital. We describe the present functionality of the workstation and the work done to date on the clinical data repository.

Temperature and potency of d-tubocurarine and pancuronium in vitro.

The concentrations of d-tubocurarine and pancuronium producing 50% block of the indirectly elicited twitch were determined in isolated mouse nerve-diaphragm preparations at 37 and 25 C. The contralateral side was used as a control in a 2 x 2 factorial analysis of variance. Cooling shifted the dose-response curves for both drugs to the left, but only slightly (from 1.69 +/- 0.022 microM to 1.49 +/- 0.021 microM with d-tubocurarine and from 0.65 +/- 0.012 microM to 0.46 +/- 0.009 microM with pancuronium). The dose-response relationship was, however, so steep (Hill coefficient approximately 5 to 6) that a slight horizontal shift of the dose-response curve corresponds to a considerable decrease in the twitch response at a concentration midway between the curves. Thus, studies using only the concentration that produces partial block of twitch responses misleadingly suggest a large effect of temperature. Similarly, if in another system the curve were to shift to the right even only slightly, a temperature effect in the reverse direction might be reported. It is concluded that temperature appears to have little influence on cellular potency of neuromuscular blocking agents.

Toxicity and mutagenicity of radiation from fluorescent lamps and a sunlamp in L5178y mouse lymphoma cells.

Unfiltered broad spectrum radiation emitted by black light, cool white, and black light blue fluorescent lamps and a sunlamp, is both toxic and mutagenic to L5178Y mouse lymphoma cells when the cells are irradiated in phosphate-buffered saline. The increase in mutant frequency seen after exposure of the cells is linear throughout the range of exposures tested. The linear increase in mutagenesis is observed even at exposure levels which do not cause significant toxicity. To facilitate comparison of the differing rates of mutagenesis derived from exposure-response curves obtained for each light source, we have defined a parameter, joule-equivalent mutagenesis (jem), equal to mutants per 10(5) survivors per joule per square meter. Jem values are calculated using the integrated irradiance of each lamp. Based on jem values, the relative mutagenicity of the various lamps tested (compared with a germicidal ultraviolet lamp) is 3 x 10(-3) for the sunlamp, 1 x 10(-4) for the black light and cool white lamps, and 3 x 10(-5) for the black light blue lamp. The toxic and mutagenic effects of the lamps are in reasonable agreement with their relative spectral output from 290 to 330 nm.

Saskatchewan dial-access drug information service.

In September 1974 the colleges of pharmacy and medicine of the University of Saskatchewan began offering a drug information service to the pharmacists and physicians of Saskatchewan without charge. With the help of a radio-page system, calls are taken immediately by experienced pharmacists and pharmacologists. The cost of long-distance phone calls is borne by grants from the Saskatchewan medical and pharmaceutical associations. During the 1st year of operation 415 requests for information were received. Of 93 persons who called up to Feb. 28, 1975, 76% responded to an evaluation questionnaire; virtually all described the service as very valuable. The information received resulted in the alteration of drug therapy in one third of calls requesting information to assist in current treatment of a patient.