The fractionation of a protein hydrolysate obtained from tuna processing by-products by means of a membrane cascade integrating ultrafiltration (UF) and nanofiltration (NF) membranes was proposed in order to separate and purify the protein fraction between 1 and 4 kDa, which is the most interesting for nutraceutical purposes. A simulation model, based on mass balances and empirical equations for describing permeate flux and rejection of protein fractions, was developed and complemented with a simple cost estimation model. The product purity (49.3 %) and the process yield (62.6 %) were independent of the total water consumption of the process, but high water consumptions were required to maintain the total protein content of the stream below upper bounds that assured the absence of membrane clogging. The implementation of a water recovery system, based on an additional tight NF stage, implied improvements in both environmental and economic aspects of the process.

This work proposes the use of the life cycle assessment (LCA) to identify the best available techniques (BAT) to the management of the residues generated in the anchovy canning sector. This industry generates huge amount of solid and liquid wastes, and their management is one of the hotspots of the canned anchovy life cycle. The application of BATs can improve the environmental performance of the canned anchovy. However, sometimes it is not clear which BAT is the most appropriated, and an environmental analysis is required. In this sense, several BATs are proposed based on the circular economy concept, which promotes the reutilisation of wastes and they were evaluated under a life cycle approach: (i) valorisation of the anchovy residues into fishmeal, fish oil and anchovy paste, (ii) incineration and (iii) disposal in a municipal solid waste landfill. The LCA was conducted from cradle to gate using the global warming (GW) indicator. The results showed that the disposal of the anchovy residues in a landfill was the least environmental-friendly option, while the valorisation was the best alternative. | Authors thank to Ministry of Economy and Competitiveness of Spanish Government for the financial support through the project called GeSAC-Conserva: Sustainable Management of the Cantabrian Anchovies (CTM2013-43539-R). Jara Laso also thanks to the Ministry of Economy and Competitiveness of Spanish Government for the financial support through the research fellowship BES-2014-069368.

The chlor-alkali industry sector produces chlorine, sodium/potassium hydroxide and hydrogen by the electrolysis of brine. Nowadays, three different electrolysis techniques are applied: mercury, diaphragm, and membrane cell technology. From all these technologies, the European Commission labels the membrane process as the Best Available Technique (BAT) for the chlor-alkali industry. The membrane cell technology has fewer exhausts to the environment and it is relatively more efficient in the use of electric power that mercury and diaphragm. Nevertheless, despite the fact that the overall energy intensity has been reduced, the issue of energy consumption is still a major matter. A promising approach for reducing the electricity demand of chlor-alkali electrolysis is using oxygen-depolarised cathodes (ODC). ODCs are long known and have been successfully used in chlorine production through electrolysis of hydrogen chloride (HCl). The achieved environmental benefit of this technique is a reduction of energy consumption. However, the overall reduction of energy consumption is lower, as some energy is required to produce pure oxygen and because hydrogen is not co-produced, which could otherwise be used in chemical reactions or to produce steam and electricity via combustion or fuel cells. In this sense, the reduced electricity demand does not necessarily imply cleaner chlorine production. For that reason, this work proposes the use of the life cycle assessment (LCA) methodology to determine the environmental performance of the existing electrolysis technologies and to compare it with the ODC technique.

