Environmental impact of brine disposal on Posidonia seagrasses

Energy consumption of reverse osmosis seawater desalination - possibilities for its optimisation in design and operation of SWRO plants

The Ghalilah SWRO plant: an overview of the solutions adopted to minimize energy consumption

Different designs in energy savings of SWRO Plant of Las Palmas III

Water, otherwise known as the pool of life, is the very essence of all living things and as such is vital for survival, whether for living beings, social, economic development or for environmental sustainability. However, its continuing existence is severely threatened for future as a result of climate change, carbon footprint, population growth, environmental damage, combined with natural disasters like droughts and floods. The prospect of an alternative solution such as desalination of sea or brackish water to counter the limit on conventional water resources such as groundwater, which cannot meet demand, is therefore very promising, particularly in arid and semi-arid regions where water scarcity and impaired quality prevails. Consequently, desalination technology has now become a burgeoning industry in North Africa or southern Mediterranean countries, such as in Libya. However, evidence suggests that as a result of by-products being discharged directly into the sea, particularly from coastal desalination plants, the physico-chemical parameters of the receiving water are changing and posing a threat to marine ecosystems. As a result of studies conducted on these parameters to analyse the brine emitted from the Zwuarah and the West Tripoli distillation plants (ZWDP & WTRIS) on the Libyan coastline, evidence shows there is a significant positive correlation at both sites between the biological data and physico-chemical parameters (rs=0.673; p=0.002) and (rs=0.637; p=0.003), which is a clear indication of the impact of brine disposal from both plants on the marine environment. For most of coastal desalination plants on the Libyan coastline, the most practical and least expensive brine disposal option is to discharge it into the sea. It is necessary therefore, to effectively manage desalination reject brine in order to ensure more efficient disposal and reuse. Therefore, it is suggested that experimental studies are aimed for dual benefit of on-site generation of sodium hypochlorite through brine electrolysis and to recover minerals and NaCl from the brine using evaporation ponds, while protecting the environment. Following the first experiment, the outcome of brine utilisation showed a significant production of NaOCl using graphite electrodes (MCCA 1.82 gr/m3). At interelectrode spacing 2 cm and 4 cm, the power consumption was higher, with a greater concentration of sodium hypochlorite generation varying between 10-25 kw/m3 (573-2140ppm) and 29-24 kwm-3 (572-2600ppm) than at interelectrode spacing 6cm 17-13 kwm-3 (350-1790ppm). Consequently, the selection of an optimum electrical consumption level is key in establishing the best scenario in terms of economy and efficiency. Subsequent to the second experiment of brine evaporation in the ponds, results showed that the evaporation rate in August was lower than in September (9.06 mmday-1, 14.63 mmday-1) respectively. The results of the SEM/EDS test showed that due to elevated surges of Na+ and Cl-, halite (NaCl) was the main mineral evident during crystallisation of the salt samples. Hence, the two experiments reveal that brine can be recycled productively, while protecting the environment.

Economic evaluation of a new ultrafiltration membrane for pretreatment of seawater reverse osmosis

Retro-fitting existing SWRO systems with a new energy recovery device

Organic carbon movement through two SWRO facilities from source water to pretreatment to product with relevance to membrane biofouling

Hollow fiber type PRO module and its characteristics

The San Pedro del Pinatar I and II desalination plants in Spain were constructed near Posidonia oceanica meadows protected at the national and European level. The environmental impact statement for these plants stipulate that the brine discharge from the plant must not impact the meadows. To this end, a 4790 m submerged outfall was constructed to bypass the lower limit of the seagrass meadows, and a diffuser piece, along with an outfall pumping system, was installed at the end of the outfall. The objective of this paper is to evaluate the economic cost of the energy consumed for the brine discharge evacuation process necessary to comply with environmental requirements. The operating time and power consumption data were obtained from the plant’s monitoring system, while the energy cost was obtained from energy invoices. The computed results show that it is possible to minimize the environmental impacts of brine discharge on the marine environment of an SWRO plant with a low economic cost. The average energy consumption of the reject effluent pumping system ranged from 19.4 to 1239.3 thousand kWh per year, while the average annual energy cost was 49,329 €, which amounts to only 0.56% of the total energy cost for plant operation. The adoption of these measures provide a cost-effective means to meet environmental protection requirements and minimize the environmental impact associated with the discharged brine. As the demand for desalination operations increase, economically and scientifically viable technologies for mitigating environmental impacts are necessary for sustainability in this domain.

