Effects of an external magnetic field on the sedimentation of activated sludge

By applying an external magnetic field (800–3000 G, 0.08–0.30 T) using permanent magnets to the aeration vessel of an activated sludge culture, the sedimentation of activated sludge was enhanced and chemical oxygen demand (COD) removal was also improved in an indoor continuous culture system. Adding a small amount of iron(III) chloride (FeCl₃, less than 0.1%, w/v) stimulated these enhancements. The possibility was suggested that the small amount of molecular iron incorporated into the activated sludge stimulated the flocculation and sedimentation by external magnetization.     

The fish populations of an industrial river in South Wales

The River Sirhowy, a trout river of the Ebbw System in south-east Wales still subject to sporadically high levels of suspended solids derived from the coal mining industry, was investigated over a three year period to assess its importance in the recolonization of a fishless river, the Ebbw Fawr, which is expected to recover from the effects of steelworks effluents discharged near its headwaters. Eight species of fish were recorded. Spawning areas for brown trout ( Salmo trutta L.) were limited by industrial and urban developments and the discharge of suspended solids. Small numbers of native trout were produced in the system and the growth of these fish was poor in the main river, confirming the need for regular stocking. Movements of stocked trout were limited except in the lower reaches of the river where the presence of a native population, high levels of suspended solids and flash floods may have increased the numbers of fish moving into the recovering Ebbw Fawr.     

Morphological controls on medium-term sedimentation rates on British lowland river floodplains

This paper outlines a novel two-stage procedure for estimating medium-term (ca. 40 years) rates of overbank sedimentation on British lowland floodplains, and exploring the relationship between floodplain morphology, floodwater hydraulics and fine sediment storage. The first stage utilises a two-dimensional hydraulic model that solves the depth-averaged shallow water equations over a high resolution topographic grid. This model is used to predict distributed patterns of flow depth and velocity within floodplain reaches approximately 0.4–0.6 km in length for floods of varying magnitude. These hydraulic data are then used, in conjunction with a simple sediment transport and deposition model, to estimate rates and patterns of floodplain sedimentation. This procedure was applied to a series of eight sites on the floodplain of the River Culm, Devon, UK, with contrasting morphological characteristics (e.g., channel sinuosity, channel numbers and dimensions, bankfull discharge, floodplain width, etc). The hydraulic modelling procedure was validated using ground and oblique aerial photography of floodwater inundation patterns. Estimates of medium-term sedimentation derived from ¹³⁷Cs analysis of floodplain sediment cores were used to calibrate the sediment deposition model. Results indicate that within-reach variability in sedimentation rates reflects small-scale topographic controls on local flow characteristics and sediment transport and deposition processes. In contrast, between-reach variations in total sediment storage are largely a product of downstream changes in gross valley floor morphology and flood frequency. Preliminary estimates of the total sediment flux to the floodplain of the River Culm for the basin as a whole are consistent with previous estimates and highlight the importance of floodplain sedimentation as a component of the overall catchment sediment budget.     

Particulate phosphorus sedimentation at the river inflow to a lake

Sedimentation at the Krutynia River inflow to Lake Kujno was closely related to hydrological regime. The highest sedimentation rates, recorded in spring, decreased during summer by two orders of magnitude. Granulometric segregation of settling seston along the inflow zone was related to differentiation of phoshorus content. Smaller particles were richer in P, producing a gradient of increasing P concentrations in the settling material. A substantial loss of P from polyphosphate and various organic fractions was found after settlement of river suspensoids. Mechanisms of P losses are discussed and possibilities of P retention within the inflow zone are considered.     

Effects of an external magnetic field on the flock size and sedimentation of activated sludge

Effects of an external magnetic field on sedimentation enhancement were investigated using three kinds of practical activated sludge. An indoor experiment was setup (3.5l aeration vessel) equipped with a broth circulation system and 800 G of external magnetic field. The application of an external magnetic field to the activated sludge enhanced the sedimentation irrespective of the nature of the activated sludge. At the same time, the flock size of the sludge was enlarged by the external magnetic field. However, the surface zeta potentials of the sludge were not changed by the external magnetic field. Addition of FeCl₃ to the sludge enhanced the effects of the external magnetic field. Based on these results, the following mechanism for the enhancement of sedimentation by the external magnetic field is suggested: activated sludge containing iron was magnetized during entry to the magnetic field and coagulated with the magnetic force. As a consequence, the flock size was enlarged. Almost the same sedimentation enhancement by external magnetization was confirmed by a pilot scale magnetization system (2.0 m³ of aeration vessel) when the airlift type of mild broth circulation system was equipped with a 5000 G magnetic field.     

Issues in the development of an industrial bioprocess advisory system

The background and motivation for the construction of a fault detection and advisory system for an industrial fermentation process plant are described. Here, the knowledge extracted from the operators (implemented in the form of production rules) is integrated with multivariate data-based methods for fault detection. The industrial benefits arising from this integrated system include: (1) reduced variability, (2) increased mean performance levels, (3) reduced operator-training time and (4) knowledge management in the broader organization.     

Effects of sedimentation on settlement of Acropora millepora

Sedimentation is assumed to affect communities of reef-building corals by inhibiting larval settlement, however there has been no quantitative evidence to support this supposition. The effects of varying rates of sedimentation (0.5 to 325 mg cm^-2d^-1) on settlement rates of Acropora millepora larvae were examined experimentally, in aquaria. Settlement and juvenile orientation onto conditioned cut coral plates were recorded after two days. Higher sedimentation rates reduced the number of larvae settling on uppersurfaces, but total numbers of settled larvae were not significantly affected by sedimentary regime. While total settlement was unaffected by sediment under the confined experimental conditions, it is likely to be reduced under field conditions, since accumulation of sediment on upward-facing surfaces will greatly reduce the overall amount of suitable substratum available.     

