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Rion P Merlo R Shane Trussell Slawomir W Hermanowicz David Jenkins 《Water environment research》2007,79(12):2412-2419
The thickening and dewatering of waste activated sludge, from a pilot-scale submerged membrane bioreactor and two bench-scale, complete-mix activated sludge reactors (high-shear and low-shear aeration) treating the same municipal primary effluent, were investigated. Solids settling and compaction were measured using the diluted sludge volume index (DSVI) analysis and a batch centrifugation analysis, respectively. Elevated levels of filamentous microorganisms resulted in higher DSVI values and lower centrifuged pellet concentration. Elevated levels of nocardioform bacteria resulted in lower solids float concentrations, and higher colloidal material reduced solids recovery in batch flotation experiments. Sludge filterability, measured as time-to-filter, was shown to be a function of extracelluar polymeric substances and colloidal material, where higher levels of either reduced sludge filterability. Additional research is necessary to confirm these results using full- or demonstration-scale thickening and dewatering units. 相似文献
73.
The spatial, diel and tidal variability in the abundance of piscivorous fishes and their teleost prey, and the dietary composition
of predatory fishes were investigated in beds of Heterozostera tasmanica within Port Phillip Bay, Australia, from September 1997 to February 1998. Predatory and prey fish assemblages were sampled
from beds of H. tasmanica at three locations during each combination of diel (day and night) and tidal (high and low) cycles. Pelagic and benthic crustaceans
represented >60% by abundance of the diets of all predatory fishes. Seven species, 54% of all predatory fishes, were piscivorous.
These piscivores consumed individuals from seven families, 36.8% of the fish families being associated with seagrass. Western
Australian salmon, Arripis truttacea (Arripidae) (n = 174) and yank flathead, Platycephalus speculator (Platycephalidae) (n = 46) were the most abundant piscivores. A. truttacea consumed larval/post-larval atherinids, gobiids and sillaginids. P. speculator consumed late-juvenile/adult atherinids, clinids and gobiids. While the abundances of piscivores varied between locations
(P < 0.001) and diel periods (P = 0.028), the relative differences in piscivore abundance between sites and diel periods were not consistent between tides.
The abundances of A. truttacea varied in a complex way amongst sites, diel period and tidal cycle, as shown by a three-way interaction between these factors
(P = 0.026). Only during diurnal periods at St. Leonards was the abundance of A. truttacea significantly higher during high than low tides (P < 0.001). During the other diel periods at each site, the abundance of A. truttacea did not vary. P. speculator was significantly more abundant nocturnally (P = 0.017). The abundance of small (prey) fishes varied significantly amongst sites (P < 0.001). During the day, the abundance of small fishes did not vary between high and low tides (P = 0.185), but their nocturnal abundance was greater during low tide (P < 0.001). Atherinids (n = 1732) and sillaginids (n = 1623) were the most abundant families of small fishes. Atherinids were significantly more abundant nocturnally (P = 0.005) and during low tides (P = 0.029), and varied significantly amongst sites (P < 0.001). Sillaginids varied significantly only amongst sites (P < 0.001). Seagrass beds provide a foraging habitat for a diverse assemblage of predatory fishes, many of which are piscivorous.
Anti-predator behaviour and amongst-location variability in abundances of piscivorous fishes may explain some of the diel
and tidal, and broad-scale spatial patterns in small-fish abundances.
Received: 23 July 1999 / Accepted: 18 January 2000 相似文献
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David Jenkins 《Water environment research》2008,80(8):677-687
The development of the tools needed to study the population dynamics of biological wastewater treatment processes is traced from its beginnings in the early 1900s to today's use of molecular biology tools (Oerther and Love, 2003). Examples of the benefits of population dynamics research in improving the performance and aiding the design and operation of biological wastewater treatment processes are given. Some thoughts on future areas of study are presented. 相似文献
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Roger A. Jenkins Ralph H. Ilgner Bruce A. Tomkins Douglas W. Peters 《Journal of the Air & Waste Management Association (1995)》2013,63(2):229-241
Abstract Protocols have been developed and applied for the generation of aerosols that are likely to be comparable to those encountered in field settings for the calibration of easily transportable/portable real-time particle monitors. Aerosols generated were simulated environmental tobacco smoke, cedar wood smoke, cooking oil fumes, and propane stove particles. The time-integrated responses of three nephelometers and a monitor for particle-bound polynuclear aromatic hydrocarbons (PAH) were compared with gravimetric respirable suspended particulate matter (RSP) in a controlled-atmosphere chamber. In general, the monitor responses increased linearly with increasing mass concentration. However, the two monitors that reported mass per volume concentrations tended to overreport the actual RSP concentrations by factors up to 4.4. The real-time PAH monitor did not respond to cooking oil fumes, indicative of little PAH being present in the aerosol. One of the monitors that has been used in a variety of studies reported in the literature (DustTrak) was collocated with gravimetric RSP samplers in several hospitality venues in the Louisville, KY, area. Field studies indicated that the units overreported actual RSP concentrations by factors of 2.6–3.1, depending on whether the sampling was conducted in the nonsmoking or smoking sections of the facilities. 相似文献
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