The starch manufacturing industrial units, such as sago mills,both in medium and large scale, suffer from inadequate treatment and disposal problems due to high concentration of suspended solids present in the sludge. A laboratory scale study was conducted to investigate the viability of anaerobic treatment of sago waste sludge, enriched in particulate organicmatter, using a fluidized bed reactor. The start-up of the reactor was carried out using a mixture of digested supernatantsewage sludge and cow dung slurry in different proportions. The effect of operating variables such as COD of the effluent, bed expansion, minimum fluidization velocity on efficiency oftreatment and recovery of biogas was investigated. The maximum efficiency of treatment was found to be 82% and the nitrogen enriched digested sludge was recommended for agricultural use. A kinetic model was developed for the degradation of particulate organic matter using the general kinetic equation [dS/dt = K HC SXC] which allowed for a more accurate mathematical representation of the hydrolysis process. Analysing data from a series of batch tests, the best fit value of C was found to be in the range 0.43 to 0.62.

Using ¹³C/¹²C ratios in particulate organic carbon(POC), this study evaluated the fraction of terrestrially derivedPOC in Winyah Bay, South Carolina, an anthropogenically impactedestuary in the southeastern United States. Results from themixing model, which should be viewed as an upper limit becauseof possible dilution from additional potential end-members,showed that between 50 and 90% of POC in the Winyah Bay estuaryis of terrestrial origin. As this POC may be associated withriver-transported pollutants, the potential for accumulation ofpollutants in Winyah Bay is high because POC may become trappedin the estuary as part of either estuarine bottom sediments,circulation or food webs. Thus strategies for pollutionmonitoring and control in the estuary and its watershed arenecessary for the future management of Winyah Bay naturalresources.

The incentives and approaches for modelling chemical fate at a continental scale are discussed and reviewed. It is suggested that a multi-media model consisting of some 20–30 regions, each of which contains typically seven environmental compartments represents a reasonable compromise between the issues of the need for detailed resolution, avoidance of excessive data demands and inherent complexity and transparency. Strategies adopted in compiling the Berkley-Trent (BETR) model for North America are discussed and used to illustrate the issues of selecting appropriate number and nature of segments, treatment of air and water flows and the acquisition of environmental data. It is suggested that GIS software can play a valuable role in gathering and processing such data and in the display and interpretation of the results of the model assessment. The BETR model will be a useful tool for describing the nature of persistence and long-range transport of chemicals of concern in the North American environment.

Results from the photolysis ofo, p-dichlorobenzene, bromobenzene, andp-dibromobenzene in water ice are reported. All phototransformations appeared to be based on dehalogenation, coupling, and rearrangement reactions in ice cavities. No photosolvolysis products, i.e. products from intermolecular reactions between organic and water molecules, were found. Many of the products were very toxic substances of a high environmental risk, such as PCBs. The results support our model, in which secondary, very toxic, pollutants can be formed in ice, snow, and atmospheric ice particles from primary pollutants through the action of solar irradiation. The photoproducts may be released to the environment by ice melting and evaporation.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.