Water Cascading Research Articles

Targeting water utilities for the threshold problem without waste discharge

Increasing water scarcity and stringent environmental regulation have necessitated effective water conservation policies. Pinch analysis has been proved as one of the powerful tools to locate targets of waste water minimization. Two earlier water pinch targeting methods known as Water Cascade Analysis and Material Recovery Pinch Diagram have focused on the “threshold problems”. However, these methodologies have not systematically analyzed the introduction of external utility. In this work, three scenarios are proposed for this reason. The “Infeasible Threshold Problem” is addressed prior to employing external utility through the proposed scenarios. By systematically analyzing this specific problem, it is revealed that existing Water Cascade Analysis method cannot locate correct infeasible targets. Some adjustments are proposed to deal with this drawback. Moreover, to illustrate the applicability of proposed scenarios, Water Cascade Analysis and Material Recovery Pinch Diagram approaches are utilized for addressing a literature problem as a case study. It is shown that harvesting the impure fresh water source with a higher quality, in the “threshold problem with zero discharge”, leads to more pure fresh water saving.

Major consequences of an intense dense shelf water cascading event on deep-sea benthic trophic conditions and meiofaunal biodiversity

Abstract. Numerous submarine canyons around the world are preferential conduits for episodic dense shelf water cascading (DSWC), which quickly modifies physical and chemical ambient conditions while transporting large amounts of material towards the base of slope and basin. Observations conducted during the last 20 yr in the Lacaze-Duthiers and Cap de Creus canyons (Gulf of Lion, NW Mediterranean Sea) report several intense DSWC events. The effects of DSWC on deep-sea ecosystems are almost unknown. To investigate the effects of these episodic events, we analysed changes in the meiofaunal biodiversity inside and outside the canyon. Sediment samples were collected at depths varying from ca. 1000 to > 2100 m in May 2004 (before a major event), April 2005 (during a major cascading event) and in October 2005, August 2006, April 2008 and April 2009 (after a major event). We report here that the late winter–early spring 2005 cascading led to a reduction of the organic matter contents in canyon floor sediments down to 1800 m depth, whereas surface sediments at about 2200 m depth showed an increase. Our findings suggest that the nutritional material removed from the shallower continental shelf, canyon floor and flanks, and also the adjacent open slope was rapidly transported to the deep margin. During the cascading event the meiofaunal abundance and biodiversity in the studied deep-sea sediments were significantly lower than after the event. Benthic assemblages during the cascading were significantly different from those in all other sampling periods in both the canyon and deep margin. After only six months from the cessation of the cascading, benthic assemblages in the impacted sediments were again similar to those observed in other sampling periods, thus illustrating a quick recovery. Since the present climate change is expected to increase the intensity and frequency of these episodic events, we anticipate that they will increasingly affect benthic bathyal ecosystems, which may eventually challenge their resilience.

Interaction of dense shelf water cascading and open‐sea convection in the northwestern Mediterranean during winter 2012

AbstractThe winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the Gulf of Lions. Multiplatforms observations enabled a synoptic view of dense water formation and spreading at basin scale. Five months after its formation, the dense water of coastal origin created a distinct bottom layer up to a few hundreds of meters thick over the central part of the NW Mediterranean basin, which was overlaid by a layer of newly formed deep water produced by open‐sea convection. These new observations highlight the role of intense episodes of both dense shelf water cascading and open‐sea convection to the progressive modification of the NW Mediterranean deep waters.

The piercing of the Atlantic Layer by an Arctic shelf water cascade in an idealised study inspired by the Storfjorden overflow in Svalbard

A plume of dense brine-enriched water, resulting from sea ice production in the Storfjorden polynya (Svalbard), cascades into Fram Strait and encounters a layer of warm, saline Atlantic Water. In some years the plume continues to sink into the deep Fram Strait while in other years it remains at Atlantic Layer depths. It has been unclear what parameters control whether the plume pierces the Atlantic Layer or not.We use a high-resolution 3-D numerical ocean model (NEMO-SHELF) to simulate an idealised scenario where a cascade descends a conical slope into an ambient 3-layer stratification. The model uses 1km horizontal resolution and a blend of s- and z coordinates with 42 layers in the vertical arranged to resolve the plume at the bottom. We vary the salinity ‘S’ and the flow rate ‘Q’ of the simulated Storfjorden overflow to investigate both strong and weak cascading conditions. In agreement with observations the model reproduces three regimes: (i) the plume is arrested within or just below the Atlantic Layer, (ii) the plume pierces the Atlantic Layer and continues to the bottom of the slope and an intermediate regime (iii) where a portion of the plume detaches from the bottom, intrudes into the Atlantic Layer while the remainder continues its downslope propagation. For our idealised case the cascading regime can be predicted from the initial values of S and Q. In those model experiments where the initial density of the overflow water is considerably greater than of the deepest ambient water mass we find that a cascade with high initial S does not necessarily reach the bottom if Q is low. Conversely, cascades with an initial density just slightly higher than the deepest ambient layer may flow to the bottom if the flow rate Q is high. A functional relationship between S/Q and the final depth level of plume waters is explained by the flux of potential energy (arising from the introduction of dense water at shallow depth) which, in our idealised setting, represents the only energy source for downslope descent and mixing.

