Dynamic control of a continuous-inflow SBR with time-varying influent loading.

The conventional sequential control of Sequencing Batch Reactor (SBR) is designed with fixed time periods for various operation phases. However, both of the flow rates and qualities of influent vary over time, therefore, a big capacity of wastewater equalization unit is required to cope with influent variability. Such an equalization unit increases the total treatment costs of the system, especially in a small-scale wastewater treatment system. Moreover, in using a SBR treating a time-varying influent loading with conventional sequential control, the system performance cannot be optimized. This paper presents the application of on-line ORP and pH monitoring to dynamically control a continuous-inflow SBR with time-varying loading of influent flow rates and water qualities. Experiential results show that the dynamic controlled SBR revealed not only achieved better substrate removal efficiencies, but also reduced treatment costs.

The feasible sequential control strategy of treating high strength organic nitrogen wastewater with sequencing batch biofilm reactor.

The bio-kinetics and feasible sequential control strategy of treating high strength organic carbon and nitrogen wastewater were investigated by conducting the ABS manufacturing wastewater in a series of Sequencing Batch Biofilm Reactors (SBBRs). The on-line ORP, pH, and DO monitoring parameters were applied to identify the feature-points when ammonification, nitrification, and denitrification ends. The carbonaceous matter removal kinetics in the anaerobic and aerobic reaction stages can be expressed by the Michaelis-Menten equation. High efficiency of organic carbon removal and organic nitrogen ammonification in the anaerobic stage can eliminate the substrate competition and activation inhibition to nitrifying organisms in the following aerobic stage. In the sequencing nitrogen removal processes, the producing time and system ORP values of these feature-points have good function relationships with the influent COD loading rates of SBBR, which can be integrated into a set-point (set-time and set-ORP) sequential control strategy of nitrogen removal. The automatic control operation results revealed ORP was one of the major control parameters of the sequencing nitrogen removal process in SBBR system and high overall removal efficiency were obtained.

Visual function in recovered ethambutol optic neuropathy.

The visual acuity of the patient with ethambutol optic neuropathy will recover within 3 to 4 months after discontinuing the drug. We studied the extent of the recovery of other visual functions. Thirty-six axial type ethambutol optic neuropathy patients, who visited our neuro-ophthalmology clinic from January, 1990, to December, 1993, were included in this study. Fifteen patients (29 eyes) regained their visual acuity to better than 1.0. The average follow-up period following the recovery is 21.7 months. Pattern reversal VEP, Farnsworth-Munsell 100-Hue color vision test, critical flicker frequency (CFF), visual field perimetry, contrast sensitivity and edge-light pupil cycle time were assessed for every affected eye. Latency (P100) of visually evoked potential was delayed in 34.5% (10/29) of eyes. In color vision, 48.3% (14/29) of eyes had deutan or tritan defect. An abnormality of red CFF with value lower than 31 Hz was revealed 51.7% (15/29) eyes. In the visual field, 58.6% (17/29) of eyes had paracentral scotoma, arcuate scotoma, or enlargement of physiologic blind spot. Contrast sensitivity was depressed in 62.1% (18/29) of eyes, mainly at middle and low spatial frequency. Pupil cycle time was prolonged in 72.4% (21/29) of eyes. Aside from visual acuity, other visual functions of the recovered ethambutol optic neuropathy patients were incomplete. The extent of recovery of the visual function is as follows: visual acuity-VEPs-color sense-CFF-visual field-contrast sensitivity-pupil cycle time.