EMMC process for combined removal of organics, nitrogen and an odor producing substance

In order to improve the process performance regarding the removal of organics, nitrogen, and an odor-causing compound (sulfide) contained in domestic wastewater, an entrapped-mixed-microbial cell (EMMC) with and without humic substances for both fixed and moving carrier reactors and conventional suspended growth culture (i.e. conventional activated sludge process) were investigated simultaneously. Both synthetic (simulated to the organics concentration of general domestic sewage) and actual domestic wastewater were investigated under operational conditions of 12 h of hydraulic retention time (HRT) with 1 h of aeration and 1 h of non-aeration, and 6 h of HRT with continuous aeration, at a room temperature of 25 +/- 2 degrees C. It was found that entrapping humic substances in the EMMC carriers had no impact on the removal of organics, nitrogen, and the odor-producing compound. Additionally, the performance of the EMMC moving carrier system for the removal of these pollutants is similar to that of the EMMC fixed carrier system. In general, the EMMC associated systems which provide high solids retention time achieve a better removal of chemical oxygen demand (COD), nitrogen, and the odor-producing substance than the suspended growth system for both HRTs of 6 h (continuous aeration) and 12 h (1 h of aeration and 1 h of non-aeration). Both the fixed and moving carrier EMMC processes, therefore, have the potential for improvement or replacement of the existing conventional activated sludge process with regard to improving the effluent qualities (such as COD, nitrogen and odor-producing compound) for reuse/disposal.     

Evaluating factors influencing groundwater vulnerability to nitrate pollution: developing the potential of GIS

The 1991 EU Nitrate Directive was designed to reduce water pollution from agriculturally derived nitrates. England and Wales implemented this Directive by controlling agricultural activities within their most vulnerable areas termed Nitrate Vulnerable Zones. These were designated by identifying drinking water catchments (surface and groundwater), at risk from nitrate pollution. However, this method contravened the Nitrate Directive because it only protected drinking water and not all waters. In this paper, a GIS was used to identify all areas of groundwater vulnerable to nitrate pollution. This was achieved by constructing a model containing data on four characteristics: the quality of the water leaving the root zone of a piece of land; soil information; presence of low permeability superficial (drift) material; and aquifer properties. These were combined in a GIS and the various combinations converted into a measure of vulnerability using expert knowledge. Several model variants were produced using different estimates of the quality of the water leaving the root zone and contrasting methods of weighting the input data. When the final models were assessed all produced similar spatial patterns and, when verified by comparison with trend data derived from monitored nitrate concentrations, all the models were statistically significant predictors of groundwater nitrate concentrations. The best predictive model contained a model of nitrate leaching but no land use information, implying that changes in land use will not affect designations based upon this model. The relationship between nitrate levels and borehole intake depths was investigated since there was concern that the observed contrasts in nitrate levels between vulnerability categories might be reflecting differences in borehole intake depths and not actual vulnerability. However, this was not found to be statistically important. Our preferred model provides the basis for developing a new set of groundwater Nitrate Vulnerable Zones that should help England and Wales to comply with the EU Nitrate Directive.     

Importance of Sediment–Water Interactions in Coeur d’Alene Lake,Idaho, USA: Management Implications

A field study at Coeur dAlene Lake, Idaho, USA, was conducted between October 1998 and August 2001 to examine the potential importance of sediment–water interactions on contaminant transport and to provide the first direct measurements of the benthic flux of dissolved solutes of environmental concern in this lake. Because of potential ecological effects, dissolved zinc and orthophosphate were the solutes of primary interest. Results from deployments of an in situ flux chamber indicated that benthic fluxes of dissolved Zn and orthophosphate were comparable in magnitude to riverine inputs. Tracer analyses and benthic-community metrics provided evidence that solute benthic flux were diffusion-controlled at the flux-chamber deployment sites. That is, effects of biomixing (or bioturbation) and ground-water interactions did not strongly influence benthic flux. Remediation efforts in the river might not produce desired water-quality effects in the lake because imposed shifts in concentration gradients near the sediment–water interface would generate a benthic feedback response. Therefore, development of water-quality models to justify remediation strategies requires consideration of contaminant flux between the water column and underlying sediment in basins that have been affected by long-term (decadal) anthropogenic activities.     

