Brackish Seawater Research Articles

Twenty-five years of desalination in the Canary Islands: an historical review of the application of reverse osmosis using case studies and operational experience

The need for a good quality water in the Canary Islands was, and continues to be, the driving force for the use of reverse osmosis to desalinate brackish water and seawater for irrigation and potable use. A number of case histories are presented which show the development of the use of reverse osmosis, from the small plants built 25 years ago in the early 1970s to current-day use. The case histories show not only the increase in use of reverse osmosis but also plot the development of the performance of the available membranes. The case studies show the importance of bringing previous experience to the design and direct technical support to the customer by the membrane supplier in order to ensure satisfactory long-term stable system performance.

Pilot Scale UF and RO Studies on Water Reuse in Corrugated Board Industry

The coloured effluents from pulp and paper mill industry are treated anaerobically and/or aerobically by a two stage membrane system with high efficiency. Three different types of membranes (UF and RO (BW and SW)) were used in the experiments. Surface area of each membrane was 2 m2. The combination of ultrafiltration (UF) and reverse osmosis (RO) treatment achieve a very high removals of COD (98-99%), colour and conductivity. At the end of a single pass with RO using seawater (SW) membrane, the initial COD, colour and conductivity values were reduced to 10–20 mg/l, 0–100 Pt-Co units and 200–300 μs/cm, respectively. The influent, UF permeate, RO permeates for brackish water (BW) and seawater (SW) membranes were 6000–6700 μs/cm, 5500–5900 μs/cm and 200–300 μs/cm, respectively. Excellent conductivity rejections were obtained in the UF and RO membrane systems. Almost complete colour removals were achieved in the RO experiments with SW membranes. RO studies with BW membranes were also performed with the same permeate from the first stage UF study. The observed flux has declined with time and membranes were cleaned periodically to maintain a constant flux. Applying this advanced membrane treatment technology, it is clear that about 60 percent of the process water can be recycled in the investigated industry.

Genetic structure of island populations of the anurans rana temporaria and bufo bufo

Amphibians have traditionally been considered to have low dispersal ability and they have become a model for studies on the effects of man-made habitat fragmentation on genetic variation and population differentiation. This study examined the genetic population structure in the common frog (Rana temporaria) and the common toad (Bufo bufo) in an archipelago of the northern Baltic Sea. Heterozygosity was not correlated with distance of the island from the mainland nor, in R. temporaria, with effective population size based on census estimates. Generally, no inbreeding was detected in island populations. The overall differentiation among islands was weak, but the FST values were significantly larger in R. temporaria (FST = 0.068) than in B. bufo (FST = 0.019). Most of the differentiation was a result of differences among groups of islands, differentiation within them playing a minor role. Thus, assuming Wright's island model of migration, gene flow was rather high among closely located islands, but longer distances seemed to form a slight dispersal barrier for R. temporaria. Strong gene flow within the study area was confirmed by lack of isolation by distance. The estimated effective population sizes in R. temporaria were small, the average being 32 breeding females per island. The results indicate that gene flow between island populations across the matrix of open, brackish-water sea is extensive and suggest that the anurans are well able to disperse in this natural metapopulation system.

Diatom stratigraphy in five offshore sediment cores from the northwestern Baltic proper implying large scale circulation changes during the last 8500 years

