Outfall Channel Research Articles

Dimensioning of Required Volumes of Interconnected Detention Tanks Taking into Account the Direction and Speed of Rain Movement

This article is aimed at defining the impact of the direction and velocity of waves of rainfall as they pass over interconnected stormwater detention tank systems. The simulations were conducted for a real urban catchment area as part of the Storm Water Management Model (SWMM) 5.1 programme. The results permit us to conclude that the direction and velocity of a moving wave of rainfall have a significant influence on the required volumes of interconnected stormwater detention tank systems. By comparing the modelling test results for stationary rainfall and rainfall moving over the urban catchment area, it has been demonstrated that differences in the required volume of the detention tank located at the terminal section of a stormwater drainage system are inversely proportional to the adopted value of the diameter of the outfall channel for upstream storage reservoirs. In extreme cases, the differences may be up to several dozen percentage points. Furthermore, it has been proven that the arrangement of the stormwater detention tanks in relation to one another and the adopted diameter of the outfall channel are key factors in identifying the degree to which the detention tanks are hydraulically dependent on one another.

Multiple analysis approach for the design of the labyrinth spillway on the Nam Teng river, Myanmar: Concept design - CFD - physical model

This paper presents the results of a combined approach - concept design, Computational Fluid Dynamics (CFD) simulations and physical model test - to design a spillway on the Nam Teng River in Myanmar. The spillway includes a 140 m wide labyrinth weir which ensures that the PMF flow QPMF=6800 m3/s passes with a maximum head of 5.5 m. The width required to pass PMF flow for a conventional ogee shaped weir is ca. 200m. The design of the spillway is based on design recommendations for labyrinth weirs from Tullis [1] and USBR guidelines to design the chute, stilling basin and outfall channel that leads the flood flow back to the river. The CFD simulations helped to improve the flow condition at the entrance and towards the labyrinth weir by altering the approach channel. The physical model tests confirmed the capacity of the labyrinth weir, investigated blockage risk due to floating debris. The design modifications made based on the physical model tests have increased the hydraulic performance and safety of the spillway and made the construction cheaper and simpler (less excavation and civil work).

Evaluation of Sediment Diversion Design Attributes and Their Impact on the Capture Efficiency

AbstractMany riverine systems have been disconnected from their receiving basins by flood-protection levees and other engineered systems. Reconnecting these alluvial rivers with their receiving basins is a viable option to nourish and sustain existing coastal wetland systems as well as to build new land. This sediment nourishment can be accomplished through direct dredging and placement or through sediment diversions. Efficient design of sediment diversions is important to maximize the land building potential. This study’s objective is to quantitatively identify key design attributes of sediment diversions, influencing their ability to capture sediment. The outfall channel alignment angle (ϕ), intake invert elevation, and diversion size are hypothesized as key parameters. The analysis is limited to sediment grain sizes larger than 63 μm and has been performed using a validated three-dimensional numerical model. A time integrated sediment-water ratio was used as an indicator to reflect efficiency of sedime...

Numerical Modelling of the Coastal Thermal Water Transport for CALACA Power Plant, the Philippines

Based on numerical simulations, the hydrodynamics and thermal water transport characteristics of the Calaca Power Plant, the Philippines were studied. Through analysis, after the extension of power plant capacity, the temperature difference between the intakes and 100m offshore to the outfall channel entrance is 2.2°C, which meets the local standard of the Philippines government regulation. Therefore, the extension of the power plant capacity would not affect the electricity generation efficiency.

Physicochemical and Microbial Composition of Wastewater Samples Collected from a Petrochemical Company in Southern Nigeria

The present study investigated the physicochemical and microbial composition of wastewater samples collected from a petrochemical company in Ekpan, Delta State, Nigeria. The aim was to investigate whether these effluent discharges met international standards for safe limits. Waste water samples were collected within the month of April, 2012, from three points, including petrochemical channel (PC), outfall channel (OC) and saver pit (SP). The control was raw water (tap water) for general use in the company. Results showed that following statutory provisions of Nigerian Federal Environmental Protection Agency in 1991 and the Canadian Council of Ministers of the Environment in 1995, waste water samples collected did not pose any environmental risk even when let into open waters. Fungi species identified in the water samples were Aspergillus niger, Fusarium solani, Penicillium sp., and Trichoderma sp. Bacteria species included; Micrococus varians, Bacillus subtilis, Pseudomonas putida, Proteus vulgaris and Bacilus pumilis.

Unraveling the decolourizing ability of yeast isolates from dye-polluted and virgin environments: an ecological and taxonomical overview

Microcosm assays with dye-amended culture media under a shot-feeding strategy allowed us to obtain 100 yeast isolates from the wastewater outfall channel of a dyeing textile factory in Tucumán (Argentina). Meanwhile, 63 yeast isolates were obtained from Phoebe porphyria (Laurel del monte) samples collected from Las Yungas rainforest (Tucumán), via a classical isolation scheme. Isolated yeasts, both from dye-polluted and virgin environments, were compared for their textile dye decolourization ability when cultured on solid and liquid media. Nine isolates from wastewater and 17 from Las Yungas showed the highest decolourization potential on agar plates containing six different reactive dyes, either alone or as a mixture. Five yeasts from each environment were further selected on the basis of their high dye removal rate in Vilmafix(®) Red 7B-HE- or Vilmafix(®) Blue RR-BB-amended liquid cultures. Yeasts from wastewater showed slightly higher decolourization percentages after 36 h of culture than yeasts from Las Yungas (98-100% vs. 91-95%, respectively). However, isolates from Las Yungas exhibited higher specific decolourization rates than isolates from effluents (1.8-3.0 vs. 0.9-1.3 mg g(-1)h(-1), respectively). All selected isolates were first grouped according to microsatellite-PCR analysis and representative isolates from each group were subsequently identified based on the 26S rRNA gene sequence analysis. Yeasts from wastewater were identified as the ascomycetous Pichia kudriavzevii (100%) and closely related to Candida sorbophila (99.8%), whilst yeasts from Las Yungas were identified as the basidiomycetous Trichosporon akiyoshidainum and Trichosporon multisporum. It is suggested that findings concerning yeast selection during screening programs for dye-decolourizing yeasts may be explained in the light of the copiotroph-oligotroph microorganisms rationale.

