Deep Outfall Research Articles

Modeling and experimental research of turbulent jet propagation in the stratified environment of coastal water areas

The results of model calculations and experimental research of turbulent jet propagation in a stratified environment with reference to the Sand Island wastewater outfall (Hawaii) are considered. The jet’s emergence and initial dilution were estimated on the basis of model calculations and experimental data of the stratified environment characteristics in 2003–2004. The reason for the appearance of the bidirectional quasi-isopycnic structure in the waste and ocean water mixing area was clarified, and an analysis of the TS index was carried out. The jet’s features as calculated from the model and obtained from measurements with hydrophysical and hydrooptical instrumentation were found to closely correspond. The effects of the tides and hydrophysical conditions on the waste water’s turbulent jet characteristics (the jet’s floating-up depth level) have been revealed. The outcomes of the study corroborate the efficiency of the model as a tool for research of deep outfall turbulent jet propagation in the stratified environment of coastal water areas.

Water Management Aspects of the Britannia Mine Remediation Project, British Columbia, Canada

The Province of British Columbia, Canada, is undertaking environmental remediation at Britannia Mine, located approximately 45 km north of Vancouver. Britannia Mine operated for 70 years and produced mainly copper and zinc concentrates. During its operating life, and since its closure in 1974, the mine has discharged large volumes of acidic water with elevated concentrations of potentially toxic metals, including copper, zinc, and cadmium. Prior to the recent remedial efforts, metal loadings to Howe Sound averaged 300 kg/day each of copper and zinc. In addition to the acid rock drainage, mine infrastructure and mineral processing activities provide secondary sources of metal contamination of soils, sediments, ground water, and surface water. Effective water management is key to the remedial plan for the mine: ground water and surface water are the primary transport pathways for the metal contamination reaching the local receptors of Britannia and Furry creeks, and Howe Sound. The remedial concept includes diversion of clean water from entering the mine, use of the mine workings as a storage reservoir to balance seasonal flows to a water treatment plant, prior to discharging to Howe Sound via a deep outfall, and the interception of a metal-contaminated ground water plume.

Minor improvement for intertidal seaweeds and invertebrates after acid mine drainage diversion at Britannia Beach, Pacific Canada

In December 2001, acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (British Columbia, Canada) was diverted to flow from Britannia Creek into an outfall at 30 m depth in Howe Sound. Britannia Beach was studied in early 2003 to determine whether AMD diversion resulted in improved conditions for intertidal organisms. Species number and abundance have increased at the intertidal zone since AMD diversion, although they were still lower than at an unpolluted control site nearby (Furry Creek). Survivorship and growth rates of transplanted Mytilus trossulus (mussel) have increased since AMD diversion, although they were still significantly lower than at the control site. Transplanted Fucus gardneri (seaweed) performed better than before the AMD diversion; at Britannia Beach the chlorophyll a concentration in tissues was not significantly different from that at the control site, although the concentration of chlorophyll c in tissues and the chlorophyll c to a ratio was lower than at the control site six weeks after transplantation. Britannia Beach is still subject to leaching of metals from surrounding soils, low levels of AMD coming down the creek, and AMD discharge from the deep outfall. Although there has been an improvement, the intertidal environment at Britannia Beach still seems unable to support normal growth and survival of organisms.

The effects of untreated municipal sewage discharge to the marine environment off Victoria, British Columbia, Canada

The Victoria area (British Columbia, Canada) discharges screened wastewater through two long deep outfalls (Macaulay and Clover Point) into an oceanic environment characterized by strong turbulent tidal flows. Monitoring of the receiving waters has indicated that conventional water quality parameters have not been affected by the discharges. Fecal coliform levels above the outfalls are periodically elevated but remain well below the swimming standard. Shoreline studies of fecal coliform levels have shown that the deep outfalls have not measurably affected water quality at beaches. Recently, monitoring efforts have concentrated on effects to the seafloor environment. At Macaulay Point, sediment chemical levels of concern were confined to within 100 to 400 m of the outfall. Similarly, sediment toxicity was detected at stations up to 400 m from the diffusers. This toxicity was limited to effects on growth and development. Survival was not affected. The benthic infaunal community exhibited a typical response to organic enrichment. Within 100 m of the outfall abundance was increased and richness depressed. At Clover Point sediment chemical levels of concern were confined to within 100 to 200 m of the outfall. Tissue chemistry of resident mussels showed no consistent pattern with distance from the outfall. Some tissue chemicals increased with distance from the diffuser while others decreased. Overall the impact of the outfalls on the seafloor was found to be minimal and restricted in extent.

