There was a selective deficit for global motion processing that was not due to the visibility of the stimuli and was nonselective for spatial scale. The eye with the more complete recovery (acuity 20/20) from pattern deprivation in childhood exhibited the more severe global motion deficit. discussion. The results suggest a primary extrastriate deficit in the dorsal pathway, possibly involving the middle temporal (MT) and the medial superior temporal (MST) cortical areas, that is unrelated to the acuity deficit thought to be in area V1. A similar deficit has recently been shown in strabismic amblyopia.

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA A model for nitrification in a coupled trickling filter/ activated sludge system is presented. Nitrification will occur in the trickling filter component of the system when the organic loading to the trickling filter is about 1 kg BOD 5 /m 3 .d(60 lb BOD 5 /1 000 ft 3 -day) the degree of nitrification will increase as the organic loading decreases below this value. Nitrification in the upstream trickling filter has two impacts on the downstream suspended growth unit. First, partial removal of ammonia by the upstream trickling filter reduces the ammonia-nitrogen loading on the downstream suspended growth unit. Second, the seeding effect of nitrifiers grown on the upstream trickling filter which slough off and pass into the downstream suspended growth unit allows the suspended growth unit to nitrify at solids residence times that would otherwise preclude nitrification. A mathematical model for the suspended growth units that incorporates this seeding effect is developed and presented. Data from the City of Garland, Texas, Duck Creek and Rowlett Creek Wastewater Treatment Plants are presented that demonstrate this mechanism and verify the predictive capability of the proposed model. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res., 65, 750 (1993).

Long-term data from three full-scale trickling filters installations accomplishing combined carbon oxidation and nitrification are presented. Analysis of these data indicates that the oxidation of organic matter and ammonia-nitrogen in the trickling filter can be characterized by a single parameter which is calculated as the trickling filter organic loading (expressed in terms of BOD5 or biodegradable COD) plus the ammonia-nitrogen oxidized converted to oxygen equivalents using the conversion factor 4.6 kgO2/kg NO3-N. This parameter, which is referred to as the volumetric oxidation rate and is expressed in the units of kgO2/m3-day, characterizes trickling filter performance over a wide range of process loading and effluent quality conditions. The method of analysis presented in this work differs from the one traditionally used to characterize combined carbon oxidation and nitrification in trickling filters, and its suggests that oxidation may be oxygen transfer limited throughout such a trickling filter.

CLOSURE and nitrification must occur to some extent. In our mind, the only question is how reliable is this mechanism, that is, are nitrifiers sloughed on a relatively consistent basis? To answer this question, we believe that the term "consistent" must be defined on an operational rather than a theoretical basis. That is, do models derived based on this assumption possess sufficient predictive capability to be useful? That is the approach used in this research and is the reason for presenting the Duck Creek and Rowlett Creek data, which indicate that models derived on this basis are useful.The discussors request presentation of the NR data from the Duck Creek plant. We thank them for this in that these data were present in the version of the paper originally submitted to WEF, but they were taken out of the paper in response to review comments. Figure A of this discussion presents the NR data for Duck Creek, which demonstrate that the NR based on the contact basin only was consistently less than 1.0 and that the NR based on the entire suspended growth reactor was also frequently less than 1.0. These results indicate that nitrification would not have occurred in the suspended growth reactor at Duck Creek if nitrifiers were not being seeded into it from the upstream trickling filter. These results demonstrate the utility of the model and support its underlying assumptions from an operational perspective.The discussors also ask whether the authors are aware of any further data supporting the proposed hypothesis. A complete response to this question would be an entire technical paper by itself. Since the original version of the paper was prepared and originally presented at the WEF Conference in Washington D.C., the authors have been made aware of observations by others that are similar to the Duck Creek and Rowlett Creek wastewater treatment plants. For example, a pilot plant at Windsor, Ontario, Canada has clearly demonstrated nitrification in a TF/SC facility at conditions that were not achievable in a companion activated sludge process (that is, one without an upstream trickling filter accomplishing combined carbon oxidation and nitrification).The authors thank the discussors for their thoughtful comments on our work. In this closure we will respond directly to the four questions that they have asked. This closure also provides the opportunity to correct a typographical error contained in the original paper. That error is in Equation (8) which, unfortunately is the critical equation of the paper. The error is in the second term of the equation and involves a minus sign which was omitted. The correct equation is listed below.To Discussion of: Process and kinetic analysis of nitrification in coupled trickling filter/activated sludge systems, 65, 750 (1993); Discussion by D. S. Parker, J. T. Richards, 66, 934 (1994).In their introduction the discussors indicate that they used the IAWPRC activated sludge model, with seeding, to analyze the first months of operation of the Duck Creek TF/SC plant. The authors point...

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