Water purification of dyes by ceramic membranes modified by pyrocarbon of carbonized polyisocyanate

Pyrocarbon modification of microfiltration ceramic membrane from aluminum oxide by carbonization of polyisocyanate has been carried out. The structure of pyrocarbon was regulated by means of water, glycerin and nickel chloride. Water of purified of dyes by pressure-driven method at the pressure in the range 0.5–1.1 MPa. The retention coefficient and specific capacity of modified membranes for direct scarlet varies respectively from 84.3 to 99.99% and from 0.8 to 32.5 dm³/(m²?h) and brilliant green—from 45 to 99.99% and from 2.5 to 8.8 dm³/(m²?h) and they are determined not only by working pressure, but the structure of pyrocarbon too.     

Transfer of counterions and diffusion of electrolyte in inorganic membranes modified by ion exchanger nanoparticles

Using the method of impedance spectroscopy we have investigated charge selectivity of macroporous inorganic membranes modified with nanoparticles of the inorganic ion exchanger—hydrated zirconium dioxide, which displays anion-exchange properties in an acid area. It has been found that transfer numbers of the SO₄ ^2? reach 0.81–0.9 at the H₂SO₄ concentration 10 mol · m^?3 and decrease as the acid concentration in solution goes down. It has also been found that modified membranes demonstrate a two-fold decrease of the diffusion coefficient of H₂SO₄ compared with a free solution. It has been shown that charge selectivity of the membrane improves as the amount of the ion exchanger in the matrix increases.     

Photo-reductive defluorination of perfluorooctanoic acid in water

Globally distributed and highly stable, perfluorooctanoic acid (PFOA) has prompted much concern regarding its accumulation in the natural environment and its threats to ecosystems. Therefore, it is desirable to develop an effective treatment against PFOA pollution. In this study, a photo-reduction method is developed and evaluated for the decomposition of perfluorooctanoic acid (PFOA) in aqueous phase with potassium iodide (KI) as a mediator. The experiment was conducted under 254 nm irradiation at room temperature and pH 9 under anaerobic conditions. Ultraviolet photolysis of iodide solutions led to the generation of hydrated electrons (e_aq⁻, E_aq/e°= −2.9 V), which contributed to the defluorination of PFOA. Defluorination was confirmed by fluoride release of 98%, indicating almost complete defluorination of PFOA. Kinetic analysis indicated that the PFOA decomposition fit the first-order model with a rate constant of 7.3 × 10⁻³ min⁻¹. Besides fluoride ions, additional intermediates identified and quantified include formic acid, acetic acid, and six short-chain perfluorocarboxylic acids (C1-C6). Furthermore, small amounts of CF₃H and C₂F₆ were also detected as reaction products by using GC/MS. With observation of the degradation products and verification via an isotopic labeling method, two major defluorination pathways of PFOA are proposed: direct cleavage of C-F bonds attacked by hydrated electrons as the nucleophile; and stepwise removal of CF₂ by UV irradiation and hydrolysis. This method was applied to the decomposition of PFOA in wastewater issued from a fluorochemical plant and proved to be effective.     

Lead concentration profiles in lead-210 dated Lake Ontario sediment cores

Lead concentrations were measured in sediment cores from four sites distributed among the three major sedimentary basins — Niagara, Mississauga and Rochester — of Lake Ontario for which sedimentation rates had been previously determined by ²¹⁰Pb dating.Around 90% of the total lead present in fine-grained surface sediments was removed by CH₃CO₂H/NH₂OH · HCl leaching, concentrations ranging from 137 μg/g in surface sections to a constant background of 12–13 μg/g at unpolluted depths. Lead-210 dating indicated that increases in lead concentrations commenced ca. 1850–1875 with 5, 10, 35 and 50% of the total “excess” lead inventory in the sediment column being assigned to the pre-1900 period and successive 25-year intervals during the 20th Century, respectively. Anthropogenic inputs of lead from such sources as the combustion of leaded gasoline and coal are responsible for these increases.About 10 μg/g lead remained in the sediment residue after leaching. The total natural lead flux to the sediments ranged from 0.4–1.3 μg/cm²/yr while “excess” lead of anthropogenic origin varied from 1.2–6.7 μg/cm²/yr and totalled 0.5–1.5 g/m² at the four sites.Various potential modes of introduction of anthropogenic lead and of ²¹⁰Pb to the lake are considered in conjunction with the ratio of Pb/²¹⁰Pb fluxes to the sediment.     