Baffle-Drop Structure Design Relationships

A baffle-drop structure is a flow conveyance structure that can be used for transport of urban storm water down to underground storage tunnels. The water cascades down the structure from baffle to baffle and plunges into a pool at the bottom from where it is conveyed to the tunnel through an adit. The structure has been used successfully in a limited number of urban drainage schemes. However, its hydraulics and air entrainment characteristics are not fully understood. Using a series of laboratory experiments, an analysis has been tested and validated that may be used for design. The analysis provides a dimensionless relationship between key variables, including design discharge, shaft diameter, baffle spacing, and position of a vertical wall dividing the shaft in a dry and a wet portion. Using this relationship the shaft can be designed to maintain atmospheric pressure throughout its height with little or no air being entrained into the tunnel.

Pre‐modern Arctic Ocean circulation from surface sediment neodymium isotopes

AbstractWe present a survey of Nd isotopes measured from authigenic phases on surface sediments from the Arctic Ocean seafloor. Comparison with published dissolved water column Nd isotope distributions suggests that εNd from sediment leachates accurately represents bottom water circulation of the Arctic Ocean, with Atlantic (~−11 εNd) and Pacific (~−5 εNd) water end‐members clearly distinguishable. Nd isotopic data from the Chukchi margin show several apparent deviations from the expected pattern, which imply that this margin has been a region of sustained shelf‐to‐basin sediment redistribution and/or a region where deep water cascades downslope, such as through brine rejection during ice formation. These data also provide insights into a pre‐anthropocene “baseline” (several thousand years) for investigating Arctic Ocean circulation in a changing climate; the data presented here are indicative that these changes may be impacting the deep as well as surface ocean.

Calculation of the Cherenkov light yield from electromagnetic cascades in ice with Geant4

In this work we investigate and parameterize the amount and angular distribution of Cherenkov photons which are generated by electro-magnetic cascades in water or ice. We simulate electromagnetic cascades with Geant4 for primary electrons, positrons and photons with energies ranging from 1GeV to 10TeV. We parameterize the total Cherenkov-light yield as a function of energy, the longitudinal evolution of the Cherenkov emission along the cascade-axis and the angular distribution of photons. Furthermore, we investigate the fluctuations of the total light yield, the fluctuations in azimuth and changes of the emission with increasing age of the cascade.

Composite Table Algorithm - A Powerful Hybrid Pinch Targeting Method for Various Problems in Water Integration

Water management has become a very vital issue due to stringent environmental regulations and rising cost of water resources. Pinch analysis provides a conceptual approach for water network synthesis. Targeting is the first stage in most pinch analysis techniques to provide the baseline for detailed water network design. Although Water Cascade Analysis and Material Recovery Pinch Diagram methods have been developed to handle diverse water network problems, Composite Table Algorithm (CTA) is another water pinch targeting tool with its unique combination of both numerical and graphical characteristics. CTA was originally developed for fixed flow rate problems. In this work, the applicability of CTA for various water network problems such as fixed load, mixed fixed load and fixed flow rate, multiple pinch, and threshold problem is discussed. To facilitate, the approach has been programed in MATLAB and results obtained are validated by comparing with literature.