The study examined the individual and combined effects of potassium ferrate(VI) additions and freeze-thaw conditioning for the treatment and dewatering of sludge samples. The first part of the experiments, using primary sludge, compared potassium ferrate(VI) additions prior to freeze-thaw treatment (pretreatment) versus potassium ferrate(VI) additions following freeze-thaw treatment (posttreatment). A low dose (LD) of 1.0 g/L and a high dose (HD) of 10.0 g/L of potassium ferrate(VI) were evaluated along with a freezing temperature of −20 °C and freezing periods of 1, 8 and 15 days. Following the designated freezing period, the samples were removed from the freezer and thawed at room temperature for 12 h. The second part of the study, using anaerobically digested sludge, evaluated the effects of potassium ferrate(VI) pretreatment, using LD = 0.5 g/L and HD = 5.0 g/L, and used simulated drainage beds to separate meltwater from the sludge cake during the thawing period. The study demonstrated that stand-alone freeze-thaw can reduce faecal coliform by >3-log after being frozen for only 1 day, and pretreatment with potassium ferrate(VI) can be used to improve the effects of freeze-thaw on faecal coliform inactivation in sludge. Furthermore, the drainability of the sludge following freeze-thaw was not significantly deteriorated when potassium ferrate(VI) was added to the sludge prior to freezing, despite greater than fourfold increases in the concentrations of soluble proteins and soluble carbohydrates. The meltwater collected during the sludge thawing was approximately 85 % of the initial sludge volume. When 5 g/L of potassium ferrate(VI) was added to the sludge prior to freezing, the meltwater collected had <0.28 MPN/mL faecal coliform, the turbidity was <10 NTU and the pH was 9.1. Pretreatment with potassium ferrate(VI) also reduced the concentration of faecal coliform in the sludge cake, suggesting that freeze-thaw coupled with potassium ferrate(VI) additions can be used to stabilise sludge and reduce sludge volume.

Combined coagulation and electrochemical treatment processes were used to mineralize the organic load and detoxify a real textile effluent. The coagulation step was investigated for distinct pH values (4 to 11) and Al₂(SO₄)₃ concentrations (0.25 to 9.00 g L⁻¹). Complete turbidity and partial total organic carbon (TOC) removals were attained at pH 5, using 0.50 g L⁻¹Al₂(SO₄)₃. Moreover, the coagulation process totally removed the initial toxicity (100 % mortality) of the effluent, assessed by toxicity tests with the crustacean Artemia salina. The remaining TOC was mineralized by the electrochemical step in a flow cell with a boron-doped diamond (BDD) anode, when the investigated parameters were the BDD boron-doping level (100, 500, 2500 ppm), pH (3, 7, 11, no control), and current density (10, 20, 30 mA cm⁻²). No significant differences in TOC removal were observed when the BDD anode or pH value was changed; however, as the system was under mass transport limitation, mineralization attained at low current densities led to a reasonable current efficiency (∼40 %) and low energy consumption (∼16 kW h m⁻³). The use of the electrochemical method solely led to poor TOC and turbidity removals, thus not being recommended.

Natural organic matter (NOM) in groundwater is a factor of concern in long-term operation of Fe⁰ permeable reactive barrier (PRB). In this study, humic acid, a major component of NOM, showed dual effects in trichloroethylene (TCE) removal from simulated groundwater by Fe⁰ in batch and column experiments. In the initial stage of contacting with Fe⁰, humic acid promoted TCE removal due to its hydrophobic partitioning towards TCE and the subsequent fast adsorption onto Fe⁰ surfaces. In a long run, humic acid inhibited TCE removal because the buildup of adsorbed humic acid on Fe⁰ surfaces passivated Fe⁰ reactivity and limited TCE mass transfer. Ca²⁺ enhanced the co-aggregation of humic acid with Fe⁰ corrosion products and led to a faster depletion of TCE removal capacity by diminishing Fe⁰ matrix porosity. Revealed by FTIR analysis, part of TCE removed through hydrophobic partitioning was retained in humic acid accumulated on Fe⁰ surfaces rather than reductively degraded by Fe⁰. It raises a concern of using Fe⁰ PRB to treat organic contaminants in NOM-rich groundwater. Releasing back of NOM retained organic contaminants might take place once the accumulated NOM is desorbed or detached from Fe⁰ surfaces, resulting in a rebound of organic contaminants in the groundwater beyond the confine of PRB.