Photocatalytic Destruction of Fulvic Acids by Various Oxidants in a Reactor with Immobilized TiO<Subscript>2</Subscript>

Comparison of the efficiency of photocatalytic oxidation of aqueous solution of fulvic acids (TOC₀—15.9–17.1 mg/dm³, pH0 6 ± 0.1) by oxygen of the air, hydrogen peroxide and ozone in a reactor containing a wide-porous ceramic block with immobilized TiO₂ with the variation of the concentration of H₂O₂, feed rate of O₃ and temperature showed advantages of photocatalytic ozonization and expediency of its use for deep destruction of natural organic substances in water. The maximum degree of destruction in photocatalytic systems O₂/TiO₂/UV, H₂O₂/TiO₂/UV and O₃/TiO₂/UV constituted respectively 41, 73 and 90% for TOC for 5, 4 and 3 h.     

Modeling of coagulation-microfiltration hybrid process for treatment of oily wastewater using ceramic membranes

In this novel paper, fouling mechanisms of Mullite-alumina ceramic membranes in treatment of oily wastewaters in hybrid coagulation—microfiltration (MF) process have been presented. Hermia’s models for cross flow filtration were used to investigate the fouling mechanisms of membranes at different time intervals with various coagulant concentrations. Four coagulant ((ferrous chloride (FeCl₂ · 4H₂O), ferrous sulfate (FeSO₄ · 7H₂O), aluminum chloride (AlCl₃ · 6H₂O) and aluminum sulfate (Al₂(SO₄ ^?)₃ · 18H₂O)) plus equal concentration of calcium hydroxide in form of calcium hydroxide (Ca(OH)₂) were evaluated in the coagulation—MF hybrid process at different concentrations (0, 50, 100 and 200 ppm). To determine whether the data agree with any of the considered models, the coefficient of determination (R₂) of each plot for one model was compared with the others. In addition, average prediction errors of models are calculated. The results showed that the cake filtration model can be applied for prediction of the permeation flux decline for MF and coagulation—MF hybrid process with the best and worst average error equal to 0.96% and 5.78% respectively. Results indicated that by increasing time in filtration pore blocking behavior changes and one model cannot predict pore blocking behavior in all filtration time with very good preciseness.     

Defluorination of natural waters by filtration through glauconite treated with aluminum salts

It is shown that the use of glauconite modified by the aluminum layers makes it possible to reduce the content of fluoride-ions to the MAC level. Optimal conditions of modification have been established: pH 4–5, C_Al ³⁺-0.15–0.2 mg/dm³. For obtaining high-quality water from underground waters a mixed medium of natural and modified forms of glauconite may be used.     

Trihalomethanes in the drinking water of Concepción and Talcahuano,Chile

Formation of trihalomethanes (THMs) during water disinfection has been related to several health problems, although the magnitude of these effects is under discussion. This paper quantifies the THMs in drinking water from the Bío‐Bío Region of central Chile, the first since the modification of the national reference value (Nch 409/05) to include maximal values for THMs. THMs were quantified using a solid phase micro‐extraction (SPME) method and GC‐MS. The concentration ranges were 9.7–111.6, 0.1–1.0 and 0.9–25.5 μg/L for chloroform (CHCl₃), and dibromochloromethane (CHClBr₂) and bromodichloromethane (CHCl₂Br), respectively. Bromoform was not detected in any sample. There were good correlations (R²=0.91–0.98, P<0.001) between the THMs and the residence time of the water, the distance from the treatment plant and an inverse correlation to free chlorine in the water. The Additive Toxicity Index Value (0.07–1.00) showed that all samples were within the Chilean reference value for THMs in drinking water. However, several values were close to exceeding the maximum permitted concentration (200, 100, 100 and 60 μg/L for CHCl₃, CHBr₃, CHClBr₂ and CHCl₂Br, respectively), which may occur when the water demand is low and thus residence times are longer.     

Water purification of dyes by ceramic membrane modified by pyrocarbon from carbonized polymers

Modification of membranes by pyrocarbon was carried out by carbonization of polyisocyanate, celluloacetate and Na-salt of carboxylmethyl cellulose at 750°C. The water was purified of dyes by the pressure-driven method under pressure from 0.1 to 1.1 MPa. The retention coefficient and specific capacity of modified membranes for direct scarlet vary respectively from 37 to 99.99% and from 1.8 to 36 dm³/(m² ? h). For membranes with carbonized cellulose ethers the retention rate for brilliant green vary from 19 to 78.5% and the specific capacity depending on pressure and filtration time varies from 8.1 dm³/(m² ? h) to ~ 1 m³/(m² ? h).     