Southern Weddell Sea shelf edge geomorphology: Implications for gully formation by the overflow of high‐salinity water

Submarine gullies are the most common morphological features observed on Antarctic continental slopes. The processes forming these gullies, however, remain poorly constrained. In some areas, gully heads incise the continental shelf edge, and one hypothesis proposed is erosion by overflow of cold, dense water masses formed on the continental shelf. We examined new multibeam echo sounder bathymetric data from the Weddell Sea continental slope, the region that has the highest rate of cold, dense water overflow in Antarctica. Ice Shelf Water (ISW) cascades downslope with an average transport rate of 1.6 Sverdrups (Sv) in the southern Weddell Sea. Our new data show that within this region, ISW overflow does not deeply incise the shelf edge. The absence of gullies extending deeply into the glacial sediments at the shelf edge implies that cold, high salinity water overflow is unlikely to have caused the extensive shelf edge erosion observed on other parts of the Antarctic continental margin. Instead, the gullies observed in the southern Weddell Sea are relatively small and their characteristics indicative of small‐scale slides, probably resulting from the rapid accumulation and subsequent failure of proglacial sediment during glacial maxima.

Morphology and sediment dynamics of the northern Catalan continental shelf, northwestern Mediterranean Sea

The northern Catalan continental shelf, in the northwestern Mediterranean Sea, extends along 200km from the Cap de Creus submarine canyon to the Llobregat Delta, in the vicinity of the city of Barcelona. In this paper we present the results of a systematic investigation of this area by means of very high-resolution multibeam bathymetry to fully assess its morphological variability. The causative factors and processes determining such variability are subsequently interpreted.The shelf is divided in three segments by two prominent submarine canyons: the northernmost Roses Shelf is separated from the intermediate La Planassa Shelf by the La Fonera Canyon, while the boundary between the La Planassa Shelf and the southernmost Barcelona Shelf is marked by the Blanes Canyon. These two canyons are deeply incised in the continental margin, with their heads located at only 0.8 and 5km from the shore, respectively.The seafloor character reflects the influence of external controlling factors on the geomorphology and sediment dynamics of the northern continental shelf of Catalonia. These factors are the geological setting, the volume and nature of sediment input, and the type and characteristics of processes leading to sediment redistribution, such as dense shelf water cascading (DSWC) and eastern storms. The interaction of all these factors determines sediment dynamics and allows subdividing the northern Catalan continental shelf into three segments: the erosional–depositional Roses Shelf to the north, the non-depositional La Planassa Shelf in the middle, and the depositional Barcelona Shelf to the south. Erosional features off the Cap de Creus Peninsula and an along-shelf subdued channel in the outer shelf illustrate prevailing sediment dynamics in the Roses segment, which is dominated by erosional processes, local sediment accumulations and the southward bypass of sediment. The rocky character of the seafloor immediately north of the Blanes Canyon head demonstrates that neither significant sediment inputs from the Tordera River nor from the northern sources reach the southern part of the La Planassa Shelf. Palaeo-shorelines depict a number of paleodeltas with steep delta fronts on the drowned Barcelona Shelf.

Thick bottom nepheloid layers in the western Mediterranean generated by deep dense shelf water cascading

The analysis of a compilation of deep CTD casts conducted in the western Mediterranean from 1998 to 2011 has documented the role that dense water formation, and particularly deep dense shelf water cascading off the Gulf of Lions, plays in transporting suspended particulate matter from the coastal regions down to the basin. Deep CTD casts reveal that after the 1999 and 2005–2006 deep cascading events the Western Mediterranean Deep Water (WMDW) was characterized by the presence of a thick bottom nepheloid layer (BNL) that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading. This BNL can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of <0.1mg/l above background levels, reaching higher concentrations close to the continental rise, with near-bottom peaks >1mg/l. After winter 1999 the BNL spread from the Gulf of Lions and the Catalan margin over the northwestern Mediterranean basin, reaching west of the Balearic Islands and the Ligurian Sea, while after winters 2005–2006 the BNL covered the entire western Mediterranean basin. Thickness and concentration of the BNL tend to diminish with time but this trend is highly dependent on the volume of dense water generated, both by convection and cascading. After winter 1999 the BNL signal vanished in one year, but after winters 2005–2006 it lasted for longer and the turbidity signal can still be distinguished at present (2011). Particle size distribution in the BNL reveals the presence of large aggregates up to 1mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern Mediterranean slope and basin. Results presented in this paper highlight the fact that the WMDW can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events, being a key process that could ultimately affect deep-sea biogeochemical cycles in the western Mediterranean.