Development and Adoption of a Simple Nonpoint Source Pollution Model for Port Phillip Bay,Australia

New computing tools and approaches allow tailored development of software to meet the needs of environmental managers. The processes required for such tailoring fit well with adaptive management concepts where, as knowledge and system understanding develop among managers, the software can be developed or replaced to match. This paper reports on development and adoption of a simple nonpoint source pollution modeling tool, including technical aspects of data support for modeling and social aspects of software design. The software, named FILTER, used a unit load model to generate expected pollutant loads from subcatchments of Port Phillip Bay, Australia. Monitoring data were used for calibration to modify the delivery of generated pollutants to receiving waters. Spatial, tabular, and charting software components were used to provide alternative forms of output visualization. FILTER was developed using a process that resulted in manager-stakeholders taking responsibility for setting of model parameter values and operation of the user interface, thereby encouraging uptake. The inclusive development process, tailoring of the software to manager needs and styles of usage, and matching of model complexity to data and knowledge, resulted in a successful application that has become the current agreed system representation among disparate stakeholder organizations.     

The role of grazing by the lysianassid amphipod<Emphasis Type="Italic"> Orchomenella aahu</Emphasis> in dieback of the kelp<Emphasis Type="Italic"> Ecklonia radiata</Emphasis> in north-eastern New Zealand

The lysianassid amphipod Orchomenella aahu was associated with small-scale mass mortality of Ecklonia radiata, the dominant laminarian alga in north-eastern New Zealand. O. aahu burrowed into and hollowed out stipes with severe bleaching, accelerating mortality by 12–14 months. Meristoderm tissue of bleached plants contained approximately one-third of the phlorotannin content (~4% dry mass) present in unbleached, apparently healthier, sporophytes (~12% dry mass). Unbleached stages consistently lacked amphipod damage. O. aahu also colonised plants when non-lethal storm damage afforded entry into the cortical layers of the primary lamina, and ultimately the stipe. O. aahu typically consumed both medullary and cortical tissue of the stipes, forming networked brood-chambers within them, with increasing populations often reducing the plant to the holdfast. There was synchronised mortality across sites and between depths over spatial scales of metres. Following loss of the mature canopy, recruitment of E. radiata was generally within 2 months at most study sites where mortality had occurred.Communicated by G.F. Humphrey, Sydney     

Repeated trans-Arctic invasions in littoral bivalves: molecular zoogeography of the<Emphasis Type="Italic"> Macoma balthica</Emphasis> complex

From a geographical survey of allozyme variation, a history of repeated trans-Arctic invasions since the Plio-Pleistocene is suggested for circumboreal bivalves of the Macoma balthica complex. A principal genetic subdivision, involving several nearly diagnostic loci and Nei's distance D=0.6, distinguishes the clams of the NE Pacific from those of the NE Atlantic. The Pacific taxon is however also present in Europe, in disjunct isolates in the Baltic Sea and White Sea basins. Nevertheless, these populations have marked Atlantic introgressive elements in their gene pools (ca. 30%). Two further population types are recognized, one in the St. Lawrence estuary, Quebec, the other in Varangerfjorden, NE Norway; the latter appears a mixture of Pacific and Atlantic components in almost equal proportions, in local genetic equilibrium (a hybrid swarm). Populations in temperate North America fall outside the circumboreal M. balthica complex discussed here (D=1.0), and are referred to M. petalum. In a scenario of the history and evolution of the M. balthica complex and the similarly subdivided Mytilus edulis complex, the divergence between Pacific and Atlantic taxa started after an initial introduction of Pacific ancestors to the Atlantic basin, enabled by the Pliocene opening of the Bering Strait. During the Pleistocene and Holocene, the ocean basins were, for the most part, effectively isolated, but occasional re-invasions have taken place, causing secondary contacts of the diverged bivalve types on the Atlantic coasts. The recently re-invaded Pacific taxa in northern Europe now seem to thrive only in the extreme marginal environments. Exact dating of the re-invasions is not possible from current data. Apart from the divergence through isolation, hybridization and introgression have significantly molded the present affinities within the M. balthica complex. A formal taxonomic treatment of reticulate and hybridizing lineages is problematic; yet to recognize the evolutionary and systematic diversity within the M. balthica complex, a subspecies distinction between the NE Atlantic clams and those from the Pacific, Baltic and White Sea basins is suggested.Communicated by L. Hagerman, Helsingør     

Leaching of inorganic contaminants from cement-based waste materials as a result of carbonation during intermittent wetting

Characterization of the leaching behavior of wastes is a crucial step in the environmental assessment for reuse or disposal scenarios. The release of inorganic contaminants from waste materials is typically evaluated by tank leaching of continuously water-saturated material. However, materials, in many field or management scenarios, experience cyclic wetting and drying under varied environmental conditions (i.e. variable relative humidity, atmospheric CO2 or CO2 from biologic activities). During periods of storage in an unsaturated environment, many processes may occur that can influence the release potential and release rate of inorganic constituents. The research presented here was carried out to examine how the phenomena of carbonation during drying influence the release of inorganic contaminants from Portland cement-based materials during cyclic wetting and storage. Batch equilibrium leaching tests were used to determine constituent solubility as a function of pH. Dynamic leaching tests on monolithic material were carried out to determine the rate of constituent release as a function of leaching time and intermittent storage conditions. This paper presents the results observed for three typical waste constituents, arsenic, cadmium and lead.     