Volatile organic sulfur compounds (VOSCs) are frequently reported in eutrophic lakes during the process of algal blooms’ degradation. The algal-induced so-called black water blooms have been purported to be a big contributor to the production of VOSCs. However, the production mechanism of VOSCs in black water blooms and its influencing factors still remain unclear. In this study, a laboratory sediment/algal slurry experiment was carried out to investigate the formation process of black water blooms and factors such as temperature, microorganisms, and sulfate concentrations on the production of VOSCs in eutrophic lake sediments during the decomposition of algal blooms. The simulation study indicated that black water blooms can only be produced with the participation of sediment and algal together, which could be the result of low redox potential and the continuous release of ferrion irons (Fe²⁺) and hydrogen sulfide (H₂S) into the lake’s ecosystem; however, neither of algal nor sediment can induce the formation of black water blooms. In addition, the sediment + algal treatment can produce more VOSCs than a single sediment or algal treatment. Higher temperature incubation and a higher concentration of sulfate additions can enhance the concentration of H₂S and VOSCs in black water blooms. However, the addition of microbial inhibitors in the algal/sediment slurry indicated that sulfate reducing bacteria (SRB) can stimulate the production of VOSCs, whereas methanogen might consume some concentration of VOSCs and thus lower their concentration in black water blooms.

Agricultural drainage plays a vital role in the discharge of non-point source pollutants into surface-receiving waters. Sustainable drainage management to mitigate nitrogen losses from cultivated land is needed. Many factors influence nitrogen removal in agricultural drainage ditches. However, existing research has not fully considered parameter sensitivity analysis of nitrogen removal. Therefore, in this study, an ecological ditch model containing a permeable dam was built, in which the influent nitrogen concentration, suspended solid concentration, influent flow, and water level were examined as influencing factors. An orthogonal test was conducted to explore the significance of these four factors and their impacts on nitrogen removal as well as the nitrogen transport characteristics along the ditch. The results revealed that the ditches had an interception effect on nitrogen pollutants, and according to importance, the four factors are influent nitrogen concentration, water level, water flow, and suspended solid concentration in descending order. The plants and permeable dam in the ditch also played an important role in nitrogen removal.

Combination of active and thermally stable amino acid-functionalized ionic liquids (AAILs) with high surface area and porosity of mesocellular silica foams (MCF) to form a robust CO₂ sorbent is investigated in this study. These sorbent composites (MCF-x) are synthesized by immobilizing three AAILs (Gly, Lys, and Arg) into MCF by a simple wet-impregnation method. The prepared AAILs and MCF-x sorbents are characterized by N₂ adsorption/desorption, small-angle X-ray scattering (SAXS), elemental analysis (EA), and Fourier-transformed infrared (FTIR) spectroscopies. Their corresponding CO₂ sorption–desorption performance at 348 K under ambient pressure using dry 15 % CO₂ is also studied. The obtained results show that the AAILs have low CO₂ sorption capacities and rates because of their high viscosities. The MCF-x sorbents, however, exhibit remarkable enhancement of sorption capacities and fast kinetics. Among these sorbents, MCF-Lys possesses the superior sorption capacity of 1.38 mmolCO₂/gₛₒᵣbₑₙₜ, the higher tolerance to water moisture and much better long-term durability which may be a promising sorbent for CO₂ capture applications.

Mercury (Hg), aside from having high toxicity, is characterized by its ability to biomagnify in the marine trophic chain. This is an important problem especially in estuaries, or in the coastal zone, particularly near the mouths of large rivers. This study was conducted in the years 2001–2011, in the coastal zone of the Baltic Sea near to the mouth of the River Vistula, which is the second biggest river discharging into the Baltic. Mercury concentration was measured in the tissues and organs of cod, flounder, herring, seals (living in the wild and in captivity), great black-backed gulls, and African penguins from Gdańsk Zoo, and also in human hair. Penguins and seals at the seal sanctuary in Hel were fed only herring. In marine birds and mammals and in the pelagic herring, the highest Hg concentration was observed in the kidney and in the liver, while in cod and flounder (located on a higher trophic level) the muscles were the most contaminated with mercury. In gray seals living in the seal sanctuary, Hg concentration in all analyzed tissues and organs except the kidneys was lower in comparison with seals living in the wild. The comparatively small share of fish in the diet of local Polish people and their preference towards the consumption of herring contributed to low concentration of Hg in their hair. The protective mechanisms related to detoxification and elimination of mercury were shown to be more effective in the seals than in the penguins, despite the former consuming around 10 times more food per day.