Role of Dense Shelf Water Cascading in the Transfer of Organochlorine Compounds to Open Marine Waters

Settling particles were collected by an array of sediment trap moorings deployed along the Cap de Creus (CCC) and Lacaze-Duthiers (LDC) submarine canyons and on the adjacent southern open slope (SOS) between October 2005 and October 2006. This array collected particles during common settling processes and particles transferred to deep waters by dense shelf water cascading (DSWC). Polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlorobenzenes (CBzs)--pentachlorobenzene and hexachlorobenzene--and hexachlorocyclohexanes were analyzed in all samples. The results show much higher settling fluxes of these compounds during DSWC than during common sedimentation processes. The area of highest deposition was located between 1000 and 1500 m depth and extended along the canyons and outside them showing their channelling effects but also overflows of dense shelf water from these canyons. Higher fluxes were observed near the bottom (30 m above bottom; mab) than at intermediate waters (500 mab) which is consistent with the formation and sinking of dense water close to the continental shelf and main displacement through the slope by the bottom. DSWC involved the highest settling fluxes of these compounds ever described in marine continental slopes and pelagic areas, e.g., peak values of PCBs (960 ng · m(-2) · d(-1)), DDTs (2900 ng · m(-2) · d(-1)), CBzs (340 ng · m(-2) · d(-1)) and lindane (180 ng · m(-2) · d(-1)).

Efficient Ce(III)-Catalyzed cis-Selective Synthetic Approach to γ-Lactones in Aqueous Media

The first CeCl3 · 7H2O-catalyzed, one-pot synthesis of α-mercapto-γ-lactones via regioselective epoxide ring opening and mercaptoacetylative cyclization cascades in water is reported. The reaction between 2-methyl-2-phenyl-1,3-oxathiolan-5-one and a variety of terminal epoxides was carried out in aqueous media to afford γ-lactones in good to excellent yields (83–94%) with complete cis diastereoselectivity. Acetophenone obtained as a by-product was also recovered and recycled easily for further use.

The Design for Feed Water System of Boiler Based on Fuzzy Immune Smith Control

Aiming at the uncertainty of model parameters and dominate time delay of the controlled object in feed water system of boiler, combined with improved Smith predictor control method and fuzzy immune PID control method, improved Smith predicting controller based on fuzzy immune is designed. Fuzzy Immune PID controller can self-tune parameters, and has adaptive capacity to the diversification of controlled object parameters. When there is the phenomenon of large delay, the predictor estimates in advance the dynamic characteristics of the process under basic disturbance, so that regulator takes action ahead of time to reduce the overshoot. The designed controller is applied to the feed water cascade control system, and is simulated by Matlab under different operating conditions. Simulation results show that the designed control system has strong adaptive ability to the diversification of model parameters. And its stability, accuracy are superior to that of conventional Smith control system. The effectiveness of this designed controller has been confirmed.

Recycling of bleach plant effluent of an Indian paper mill using water cascade analysis technique

A systematic approach to optimizing water network has traditionally been utilized to examine and plan water conservation in industrial processes. In the present case study, water cascade analysis was used to analyze and optimize the water network of a bleaching section of an Indian paper mill. Water system integration can minimize both the freshwater consumption and wastewater discharge of a paper mill. Three limiting constraints, i.e., Chemical oxygen demand, Total dissolved solids, and Adsorbable organic halides (AOX), were considered for the study; after analysis, AOX was found to be a critical limiting constraint. A nearest neighbor algorithm (NNA) was used to distribute the fresh water and recycled water among the plant operations. After the application of WCA and NNA in the bleaching section, 41.75% of fresh water consumption and 70.67% of wastewater generation could be reduced.

Thermohaline variability and Antarctic bottom water formation at the Ross Sea shelf break

We use hydrological and current meter data collected in the Ross Sea, Antarctica between 1995 and 2006 to describe the spatial and temporal variability of water masses involved in the production of Antarctic Bottom Water (AABW). Data were collected in two regions of known outflows of dense shelf water in this region; the Drygalski Trough (DT) and the Glomar-Challenger Trough (GCT). Dense shelf water just inshore of the shelf break is dominated by High Salinity Shelf Water (HSSW) in the DT and Ice Shelf Water (ISW) in the GCT. The HSSW in the northern DT freshened by ∼0.06 in 11 y, while the ISW in the northern GCT freshened by ∼0.04 in 8 y and warmed by ∼0.04 °C in 11 y, dominated by a rapid warming during austral summer 2001/02. The Antarctic Slope Front separating the warm Circumpolar Deep Water (CDW) from the shelf waters is more stable near GCT than near DT, with CDW and mixing products being found on the outer DT shelf but not on the outer GCT shelf. The different source waters and mixing processes at the two sites lead to production of AABW with different thermohaline characteristics in the central and western Ross Sea. Multi-year time series of hydrography and currents at long-term moorings within 100 km of the shelf break in both troughs confirm the interannual signals in the dense shelf water and reveal the seasonal cycle of water mass properties. Near the DT the HSSW salinities experienced maxima in March/April and minima in September/October. The ISW in the GCT is warmest in March/April and coolest between August and October. Mooring data also demonstrate significant high-frequency variability associated with tides and other processes. Wavelet analysis of near-bottom moored sensors sampling the dense water cascade over the continental slope west of the GCT shows intermittent energetic pulses of cold, dense water with periods from ∼32 h to ∼5 days.