Five Holocene sediment cores from the northwestern Baltic proper were analysed for lithology, siliceous microfossil assemblages and geochemical parameters. The data indicate that surface water salinity and redox conditions below the halocline have changed drastically at least four times since the Baltic Sea changed from a fresh water lake (the Ancylus Lake) to a semi-enclosed brackish water sea (the Litorina Sea) c. 8500 yrs BP. These variations appear to be mainly effects of changes in water depth at the thresholds of inlet areas. Based on these changes, and earlier studies of the shoreline displacement in the inlet areas, we propose a tentative model for changes of large scale water circulation in the Baltic Sea during the last c. 8500 yrs. At the transition from fresh to brackish water 8500 14C yrs BP, upwelling of nutrient rich bottom water started to occur, causing a slight increase in primary production. Diatom assemblages in sediments indicate a slow rise in surface water salinity during this period. At 7000-6500 14C yrs BP, surface water salinity and primary production simultaneously increased, as anoxic bottom conditions were established at depth below the halocline. We suggest that high primary production was caused by increased input of oceanic water, leading to increased upwelling of nutrient rich bottom water. At the anoxic bottoms laminated sediments formed until 5000-4500 14C yrs BP. This period (c. 7000-4500 14C BP) was contemporaneous with the post-glacial transgression maximum in Oresund, and we suggest it represents the most saline phase of the Baltic Sea post-glacial history. Due to a regression in Oresund starting 4500 14C yrs BP, upwelling decreased and the halocline was lowered, resulting in decreased primary productivity and hence oxic deep water conditions. The diatom assemblages of the sediments indicate a lowering of salinity at the beginning of this period. We suggest that the second period of anoxic bottom conditions c. 2000-1500 14C yrs BP was caused by a change of dominating inflows from the Oresund to the Belt Sea. This resulted in decreased salinity of the inflowing water which did not penetrate to the deepest parts of the basin as frequently as before. The diatom record indicates both a second lowering of salinity and a change in the large scale water circulation at the beginning of this period.

Formation of Reaction Product Layers on Copper Alloys in Chloride Solutions

Copper and copper alloys are widely used in marine applications. This is mainly due to their inherent corrosion resistance and antifouling capability. The corrosion resistance of copper and its alloys depends on the formation of a protective reaction product layer. Various opinions on reaction product layer formation mechanisms have been presented. In this paper the formation of reaction product layers on copper and copper alloys was studied in the laboratory and under field conditions in brackish sea water. The laboratory studies included polarization curves, cyclic voltammetry and Contact Electric Resistance measurements. During immersion tests passivation was monitored by polarization resistance and corrosion potential measurements. The polarization curves showed, that addition of chlorides in the solution will decrease corrosion potential and cause a rapid dissolution reaction at the same potential that is the corrosion potential in chloride-free solution. Cyclic voltammetry results showed, that without chlorides the layer may contain several oxide and hydroxide phases. The pH and copper chloride complex concentration at the surface must be high enough for nucleation of cuprous oxide. The Contact Electric Resistance results showed, that the first anodic current peak in cyclic voltammograms is not necessarily caused by reaction layer product formation. The CER results show that the reaction product layer resistance begins to increase at 100-200 mV higher potentials in chloride solutions than in chloride-free solutions. The immersion tests showed again, that the formation of the reaction product layer may take a long time. Especially corrosion resistant copper-nickel alloys in lean brackish sea water had a stable corrosion potential only after several weeks.

Performance of a flash desalination unit intended to be coupled to a solar pond

Desalination remains an important possibility to produce water especially in regions where rainfall is scarce. Unfortunately desalination is an energy intensive operation whereas conventional fuel resources of many countries in the world are going to run out in a few years. The development of solar energy particularly for the purpose of sea brackish water desalination seems to be the best choice for these countries Our laboratory has contracted for a research program, with the financial support of the Secretary of State for Research and Technology, a prototype of desalination unit coupled to a 1500m 2 solar pond. In this paper we present some results obtained with a laboratory set up working under different conditions: temperature of brackish water and its flow rate, vacuum inside the evaporator chamber and spray methods, etc.... Compilation of these reuslts shows that 150 l/h of distilled water can be reached with only 1m 2 surface at 70°C. A numerical simulation of the whole system, based on experimental results obtained separately with the pond and the desalination unit, proves the competitivity of this technology.