Performance and Morphology Evaluation of Thin Film Composite Polyacrylonitrile/Polyamide Nanofiltration Membranes Considering the Reaction Time

Polyacrylonitrile/polyamide (PAN/PA) thin film composite nanofiltration membranes were manufactured by interfacial polymerization (IP) of trimesoylchloride reacting with piperazine, in the presence of triethylamine. The influence of IP reaction time up to 100 s on the membrane performance and structure was investigated considering flux, rejection, structural morphology and roughness of the membrane using permeation test, scanning electron microscopy, atomic force microscopy as well as fourier transform infrared spectroscopy. Structural evaluation of membranes revealed that the average PA surface pore size was reduced initially up to 60 s of reaction due to the crosslinking process and PA layer compaction increment, however, became larger at longer reaction times. The PA layer effective thickness grew up with IP time and became constant after 60 s. The best water flux and Na₂SO₄ salt rejection were obtained at 60 s of reaction, which were 100 m³/day and 87% at pressure of 13 barg. Variation trends of permeation and morphological results showed accordance that confirmed their accuracy. Comparison of the Na⁺ rejection value with the rejection of commercialized NF membrane of Dow Company (NF90–400/34i) showed acceptable result for membrane performance.     

Extraction of zinc from aqueous solutions by electrically polarized cation exchange fibers

The process of treating galvanizing bath rinsing water by electrodialysis method with dialysate chamber filled with Fiban-K cation exchange fiber was investigated. The relationship between electromigration of zinc ions and electric current density was shown to have a maximum value within a range of 8–12 mA/cm². Within this range the electromigration flow of zinc ions in the presence of ion exchange fiber increases by ～20%, transport of hydrogen ions reaches 11.3% of the total flow of cations, residual concentration of zinc ions in dialysate in quasi-stationary mode at a current density of >10 mA/cm² does not exceed 2–4 mg/dm³, and without chamber loaded—10–15 mg/dm³.     

Tobacco ore of the Kerch iron-ore basin as a sorbent for removing <Superscript>90</Superscript>Sr from water medium

The paper investigates sorption removal of ⁹⁰Sr from water media by the tobacco ore of the Kerch iron-ore basin. It has been found that effective sorption is observed within the pH interval 6–9, the limit value of adsorption of strontium ions calculate by means of the Langmuir equation constitutes 17.95 mg/g. It is shown that sorbent efficiency for the removal of ⁹⁰Sr from water is determined, in the first place, by their salt composition—nature of macrocomponents characteristic for water media (Na⁺, K⁺ and Ca²⁺) and their concentration.     

Performance analysis of a full-scale duckweed-covered sewage lagoon

A sewage lagoon for 2000–3000 capita (0.6 ha) has been operated successfully with a duckweed cover for over four years. The cover suppressed algal growth; the effluent turbidity was always below 12 Ntu. Because of inappropriate construction, one fifth of the inflow is lost by percolation and seepage during the dry season; during the wet season the loss is limited. During a detailed sampling period in the dry season actual hydraulic retention time was 20.4 d, and surface loading rate was 48–60 kgBOD₅/ha · d. Concentration reduction was 90–97% for COD, 95–99% for BOD₅, and 74–77% for Kjeldahl-N and total P. Effluent contained 2.7 mg Kjeldahl-N/l and 0.4 mg total P/l. The water column remained aerobic. At two-thirds of retention time the plants had absorbed virtually all NH⁺₄ and ortho-PO³⁻₄ from the water column. The duckweed harvest would remove in a watertight lagoon 60–80% of the N and P load, or 0.26 gN/m² · d and 0.05 gP/m² · d (in the first three-quarters of retention time). The results during this period were representative for the 4-year operation so far. Corrected for the leakage, plant productivity under these fertilised and managed conditions was sustained for several years at the level of 58–105 kg(dw)/ha · d, or 715–1200 kg/ha · d (over full lagoon surface) in the dry and wet season, respectively. We suggest that the microbial hydrolysis of the more complex organic N and P into NH⁺₄ and ortho-PO³⁻₄ is the limiting step for enhanced biomass production.     