Hydrobiological studies on the Tugela river system

Summary A chemical and biological survey of the Tugela river, Natal is described. Some relationships between physical and chemical conditions in the river and the geology and climate of the basin are indicated. The flora and fauna of the main river is described, and the zonation of species in the river, and seasonal variations in the communities at various stations in the zones are delineated.Some relationships between the physical and chemical conditions in the basin, and the distribution and seasonal variations of the biological communities are indicated. Comparisons are made with other rivers. It is concluded that the Tugela river as a type in Southern Africa, falls intermediate between temperate and sub-tropical conditions.     

Effects of inorganic sedimentation and riparian clearing on benthic community metabolism in an agriculturally-disturbed stream

An in situ chamber technique was used to obtain seasonal estimates of benthic community metabolism at three stations in an agriculturally disturbed stream. Two stations with open canopies were examined. Sand was the dominant substrate at one site, cobble at the other. The third station was shaded by riparian vegetation and had a sand substrate.Seasonal estimates of net community productivity (NCP) and community respiration (CR) at the cobble section were significantly higher than those calculated for the sand sections (p>0.05). Ratios of gross community productivity (GCP) to 24 h respiration indicated autotrophic conditions in the cobble and extreme heterotrophy in the sand. NCP was significantly higher (p<0.05) in the open canopy sand than in the riparian shaded sand only when turbidity and discharge were low. Measurements of periphyton ash-free dry mass (AFDM) and chlorophyll a support metabolism estimates. Measurements of loose detrital AFDM were very low and variable compared to others reported in the literature. Therefore, allochthonously derived detritus may not be an important energy source for the benthic community.     

The influence of land use on the sedimentation of the river delta in the Kyrönjoki drainage basin

Sediment surface samples (0–2 cm) from 66 sites, and longer cores (up to 540 cm) from 9 sites in the estuary of the river Kyrönjoki, Western Finland, were analysed for organic content, P, Fe, Mn, Pb, Cd, Cu and Zn. One core was dated on the basis of annual laminations.Chemical analyses of the cores showed that organic matter and heavy metal content have increased in recent decades. The heavy metal content was clearly lower than in areas polluted by industry. The sedimentation rate in the delta increased between the 1930s and 1950. It decreased in the 1960s, and has been below 1930s levels since 1970. The sedimentation rates of organic matter were fairly stable all through the period measured, even though the organic content increased.The increase in organic matter and the heavy metal content of the sediment in recent decades is evidently due to the increased intensity of agriculture, forestry and peat harvesting in the drainage basin. Drainage of peatlands in particular has increased erosion and the organic sediment load of the river. Reservoir building after 1970 has decreased the sedimentation rates in the delta.     

Studies on the Ephemeroptera of a Northumbrian river system

The River Coquet is a clean, fast flowing, moderately calcareous river. It is young to mature in development and supports a typical torrential fauna. Marked trends in successional replacement along the river course are confined to the scarce species of Ephemeroptera and the absence of longitudinal zonation in the distribution of some common species is related to the topographical characteristics of the system. A distinct successional trend by one species is attributed to its intolerance to the lower temperatures at high altitudes. Major discontinuities in distribution are found between the Ephemeroptera of the main river and certain tributaries. The paucity of certain otherwise abundant species in one region is related to silt deposition resulting from sand and gravel excavation.     

Effects of contrast media on erythrocyte aggregation during sedimentation

To evaluate the effects of contrast media (CMs) on erythrocyte aggregation, we measured the erythrocyte sedimentation with Westergren method at 25 degrees C. CMs were diatrizoate (Urografin 76%) for ionic CM and iopamidol (Iopamiron 370) for nonionic CM. Swine red blood cells (RBCs) were suspended in autologous plasma containing diatrizoate (URO), iopamidol (IOP), and saline (SAL) at 6.7% w/w, as well as in plasma alone (PLA), at 40% of the hematocrit. Sigmoid sedimentation curves were fitted to the Puccini et al. (1977) equation, and the average number of RBCs per aggregate m was calculated by Stokes' law against the time t. According to the Murata-Secomb (1988) theory we estimated the collision rate K between two aggregates from dm/dt in the stationary phase during sedimentation. Corresponding to the maximal ESR, the dm/dt (in cells/s) was 0.52 in PLA, 0.09 in SAL, 0.06 in URO and 0.03 in IOP, so that K also decreased in proportion to dm/dt from 145 fL/s in PLA to 8 fL/s in IOP. Both the ionic and nonionic CMs tend to inhibit the RBC aggregation more than that in SAL; the latter iopamidol appears to be inhibitory more than the former diatrizoate in autologous plasma.     

Effects of sedimentation on the storage capacity of the High Aswan Dam reservoir

The River Nile receives most of its sediment load from the Atbara and Blue Nile rivers, which carry eroded sediments north from the Ethiopian mountains during the seasonal flood period between August and October. Prior to the construction and operation of the High Aswan Dam, in 1964, 9–10 × 10⁶ metric tons of suspended sediment were deposited annually in the flood plain of the Nile, while about 93% of the total average annual suspended load of 124 × 10⁶ metric tons was carried out into the Mediterranean Sea. Since the full operation of the High Aswan Dam in 1968, the flood discharge of the Nile, below the dam, has been greatly modified and more than 98% of the total suspended load has been retained within the reservoir. Based on long-term records; estimated relationships between discharge and suspended load, and field measurements, the life span of the dead storage capacity has been estimated at a minimum of about 360 years. Although this preliminary calculation is less than the estimated design capacity of 450 years, it is expected that progressively more suspended solids will be released in the outflow of the reservoir and that together with the use of flood diversion schemes the High Aswan Dam is likely to approach its design life span.