The first commercial supercritical water oxidation sludge processing plant

Final disposal of sludge continues to be one of the more pressing problems for the wastewater treatment industry. Present regulations for municipal sludge have favored beneficial use, primarily in land application. However, several agencies and entities have warned of potential health risks associated with these methods. Hydrothermal oxidation provides an alternative method that addresses the health concerns associated with sludge disposal by completely converting all organic matter in the sludge to carbon dioxide, water, and other innocuous materials. A hydrothermal oxidation system using HydroProcessing, L.L.C.'s HydroSolids process has been installed at Harlingen, Texas to process up to 9.8 dry tons per day of sludge. Based on a literature review, this system is the largest hydrothermal oxidation system in the world, and the only one built specifically to process a sludge. Start up of Unit 1 of two units of the HTO system began in April 2001. Early results have indicated COD conversion rates in excess of 99.9%. Harlingen Waterworks System estimates that the HydroSolids system will cost less than other alternatives such as autothermal thermophilic aerobic digestion and more traditional forms of digestion that still require dewatering and final disposal. The Waterworks intends to generate income from the sale of energy in the form of hot water and the use of carbon dioxide from the HydroSolids process for neutralization of high pH industrial effluent. The Waterworks also expects to generate income from the treatment of septage and grease trap wastes.     

Paper mill residuals and compost effects on soil carbon and physical properties

Use of organic by-products as soil amendments in agricultural production exemplifies a strategy for converting wastes to resources. The overall objective of this research was to evaluate the short- and intermediate-term effects of repeatedly amending sandy soil with paper mill residuals (PMR) and composted PMR in a vegetable rotation in Wisconsin's Central Sands. Specifically, we investigated the effects of PMR and composted PMR on total soil C and related these to changes in water-holding capacity and plant-available water (PAW). Amendment effects on irrigation requirements were estimated with a simple soil water balance model. The experimental design was replicated five times as a randomized complete block with four organic amendments: raw PMR, PMR composted alone (PMRC), PMR composted with bark (PMRB), and peat applied at two rates and a non-amended control. All amended treatments significantly increased total soil C relative to the nonamended control following applications in 1998 and 1999. One year following the second serial amendment, all PMR treatments increased PAW by 5 to 45% relative to the control. There was a significant positive linear relationship between total soil C and PAW. All amended treatments reduced the average amount of irrigation water required for potato production by 4 to 30% and the number of irrigation events by 10 to 90%. There was a clear trend of greater reduction in irrigation requirements with more carbon added. The cumulative effects of repeated additions of PMRB suggest that certain composts might sustain elevated PAW and reduce irrigation requirements beyond one year.     

Volatilization and degradation of soil-applied dimethylselenide

Dimethylselenide (DMSe) is a highly volatile gas that is produced by indigenous microorganisms in seleniferous soils and sediments; however, little is known about the soil conditions that affect the persistence of DMSe and its transport to the atmosphere. In this study we investigated the effect of moisture content, temperature, and organic amendments on the degradation of soil-applied DMSe. The degradation of DMSe was entirely a result of biological mechanisms, but changes in temperature (20-40 degrees C) and soil moisture content (30-70% of the maximum water holding capacity) had little influence on the degradation rate. In contrast, amending soil with either 1% casein or gluten (by weight) had an inhibitory effect on the degradation of DMSe. After 18 d, 2.1 times more DMSe was present in the casein-amended soil and 2.6 times more DMSe was present in the gluten-amended soil. The transport of DMSe in packed soil columns was also investigated. Increasing the depth to soil surface was found to significantly decrease the amount of DMSe transported to the air. After 6 d, 57% of DMSe injected 10 cm below the soil surface was volatilized. At an injection depth of 20 cm the cumulative emissions were reduced by 38% and at 30 cm the cumulative emissions were reduced by 51%. In columns containing 1% casein or gluten in the top 5 cm of soil the cumulative loss of DMSe was about 9% higher than in unamended soil. Increasing our understanding of the soil conditions that influence the gaseous diffusion of DMSe should help in determining the feasibility of using Se volatilization as a remediation technique.