Hydrography of the eastern part of the Aegean Sea during the Eastern Mediterranean Transient (EMT)

Hydrographic features of the Aegean Sea were studied using CTDs collected in 4 cruises from 1991 to 1993. This period covers an interesting large-scale change in the thermohaline circulation in the Eastern Mediterranean and the Aegean Sea known as the Eastern Mediterranean Transient (EMT) and was first described during early 1990s. The cruise data is analyzed to depict the spatial variability of the water masses of the Aegean Sea in this period. We found Levantine Waters to be particularly prominent during the spring of 1992, more than in the other seasons. In the Central Aegean Sea the circulated cold water mixes with the upwelling water and very dense water remains behind in summer 1991. The Levantine Surface Water (LSW) is blocked and does not penetrate further to the north because of the existing upwelling water seen near Saros (Buyukkemikli Cape) and off-shore side of Baba Cape (product of northerly wind) especially in summer 1991 and in fall 1992. The water masses are nearly homogeneous vertically with the influence of strong wind and convective mixing in winter time. In this study, we underline the contribution of the eastern part of the Aegean to the rising isopycnal levels during the EMT. In turn, i) the dense water cascades from eastern shelf of the Aegean Sea, ii) the upwelling and downwelling processes in the northern and central basins, iii) the cooling effect of Black Sea Water (BSW) on upwelled water at the south of the Lemnos Island (open sea convection) and iv) local wind forcing.

Achieving Dewaterization in Industrial Parks

Summary Water resource management is a critical component of eco-industrial parks. This article proposes a methodology, termed the water resource management model for industrial parks, that integrates a water input-output table with water pinch technology. A case study of the Yixing Economic Development Zone (YEDZ) in China illustrates the methodology. Each sector's water utilization and direct and indirect intersectoral interactions of water and water pollutants in 2007 and 2015 are accounted for. It is proposed that water metabolism in 2015 could achieve certain objectives of water resource management in the YEDZ. In addition, future policies are proposed. The YEDZ needs to focus on improving various technologies regarding the manufacture of textiles, the manufacture of raw chemical materials and chemical products, and the production and supply of electric and heat power—which will promote the utilization of water cascading among sectors and encourage the reuse of treated water from wastewater treatment plants. Last, future work for water resource management is proposed.

Dense shelf water formation along the south-west Australian inner shelf

[1] Hydrological data from a repeated cross-shore transect obtained using Teledyne Webb Research Slocum Electric gliders offshore Two Rocks in south-western Australia over 13 months are presented. The data revealed that formation of dense water inshore and its transport across the shelf as a near bed gravity current (defined as Dense Shelf Water Cascade, DSWC) was a regular occurrence, particularly during autumn and winter months. In autumn, the dense water is mainly formed through changes in salinity resulting from evaporation, whilst in winter; temperature change through surface cooling was the dominant factor. The mean wind speeds also decrease during the transition during autumn. The speed of the DSWC was estimated to be 0.01–0.02 m s−1, and similar to that measured in other selected regions globally. The offshore transport from the shelf is a significant component of the alongshore wind-driven transport.

Cover Picture: Oral, Direct Thrombin and Factor Xa Inhibitors: The Replacement for Warfarin, Leeches, and Pig Intestines? (Angew. Chem. Int. Ed. 20/2011)

The large water cascade (ital. cascare=to fall) in the baroque landscaped park Wilhelmshöhe in Kassel (Germany) is reminiscent of the blood-clotting cascade in which the different clotting factors initiate the formation of fibrin thrombi in an amplification cascade. This protective mechanism against blood loss is, however, also the cause of thrombotic diseases. In order to inhibit it an extensive search for low-molecular-weight factor Xa and thrombin inhibitors has been carried out. More on this in the Review by A. Straub et al. on page 4574 ff.