Effects of dietary thyroid hormones on the red drum (Sciaenops ocellatus)

Four separate 8-week feeding trials were conducted to assess the effects of supplementing semipurified diets with either triiodothyronine (T3) or thyroxine (T4) at 0, 2, 10, and 50 mg/kg on growth and body composition of juvenile red drum (Sciaenops ocellatus) held in artificial brackish water (6‰) and artificial seawater (32‰). At both levels of salinity, increasing doses of T3 resulted in fish with reduced weight gain, feed efficiency, condition factor (weight × 100/length(3)), and muscle ratio (muscle weight × 100/body weight), as well as a lighter body color. Significant (p < 0.05) effects of T3 on the proximate composition of whole body, liver, and muscle were variable, generally reflecting decreased lipid and protein storage in liver and muscle, respectively. The two highest doses of T3 given to seawater adapted fish increased survival. Dietary T4 supplementation had no distinctive effects on appearance, growth or proximate body composition. These results indicate that whereas T3 may function to regulate protein and lipid metabolism in red drum, dietary supplementation with T3 leads to a hyperthyroidism-induced catabolic state. The elevated endogenous thyroid hormone levels found in fish fed optimal diets may thus adequately supply tissue needs during juvenile growth.

Outdoor pond cultivation of the subtropical marine red algaGracilaria tenuistipitata in brackish water in Sweden. Growth, nutrient uptake, co-cultivation with rainbow trout and epiphyte control

Pond cultivation of the subtropical, euryhaline macroscopic red algaGracilaria tenuisipitata var.liui Zhanget Xia was carried out in brackish seawater (6–7‰) in the Gryt archipelago on the east coast of Sweden, using four outdoor tanks of 30–40 m3. Growth rate and nutrient uptake in batch culture were measured with the aim of estimating the water purification capacity ofG. tenuisipitata in outdoor conditions. Its ability to withstand epiphytic infections was also studied. An average growth rate of 4‰ biomass increase per day was recorded during two seasons with a maximum growth rate of 9‰ d−1. The initial biomass was usually 1 kgFW m−3 (FW, fresh weight). The nutrient uptake capacity was on average ca. 1 g Ni kgFW−1 d−1 and 0.08 g Pi kgFW−1 d−1 and the uptake rates for NH4+-N were higher than those for NO3−-N. Both the growth rate and the nutrient uptake rate were highest at the highest water temperature. Co-cultivation with rainbow trout (Oncorhynchus mykiss) was tested: with trout fodder as the only nutrient inputG. tenuistipitata could grow and maintain low levels of Ni and Pi with optimum efficiency at a trout: alga ratio of 1:1 (w:w). Epiphytic growth of filamentous green and brown algae was limited, probably as a result of the high pH values caused by inorganic carbon uptake byG. tenuistipitata. The growth ofEnteromorpha intestinalis, the only significant epiphyte, was completely inhibited and the majority of plants died by a few days treatment with 100 µg 1−1 Cu2+, a concentration that did not severely affectG. tenuistipitata. We conclude thatG. tenuistipitata can be cultivated in outdoor ponds in southern Sweden during 5–6 months of the year using aerated or unaerated batch cultures and that wastewater from trout cultivation may be used as a nutrient source, resulting in purification with respect to N and P.

Elemental pollution of the golden horn surface sediments

The total and acid leachable composition of Golden Horn surface sediments have been investigated for Pb, Zn, Cu, Cr, Ni, Co, Mn and Fe. Quantitatively, the majority of the Pb, Zn and Cu defined to be from anthropogenic origin and the sediments classified as contaminated with respect to these elements. The natural change in the depth of halocline, results in the remobilization of loosely held metals from sediments. Mediterranean water is more effective in remobilization of the loosely held metals than the brackish Black Sea water.

Sweden Seeking New Technology to Combat Oil Spills

ABSTRACT Due to the special circumstances of the Baltic Sea—brackish water, low temperatures, ice, and widespread archipelagos—special oil spill response and cleanup methods and equipment have proven to be necessary. The Swedish Government therefore commissioned the Swedish National Board of Technical Development to establish a research and development program involving the six authorities that are responsible for the country's environmental protection. The first step in this program was a common document, Policy Guidelines for Swedish Maritime Oil Spill Protection in the 1990s, with high-priority strategies according to which all subsequent development has been carried out. The program has produced methods and systems ranging from those for handling oil spills at sea and from leaking wrecks, to protection against and deflection of oil from sensitive areas, and cleanup operations in the beach zone.