Electrochemical degradation of perfluorooctanoic acid (PFOA) by Ti/SnO2-Sb, Ti/SnO2-Sb/PbO2 and Ti/SnO2-Sb/MnO2 anodes

Electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) in aqueous solution was investigated over Ti/SnO₂-Sb, Ti/SnO₂-Sb/PbO₂, and Ti/SnO₂-Sb/MnO₂ anodes. The degradation of PFOA followed pseudo-first-order kinetics. The degradation ratios on Ti/SnO₂-Sb, Ti/SnO₂-Sb/PbO₂, and Ti/SnO₂-Sb/MnO₂ anodes achieved 90.3%, 91.1%, and 31.7%, respectively, after 90 min electrolysis at an initial 100 mg/L PFOA concentration at a constant current density of 10 mA/cm² with a 10 mmol/L NaClO₄ supporting electrolyte solution. The defluorination rates of PFOA on these three anodes were 72.9%, 77.4%, 45.6%, respectively. The main influencing factors on electrochemical decomposition of PFOA over Ti/SnO₂-Sb anode were evaluated, including current density (5-40 mA/cm²), initial pH value (3-11), plate distance (0.5-2.0 cm), and initial concentration (5-500 mg/L). The results indicated that PFOA (100 mL of 100 mg/L) degradation ratio and defluorination ratio achieved 98.8% and 73.9%, respectively, at the optimal conditions after 90 min electrolysis. Under this optimal condition, the degradation rate constant and the degradation half-life were 0.064 min⁻¹ and 10.8 min, respectively. The intermediate products including short-chain perfluorinated carboxylic acids (PFCAs, C₂∼C₆) and perfluorocarbons (C₂∼C₇) were detected by electrospray ionization (ESI) mass spectrum. A possible electrochemical degradation mechanism of PFOA including electron transfer, Kolbe decarboxylation, radical reaction, decomposition, and hydrolysis was proposed. The electrochemical technique could be employed to degrade PFOA from contaminated wastewater as well as to reduce the toxicity of PFOA.     

Assessment of wastewater pollution in pig leather industry in China

Pig leather industry contributed significantly to the life of people all over the world, but serious water environmental problems have arisen. Investigation in tanneries with green pig hides in China showed that pollution resulted mainly from beamhouse operations. Assessment indicated that wastewater from pig‐hides processing had: (1) wide variations of pH, (2) high levels of sulfide (S^2?) and chromium, (3) high levels of neutral salts and ammonia nitrogen (NH ₄⁺‐N), (4) high levels of suspended solids (TSS) and oil & grease, and (5) low biodegradability. A tannery processing 10 000 pig hides per day generated chemical oxygen demand (COD) of 3.81–12.31 tonnes and NH ₄⁺‐N 0.27–1.06 tonnes, respectively. The pollution loads were equivalent to those of a city of 60 000–120 000 inhabitants, which has a COD of 3.9–10.56 tonnes/day and NH ₄⁺‐N of 0.462–1.164 tonnes/day, respectively (SEPAC). And nearly 30% of the tanneries discharged their wastewater by screening only or by primary treatment like coagulation–sedimentation, while the rest of them discharged directly into surface waters without any treatment.     

Ozone oxidation for the alleviation of membrane fouling by natural organic matter: A review

Membrane fouling by natural organic matter is one of the main problems that slow down the application of membrane technology in water treatment. O₃ is able to efficiently change the physico-chemical characteristics of natural organic matter in order to reduce membrane fouling. This paper presents the state-of-the-art knowledge of the reaction mechanisms between natural organic matter and molecular O₃ or OH radicals, together with an in-depth discussion of the interactions between natural organic matter and membranes that govern membrane fouling, inclusive the effect of O₃ oxidation on it.     

Detection,occurrence, and removal of selected pharmaceuticals in Missouri source and finished drinking waters

A simple, sensitive, and selective solid phase extraction – ultra-fast liquid chromatography – tandem mass spectrometry (SPE-UFLC-MS/MS) method was developed and applied for the analysis of selected important pharmaceutical compounds in source and finished drinking waters. The method detected the following six pharmaceuticals, cotinine, cephapirin, ciprofloxacin, enrofloxacein, azithromycin, and diphenhydramine, at sub-μg/L level in multiple water matrices after pre-concentration by SPE. Cotinine-d₃ and ¹³C₃¹⁵ N-Ciprofloxacin were used as internal standards for accurate quantitation. This method was validated through spike recoveries (67–129%), reproducibility (RSD: 2.3–15.7%), and method detection limits (MDLs: 2–5 ng/L). The method was used to test for occurrence of these pharmaceuticals in source and drinking waters from 13 Missouri water treatment facilities in four different seasons. In general, higher detection frequency and concentrations of pharmaceuticals were observed in colder months due presumably to less dilution (at lower flows) and slower degradation. The PPCP removals by different activated carbons were also evaluated. The occurrence and removal results in this study provide valuable information to help water treatment facilities taking appropriate strategies for better control of trace pharmaceuticals in drinking water.     