Physical and chemical assessment of MSF distillate and SWRO product for drinking purpose

Ocean acidification may be one of the greatest challenges facing 'Society over the next SO- 100 years. In the Mediterranean Sea, meadows of the seagrass <i>Posidonia oceanica</i> play a pivotal role in coastal systems, providing shelter and food for a highly diversified plant and animal community, and nursery for several commercial species of fish and bivalves. This thesis aims to provide a broad overview of the effect of acidification on <i>P. oceanica</i>, and its associated community, through observation of seagrass meadows associated with subtidal CO₂ vents off the Castello Aragonese, Ischia, Italy. Control (mean pH 8.1) and acidified (mean pH 7.8) stations were situated in seagrass meadows on both the north and south side of the Castello Aragonese. Research was concentrated into three main objectives; to investigate the effect of acidification on 1) plant structure and function, 2) invertebrate community dynamics, and 3) macroherbivore grazing pressure. Results suggested that <i>P. oceanica</i> and its associated community should be robust to levels of acidification projected for the end of this century. Seagrass density, invertebrate abundance, and <i>P. oceanica</i> grazing pressure all increased in response to acidification. Although a slight decrease in invertebrate diversity was observed in 'acidified stations, species richness was maintained. Increased grazing by the fish <i>Salpa salpa</i> was most highly correlated to a decrease in epiphytic algal cover and C:N content of the [eaves, and an increase seagrass density. Whilst fish may select leaves with low algal cover and C:N content, previous research suggests that increased shoot density is a response to high grazing pressure. The abundance of many groups of invertebrate taxa was positively correlated to shoot density, whilst decapods decreased during months of reduced canopy height, suggesting changes in <i>P. oceanica</i> condition variables, in response to acidification, may lead to a cascade of indirect effects which have positive or negative influences on the abundance of the associated invertebrate community. One of the most striking findings of this thesis was the ability of calcifying species to persevere, and even flourish in acidified conditions. This may be due to the complex nature of the seagrass, and high levels of photosynthesis, leading to local maintenance of pH microclimates. Secondly, the high degree of pH variability that naturally occurs in these shallow water habitats may result in organisms that are be better equipped to withstand pH variation. This research suggests that highly productive, non-calcifying, biogenic habitats, such as seagrass beds, may provide a refuge from OA, and highlights the importance of their conservation.

Control and management of brine disposal for inland desalination plants

Triplicate samples of Posidonia oceanica were randomly collected at 26 locations along the Balearic Islands (Mediterranean Sea) during the summers of 2005 and 2006. Roots were subjected to a surface-sterilization protocol prior to nucleic acid extraction. The nitrogenase was amplified by PCR using degenerate primers for nifH gene sequences. The PCR products were checked by electrophoresis on 1.5% agarose gels. The youngest leaf (free of epiphytes) of three shoots and three young rhizome fragments were dried at 60oC for 48 h and ground to a fine powder. All isotopic analyses were measured using standard elemental analyzer isotope ratio mass spectrometer (EA-IRMS) procedures. Isotopic ratios (R) are reported in the standard delta notation (‰), deltasample=1000((Rsample/Rstandard)-1), where R = 15N/14N. These results are presented with respect to the International standard of atmospheric nitrogen (AIR, N2). Analytical reproducibility of the reported delta values, based on sample replicates, was better than ±0.2‰.

The concentrations of Cd, Pb, Fe, Cr, Ni, Se, Sb, As and Cu were investigated in the nesting environment of green turtles in Mediterranean Sea near Kazanli, Mersin-Turkey. Tissues of plants growing on the beach and the adjacent environment, beach sand, sea ground sediment, sea grass as well as the egg shells from the nests were analyzed and the results showed no significant high levels of heavy metals detected. The higher levels of metals (Cr, Cu, Pb, Cd and As) were found in the samples from ground sea sediments. Ni and Sb were found at higher levels in river waters and Fe was at the highest in field soil. The high levels of Pb, Fe and Cd were also detected in sea grass, and the Cr, Cu and Ni in sea lily when comparison made with other plants. The levels of essential elements such as Fe and Cu were detected as the highest in most of the specimens. The herbivorous green turtles might be affected from the heavy metal concentrations in the future, since they feed on mainly sea grass. The accumulation of heavy metals via rivers into the sea might cause some pollution problems.

Schemes for salt recovery from seawater and RO brines using chemical precipitation