A successful rearing experiment with amago salmon ( Oncorhynchus masou rhodurus) in floating cages in the Adriatic Sea

In a rearing experiment on production on fish for consumption, 10 000 amago salmon ( Oncorhynchus masou rhodurus) eggs were imported to Yugoslavia from Japan. Incubation of eyed eggs and early rearing of fry up to smoltification followed the standard methods adopted for rainbow trout and coho salmon culture in Yugoslavia. Smolts of 40–60 g, obtained after a 10-month rearing period, were transferred to floating cages in brackish-sea water on the Adriatic coast. After another 7 months the fish had reached an average weight of 458 g, and an attractive coloration of silver with red spots. Taste and chemical composition of the meat matched that of cultured rainbow trout. Marked differences in body weight between male and female salmon emphasize the desirability of development of an all-female stock for cage culture. Fish left in cages during the summer showed no mortality although water temperatures as high as 26°C were observed. Due to the successful rearing of fry and acclimatization of smolts to cage culture in brackish-sea water, amago salmon appear to be very promising for commercial aquaculture in countries outside Japan.

Food selection in juvenile three-spined sticklebacks studied in relation to size, abundance and biomass of prey

The food selection and diet of juvenile three-spined sticklebacks (Gasterosteus aculeatus L.) was studied in the littoral of a brackish-water sea area. The sampling stations were located in a eutrophicated area, where the plankton was characterized by rotifers, in a noneutrophicated zone, where copepods predominated, and in the intermediate zone, characterized by cladocerans. In all areas the fish preferred microcrustaceans to rotifers, but they did not feed strictly according to the size-selection hypothesis. Nor did they take the most abundant prey species. With some exceptions the species chiefly eaten by and also selected by fish, were those which had the largest biomass in the plankton.

Variations of 87Sr/86Sr in Water from Streams Discharging into the Bothnian Bay, Baltic Sea

The 87Sr/86Sr ratio in 53 water samples were analysed, 26 from streams in Sweden, 22 from streams in Finland and 5 from the Bothnian Bay itself. The brackish seawater of the bay had the isotope ratio 0.7095, while the stream-water samples varied from 0.7177 to 0.7366. The weighted average isotope ratio with respect to discharges was 0.7313, this high ratio reflecting the dominance of granitic Proterozoic rocks in the region. For streams with an average discharge between 1-40 m3/s the isotope ratio was within the interval 0.718-0.736, while those with discharges &amp;gt;150 m3/s defined an interval of 0.728-0.735. The variations in isotope ratios are discussed with respect to bedrock geology of drainage basins, possible effects of seawater inundations and Postglacial uplift combined with the complex history of the Baltic Sea.

Mortality, growth and swim bladder stress syndrome of sea bass ( Dicentrarchus labrax) larvae under varied environmental conditions

Responses to variations in light, temperature and salinity by sea bass larvae are described here. Massive mortality of larvae has been common in Mediterranean culture efforts. This mortality, associated with swim bladder malfunction, has been analysed regarding its association with individual stresses. Optimum temperatures for sea bass growth are clearly unsuited to larval rearing, while brackish sea water (25‰) just as clearly improves growth and survival. Light and nutritional regimes as well as water quality are other sources of environmental stress that may induce the swim bladder stress syndrome (SBSS) and reduce growth and survival. SBSS should not be confused with “gas bubble” disease and its most effective treatment depends on an understanding of larval environmental requirements. Larval growth was enhanced by both decreased salinity and increased temperature, but not by increased light. SBSS and mortality were avoided only when larvae were held at ambient temperature (12.5°C), natural light, and reduced salinity (25‰). Larvae dying with distended swim bladders also had other symptoms of environmental stress—spinal abnormalities, calculi in the urinary bladders, copious mucous and opaque (edemous) tissues. Elevations of temperature and light, as well as ambient sea water (36‰) are environmental stressors and induce SBSS.