Three-dimensional geotechnical modeling of the soils in Riyadh city,KSA

A standard penetration test (SPT) was carried out for 700 samples from 143 boreholes in four districts in Riyadh city, Kingdom of Saudi Arabia (KSA). Rock quality designation (RQD) and unconfined compression strength (UCS) tests were also performed for 238 samples from 154 boreholes in 15 districts of the city. Three-dimensional (3D) models of the SPT, RQD, and UCS were produced using the Voxler 3 software package. Further, 333 soil samples collected from 106 boreholes in 11 districts were examined to spatially model the distinctive geotechnical patterns of the alluvial soils in two dimensions. Tests were carried out to determine the soil grain size distribution, natural water content (NWC%), Atterberg’s consistency limits [liquid limit (LL%), plastic limit (PL%), and plasticity index (PI%)], and soil–water chemical components (pH Cl⁻, SO₃²⁻, and CO₃⁻). Spatial maps of the geotechnical parameters were produced by applying the geostatistical ordinary kriging implemented in ArcGIS. Soil samples were classified according to the unified soil classification system (USCS), and a thickness of the silty clay layer was produced. Plasticity charts indicated that the soils are inorganic cohesive clays with low and moderate plasticity (CL). Soil strength parameters showed wide ranges of UCS (average 220, range 21.3–618 kg/cm²), SPT (average 39, 0–100 N), and RQD (average 44, 11–78%). UCS and SPT 3D models clarified a regional southeastward trend of increase. RQD 3D models showed poor to fair engineering quality of rocks (25–75%). The results presented here can help to establish geohazard zonation maps with construction favorability ratings for safe urban expansion.

     

Water generation from atmospheric air by using different composite desiccant materials

In this communication, new composite desiccant materials having 37% concentration of CaCl₂ have been compared for water production from atmospheric air. The vermiculite–saw wood, jute and burnt-clay have been used as host materials and CaCl₂ as a hygroscopic salt. All the desiccant materials have been tested with the solar glass desiccant box type system (SGDBS) with a collector area of 0.36?m². Design parameters for water production are: height of the glass from the desiccant bed to be 0.22?m, an inclination angle of 30°, the effective thickness of the glass as 3?mm and the number of glazing is single. It has been found that on the experimental day, the maximum amount of fresh water generated by the vermiculite–saw wood/CaCl₂ is 130?ml/kg/day.     

Effect of Organic Carbon on Tertiary Denitrification of the Secondary Effluent in Biofilters Packed with Suspended Carriers

Denitrifying biokinetics in biofilters packed with suspended carriers were evaluated under different empty bed residence times (EBRT) with ethanol or acetate as the electron donor. The two denitrifying biofilters removed nitrate (NO₃^––N) effectively after only 3–4 days operation. At EBRT of 30; 15 and 7.5 min, the NO₃^––N removal percentage was 84; 72 and 59% in the ethanol biofilter, and was 89; 70 and 62% in the acetate biofilter, respectively. With the influent NO₃^––N loading rate ranged from 0.4 to 1.8 g/(m²·d), the NO₃^––N removal loading rate increased with increasing influent NO₃^––N loading rates, and the system was substrate limited. While when the influent nitrate loading rate was above 3 g/(m²·d), the system was biomass limited. The half-order coefficients were 0.162; 0.175 and 0.274 (mg/L)^1/2/min for the ethanol biofilter with the influent NO₃^––N concentration of 7.3–7.7 mg/L, and were 0.107; 0.165 and 0.303 (mg/L)^1/2/min for the acetate biofilter with the influent NO₃^––N concentration of 6.8–8.0 mg/L. Denitrification efficiency varied slightly during the backwashing cycle, and the effect of backwashing on the effluent turbidity was relatively large, especially for the biofilter with ethanol as the organic carbon.