No description available.

The availability of phosphorus from the anoxic hypolimnia of lakes to epilimnetic plankton was investigated by experimental studies on eight lakes in Ontario and Quebec. Availability was determined with a short-term bioassay based on the standardized retardation of planktonic uptake of phosphorus tracer in the presence of orthophosphate; availability was also estimated by SRP (soluble reactive phosphorus) analysis, since approximately 90% of SRP was available in anoxic waters. / Iron concentrations were high in some hypolimnia, but should become diluted after mixing with surface water. When iron concentrations after mixing exceeded 0.20 mg/L, aeration lowered availability and SRP. Therefore, samples from anoxic hypolimnia were kept anoxic. The fate of hypolimnetic phosphorus at turnover was studied by construction of a budget for SRP, total phosphorus, particulate iron containing phosphorus and particulate biological phosphorus at fall turnover in Lake Magog. Despite high concentrations of hypolimnetic iron, only 30% of the upwelling hypolimnetic phosphorus combined with iron after complete mixing, 30% was incorporated into biomass and 38% stayed potentially available as SRP. / In two lakes, hypolimnetic iron was undetectable hydrogen sulfide concentrations were high. H(,2)S interfered with the SRP analysis and poisoned plankton. After degassing, routine SRP analysis was possible, and availability was close to 100%. Iron and H(,2)S interference in the SRP analysis were circumvented by degassing or by maintaining anoxia. A simpler method, the analysis of TRP (total reactive phosphorus) after aeration, was developed which analyses SRP quantitatively in anoxic waters.

Interspecific competition for phosphorus was studied in continuous lake water cultures of phytoplankton communities from Lake Memphremagog, and its outcome shown to depend primarily on the size of the competitors. Comparison of the activity of the inducible enzyme alkaline phosphatase between the lake and cultures operated at various dilution rates (0.06-0.93 day('-1)) established that in situ phosphorus limitation rarely depressed average community growth rates much below 0.6 day('-1). Growth rates under comparable, or even more severe (0.2-0.3 day('-1)) limitation in culture decreased significantly with increasing cell size. Phosphorus uptake kinetics and cell quotas measured by track autoradiography on the competing species showed that biomass and quota-specific uptake rates varied inversely with cell size in highly significant allometric regressions, correctly predicting that competitive outcome should depend on size. Substituted in a variable internal stores model of phosphorus limited growth, the allometric functions for uptake, cell quota, and maximum growth rate correctly predicted observed growth rates except in competition much stronger than natural (D = 0.06-0.2 day('-1)). Failure of the model to encompass cell senescence and death due to severe nutrient stress appeared to account for the discrepancy. Neither the absolute difference in growth rates due to cell size nor the direction of selection among the naturally co-occurring species varied systematically with the intensity of competition, indicating that spatio-temporal variation of limiting phosphorus supply in nature is unlikely to directly select the size or taxonomic composition of phytoplankton communities.

No description available.

The objective of the research program was to demonstrate the technical feasibility of removing phosphorus, by the enhanced biological phosphorus removal mechanism, from domestic wastewater using a laboratory scale Sequencing Batch Rotating Biological Contactor (SBRBC). The rotating discs of the RBC were subjected to alternating anaerobic/aerobic conditions by varying the water level in the reaction vessel. At the start of the treatment cycle, the RBC reactor would be filled submerging the rotating discs and ensuring anaerobic conditions in the RBC biofilm. Acetate would be added to the reaction vessel at this time. Following the batch anaerobic react period part of the reactor contents were decanted to either the sewage feed tank or a separate holding vessel to later become part of the influent for the next treatment cycle. With the rotating: discs of the-RBC partially submerged oxygen was available to the bacteria, in the RBC biofilm. Three operating schedules were tried with the above process. Each operating schedule differed in the way the decanted wastewater from the anaerobic phase was handled. Batch tests were conducted weekly to determine the nature of the biological reactions taking place in each of the batch anaerobic and aerobic phases. The SBRBC process showed promise for enhanced biological phosphorus removal from domestic wastewater. Carbon removal and nitrification of the wastewater were secondary benefits to this process. The success of the process was found to be dependent on the attainment of proper anaerobic conditions at the start of each treatment cycle. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

No description available.

No description available.

No description available.

No description available.

Graduation date: 1993