CRONIFER 1713 LCN

Abstract CRONIFER 1713 LCN is a fully austenitic low-carbon chromium-nickel-molybdenum stainless steel. It contains a nitrogen addition (0.10-0.20%) which helps to stabilize the austenite. Its molybdenum content (4.0-5.0%) provides good resistance to pitting attack by media containing chloride ions. Thus it has good resistance to brackish water and seawater. Typical applications are bleaching plants and equipment for handling aqueous chloride solutions. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-425. Producer or source: Vereingte Deutsche Metallwerke AG.

Measured and numerically-simulated autumn cooling in the Bay of Bothnia

Vertical temperature profiles are analysed for the case of cooling of brackish sea water around the temperature of maximum density. Field measurements in the Bay of Bothnia cover a period of 52 days, during which the surface water was cooled from 6°C to 1.5°C. A mathematical model, which is based on the conservation equations for momentum, heat and salt in their one-dimensional forms, is presented. The equation of state is linear with respect to salinity and quadratic with respect to temperature. Turbulent exchange coefficients are calculated with a two-equation model of turbulence. The measured temperature profiles clearly demonstrate the importance of both temperature and salinity gradients in the mixed-layer dynamics. The mathematical model describes these and the general development of the temperature profile in a most satisfactory way. DOI: 10.1111/j.1600-0870.1983.tb00200.x

Genetic variation between geographic populations of the amphipods Gammarus zaddachi and G. salinus

Spatial and temporal patterns of gene-enzyme variation were estimated in the sibling species Gammarus zaddachi Sexton and G. salinus Spooner by starch gel electrophoresis. Twenty-one G. zaddachi and 18 G. salinus populations from coastal and estuarine areas in the Baltic Sea, North Sea and other localities of north-western Europe were surveyed. Both amphipods display similar electrophoresis patterns of the enzyme systems studied. Considerable interspecific and interpopulational differences were detected in allele frequencies at three highly polymorphic loci, phosphoglucose isomerase (PGI), glutamate oxalacetate transaminase (GOT) and arginine phosphokinase (APK). G. zaddachi exhibits a pronounced genetic heterogeneity in most areas of the sampled range. Populations from northern French and western English coasts differ significantly from the other samples in allele frequencies at the PGI or APK locus, respectively. Baltic populations are widely uniform in their genetic composition but can be distinguished from samples taken at North Sea sites in allele frequencies at the APK locus. The latter reveal a clinal variation, ranging from the Danish to the French coast. In contrast to G. zaddachi, a low degree of genetic differentiation was observed among the G. salinus populations examined. This indicates that migration and interregional mixing may be more important in maintaining the genetic structure than in G. zaddachi which, compared to G. salinus, prefers habitats of lower salinity levels. Evidently, less extensive dispersal capabilities owing to the confinement of G. zaddachi to brackish waters of dilute salt concentrations may account for a diminished gene flow and considerable genetic separation of local populations. This assumption is supported by the genetic homogeneity documented in Baltic G. zaddachi populations. In view of the low and constant salinities in wide areas of this brackish-water sea such barriers do not exist. Survey studies performed with selected populations over a 3-yr period demonstrated a general pattern of temporal constancy in the allozyme variation observed.

The Relation of Treatment and Ecological Effects in Brackish Water Regions

The Relation of Treatment and Ecological Effects in Brackish Water Regions

A redescription of the brackish-water sea anemoneNematostella vectensisStephenson, with an appraisal of congeneric species

Summary A rare brackish-water sea anemone, Nematostella vectensis Stephenson, 1935, is redescribed. Some differences between previous descriptions are reconciled, in particular the cnidom measurements and variations in pigmentation. Relations with other members of the genus are discussed. The nominal species N. pellucida Crowell, 1946, is regarded as conspecific with N. vectensis. The morphology of the adherent rugae (used in burrowing and climbing), the morphology of a larval stage, the origin of the nematosomes (characteristic of the genus) and some notably malformed specimens of N. vectensis are all described for the first time. Specimens up to twice the maximum size of those previously described are recorded.

The Baltic salmon stock Its natural and artificial regulation

The Atlantic salmon, Salmo salar L., is represented in the Baltic area by a commercially exploited population, practically “landlocked” in this brackish-water sea. It displays long-term catch fluct...