Analyses of three native aquatic plant species to assess spatial gradients of lake trace element contamination

A bioaccumulation study was performed on Lake Averno, a volcanic lake close to Naples (southern Italy), to ascertain the degree of trace element contamination. Good information to assess spatial gradients of Cd, Cr, Cu, Fe, Ni, Pb, V and Zn contamination was provided by analysing Phragmites communis roots, Najas marina shoots, Potamogeton pectinatus leaves and surface sediments of Lake Averno collected from July 1999 to July 2000 at three sites in the littoral zone. The highest concentrations of the trace elements were measured in sediments and plants from the site where a nearby sewage outfall channel reaches the lake, the lowest at the site below woodland. Significant correlations were found between sediment and plant element concentrations. For almost all the elements, values 2–4-fold higher were found for the site affected by the sewage effluent. Among the plant species, Ph. communis is the most useful species in biomonitoring studies due to its ability to accumulate trace elements in the roots and its collectability throughout the year. Given the absence of systematic water quality monitoring, trace elements in plants, rather than sediments, provide a cost-effective means for assessing trace element accumulation in aquatic systems during plant organ lifespan.

Factors Limiting Colonization of Western New York Creeks by the Zebra Mussel (Dreissena polymorpha)

The New York State Erie Barge Canal was first colonized by the zebra mussel (Dreissena polymorpha) in 1989. Canal water supplements flows in many creeks in western New York, including six creeks in Monroe County that have not been colonized by zebra mussels. We chose Salmon Creek to study why zebra mussels have not colonized regional creeks because the rocky substrate of the creek appears ideal for colonization, yet 100 meters downstream from the input of canal water to the creek adult zebra mussel densities drop to less than one mussel m−2. In the summer of 1993 veliger counts in the canal averaged 52 times greater than they were in Salmon Creek, yet water quality, current velocity, and particulate organic carbon concentrations in the creek and the canal were very similar. Chlorophyll a in the canal was higher than in the creek. Given the appropriate physical habitat and water quality conditions and an abundant source of veligers, the factors limiting zebra mussel colonization in Salmon Creek remain unknown, but three factors appear important: 1) Partial retention of zebra mussel veligers by the wetland through which the canal discharge flows, 2) Filtering of phytoplankton and veligers by the dense bed of adult zebra mussels at the beginning of the outfall channel from the canal to the creek, or 3) Inappropriate food quality (e.g., lack of phytoplankton with important fatty acid constituents) in the creek.

Hydraulic model investigation of downstream erosion of large regulators: a case study

Flow conditions, which could not be explained, occurred in the stilling basin and outfall channel of the Feni Regulator sited at the western end of the Feni River closure dam. This regulator controls outflows from the upstream reservoir which supplies irrigation water to Muhuri Project in Bangladesh. Analysis of flood discharge data revealed that the design discharge for the structure was not exceeded; yet abnormal scour occurred in the outfall channel and the brick block rip-rap placed thereon was damaged. A model study was conducted to understand the causes of such unusual local erosion downstream of the stilling basin and to provide answers to two main questions: Using a 1:30 scale model, the probable maximum scour was simulated, and the performance of alternative rip-rap designs including that of the existing one were examined. The results of this study supplemented by field scour data collected during subsequent flood seasons indicated that even if the flow rate through the regulator approaches the design flood discharge, the downstream scour is not likely to extend up to an elevation of − 10.7 m, a scour level observed in the previous year at a lower discharge. It also showed that the existing rip-rap blocks were marginally undersized and consequently the rip-rap was prone to failure if flow conditions departed from uniform. A suitable method of scour protection downstream of the stilling basin at the regulator exit also evolved from the study.

Acute bioassays with benthic macroinvertebrates conducted in situ.

Several methods of toxicity testing using macroinvertebrates in controlled laboratory experiments have been reported. Researchers conducted bioassays with natural assemblages of benthic macroinvertebrates exposed to several petroleum refinery effluents. They found that the populations of invertebrates declined after only a few days of exposure. The objective of the study was to determine the acute toxic effects of discharge water from a petrochemical complex on a natural assemblage of benthic macroinvertebrates. The discharge water consisted of refinery wastewater and sanitary wastewater, as well as brine discharge from a power/desalination plant. The benthic macroinvertebrates were transplanted from a healthy reef area to the outfall channel receiving the discharge water. The study began on October 7, 1985, and concluded that same week. Any decrease in specific species would indicate that the discharge was toxic to these species. These species could also serve as indicators of toxic conditions at other locations.

DISSIPATION OF WAVE ENERGY IN A SEAWATER OUTFALL CHANNEL

This paper describes the investigation of means of reducing wave action reaching the shoreward end of a power station cooling water outfall channel without resulting in significant head loss to the outflowing water. A variety of conceptual methods of reducing wave action in the outfall channel was examined. A physical model of the outfall was constructed. It was found that a rubble mound wave energy dissipator located in the outfall channel dramatically reduced wave action at the discharge seal pit.