The effects of untreated municipal sewage discharge to the marine environment off Victoria, British Columbia, Canada

The Victoria area (British Columbia, Canada) discharges screened wastewater through two long deep outfalls (Macaulay and Clover Point) into an oceanic environment characterized by strong turbulent tidal flows. Monitoring of the receiving waters has indicated that conventional water quality parameters have not been affected by the discharges. Fecal coliform levels above the outfalls are periodically elevated but remain well below the swimming standard. Shoreline studies of fecal coliform levels have shown that the deep outfalls have not measurably affected water quality at beaches. Recently, monitoring efforts have concentrated on effects to the seafloor environment. At Macaulay Point, sediment chemical levels of concern were confined to within 100 to 400 m of the outfall. Similarly, sediment toxicity was detected at stations up to 400 m from the diffusers. This toxicity was limited to effects on growth and development. Survival was not affected. The benthic infaunal community exhibited a typical response to organic enrichment. Within 100 m of the outfall abundance was increased and richness depressed. At Clover Point sediment chemical levels of concern were confined to within 100 to 200 m of the outfall. Tissue chemistry of resident mussels showed no consistent pattern with distance from the outfall. Some tissue chemicals increased with distance from the diffuser while others decreased. Overall the impact of the outfalls on the seafloor was found to be minimal and restricted in extent.

Ecological monitoring studies for volos sea outfall (Pagassitikos Gulf, western Aegean Sea)

Nutrient pollution in Pagassitikos Gulf arises mainly from the disposal of Volos untreated domestic wastewater inside Volos Bay, and also the agricultural run-off from the surrounding the Gulf cultivated areas. Volos Bay's limited circulation provides the conditions for the Bay's eutrophication by the discharge of untreated wastewater. In July 1987 this surface discharge was replaced by a new deep outfall system. The latter was located outside Volos Bay discharging primary treated effluents offshore at a depth of 55 m. To monitor any ecological changes, pre-operational (1986-1987) and operational (1988-1989) oceanographic data have been compared. The results showed a decrease in nutrient and phytoplankton concentrations between pre-operational and operational periods. Furthermore, in the vicinity of the present discharge a significant increase in the abundance of benthic communities occurred, due presumably to the continuous supply of food, adequate water circulation and high dissolved oxygen levels.

Ecological monitoring studies for volos sea outfall (Pagassitikos Gulf, Western Aegean Sea)

Nutrient pollution in Pagassitikos Gulf arises mainly from the disposal of Volos untreated domestic wastewater inside Volos Bay, and also the agricultural run-off from the surrounding the Gulf cultivated areas. Volos Bay's limited circulation provides the conditions for the Bay's eutrophication by the discharge of untreated wastewater. In July 1987 this surface discharge was replaced by a new deep outfall system. The latter was located outside Volos Bay discharging primary treated effluents offshore at a depth of 55 m. To monitor any ecological changes, pre-operational (1986–1987) and operational (1988–1989) oceanographic data have been compared. The results showed a decrease in nutrient and phytoplankton concentrations between pre-operational and operational periods. Furthermore, in the vicinity of the present discharge a significant increase in the abundance of benthic communities occurred, due presumably to the continuous supply of food, adequate water circulation and high dissolved oxygen levels.

The ecological state of the Elefsis Bay prior to the operation of the athens sea outfall

Nutrient pollution in Elefsis Bay arises mainly from the disposal of Athens untreated wastewater at the eastern entrance of the Bay. The absence of river discharge, lack of cultivated agricultural areas providing runoff and the Bay's limited circulation provide the conditions for the Bay's eutrophication by the discharge of untreated wastewater. In the spring of 1993 this discharge was replaced by a new deep outfall system. To monitor any future changes an assessment of the present ecological state of the Bay is required. Analysis of appropriate data showed that Elefsis Bay accumulates nutrients. In summer a strong thermal stratification causes anoxic conditions to occur in the lower layer. The ecosystem exhibits reduced species diversity and strong oscillations of plankton annual cycles. Flagellates (Cryptomonas sp.) dominate the phytoplankton, followed by dinoflagellates (Gyrodinium aureolum, Prorocentum dentatum) and only in the spring diatoms (Nitzschia) predominate. The zooplankton was dominated by copepods (Acartia clausi) and cladoceran (Podon polyphemoides). Macrobenthos consists of a small number of pollution-resistant species of Polychaeta (Capitela capitata), whilst in summer only one species of Molluscs (Corbula gibba) survives.

Physical Oceanographic Studies for the Design of the Athens Sea Outfall (Saronikos Gulf, Greece)

The discharge of about 600 000 m3/day of untreated wastewater into the northern part of Saronikos Gulf constitutes the major source of pollution for the latter. To take corrective measures, a new treatment plant and sea disposal by a deep outfall system is under construction. The basic design concept is to produce a submerged sewage field below the pycnocline, during the stratified period, at a location where the ambient current field is strong enough to advect it diluted to the open sea. Accordingly, the objectives aimed at obtaining accurate descriptions of the annual variation of the density stratification regime and the local current field. The results obtained showed that during summer the density stratification off Psyttalia Island is sufficiently strong to warrant the submergence of the sewage field; moreover, coupled with the virtual absence of upwelling and the presence of a well organized current field ensures the adequate offshore dispersal of the diluted effluent plume.