Occurrence, oral exposure and risk assessment of volatile organic compounds in drinking water for Izmir

Concentrations of volatile organic compounds (VOCs) were measured in the drinking water in Province of Izmir, Turkey, and associated health risks due to ingestion of these compounds were investigated using population weighted random samples. A total of 100 houses were visited in different districts of Izmir and drinking water samples were collected from consumers' drinking water source. Questionnaires were administered to one participant in each house to determine demographics and drinking water consumption rates. Oral exposure and risks were estimated for each participant and Izmir population by deterministic and probabilistic approaches, respectively. The four trihalomethane (THM) species (i.e., chloroform, bromodichloromethane, dibromochloromethane, and bromoform), benzene, toluene, p-xylene, and naphthalene were the most frequently detected VOCs with concentrations ranging from below detection limit to 35 microg/l. The risk estimates were found to be less than the values reported in the literature with few exceptions. Noncarcinogenic risks attributable to ingestion of VOCs for Izmir population were negligible, whereas the mean carcinogenic risk estimates for bromodichloromethane and dibromochloromethane were above the de minimis level of one in a million (10(-6)). For all VOCs, the concentrations measured in metropolitan area were greater than those in other districts. All THM species were detected in higher concentrations in tap water, whereas nontap water contained more benzene, toluene, p-xylene, and naphthalene. Therefore, the concentrations of the latter four compounds and associated risks increased with increasing income and education level since bottled water was used in larger proportions within these subgroups. The results of this study showed that oral exposure to drinking water contaminants and associated risks may be higher than the acceptable levels even if the concentrations fall below the standards.     

Classification of organic and conventional olives using convolutional neural networks

Neural Computing and Applications - This paper presents a convolutional neural network (CNN) to classify between the conventionally and organically cultivated Memecik varieties of green olives. The...     

Indigenous peoples’ fisheries and food security: a case from northern Canada

Indigenous peoples in northern Canada (at least the off-reserve part of the population) experience food insecurity at a rate which is more than double that of all Canadian households. The Cree community of Norway House in northern Manitoba, which harvests and consumes a great deal of fish, may be an exception and may offer some lessons. The objective of the paper is to address food security through the lens of local fisheries, both commercial and subsistence, of a northern indigenous community, and to develop an integrated approach to analyze food security. The approach uses Sen’s entitlement theory and the concept of food sovereignty. This mixed-methods research study employed questionnaire surveys among on–reserve commercial and subsistence fishing households, semi-structured interviews, focus group discussions and follow-up interviews for verification. During commercial fishing seasons (spring/summer and fall), fishers and their helpers share their fish harvest extensively through their families and communal networks, reaching almost half of the total population of the community. Such extensive sharing and the continuing community-based fishery have contributed to Norway House having more than 90 % food secure households, comparable to the Canadian average. Norway House may provide an example for other northern indigenous communities regarding food insecurity through use of fish and other traditional foods. The proposed integrated approach may be useful for analyzing food security in general.     

Modelling of hydrogen cyanide formation in room fires

A chemical kinetics model for calculation of the formation of hydrogen cyanide (HCN) has been made. The combustion of a mixture of methylamine and ethylene has been modelled using the stationary laminar flamelet concept. The flamelet calculations are based on several thousand elementary reaction steps including the chemical kinetics of HCN in combustion. The flamelets for both cold (293 K) and hot (1000 K) combustion product recycling have been calculated. The effect of strain is also included in the flamelet calculations. Scalar dissipation rates from 0.01 s⁻¹ to extinction values have been varied. Also the effect of radiation is included in the flamelet state relationships.

Separate flamelet sets for various levels of radiation, from adiabatic up to 30% radiation losses, incremented by 1%, have been made. In the flow field calculation, the flamelet options may be used either as adiabatic, constant radiation or an interpolation between flamelet sets of different radiation.

The chemical kinetics model, incorporated into a Reynolds-Averaging Navier–Stoke (RANS) type CFD code, has been used to simulate two laboratory fire tests of the combustion of nylon. Changing the size of the opening in the test room varied the ventilation between the two tests. Flamelet sets for a mixture of methylamine and ethylene with nitrogen content close to that of nylon were used in these simulations. The simulations were made with and without recycling the combustion products back to the fire.

The calculations show that recycling of the combustion products to the fire increases the formation of HCN and CO. Similarly, a lowered ventilation rate increases the formation of these species. The calculated temperatures and main species concentrations, including HCN, agree reasonably well with the trends in the laboratory measurements.     

Mathematical modeling of copper(II) ion inhibition on COD removal in an activated sludge unit

A mathematical model was developed to describe the Cu(II) ion inhibition on chemical oxygen demand (COD) removal from synthetic wastewater containing 15 mg l(-1) Cu(II) in an activated sludge unit. Experimental data obtained at different sludge ages (5-30 days) and hydraulic residence times (HRT) (5-25 h) were used to determine the kinetic, stoichiometric and inhibition constants for the COD removal rate in the presence and absence of Cu(II) ions. The inhibition pattern was identified as non-competitive, since Cu(II) ion inhibitions were observed both on maximum specific substrate removal rate (k) and on the saturation constant (Ks) with the inhibition constants of 97 and 18 mg l(-1), respectively, indicating more pronounced inhibition on Ks. The growth yield coefficient (Y) decreased and the death rate constant (b) increased in the presence of Cu(II) ions due to copper ion toxicity on microbial growth with inhibition constants of 29 and 200 mg l(-1), respectively indicating more effective inhibition on the growth yield coefficient or higher maintenance requirements. The mathematical model with the predetermined kinetic constants was able to predict the system performance reasonably well especially at high HRT operations.     

The use of sulphuric acid-carbonization products of sugar beet pulp in Cr(VI) removal

A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas formed during carbonization process have been studied for Cr(VI) removal from aqueous solutions. The SO(2) rich gas was shown to be an excellent Cr(VI) reductant. The equilibrium and kinetic studies were conducted by using the carbonaceous adsorbent derived from sugar beet pulp. The lower pH favoured Cr(VI) adsorption but substantial Cr(VI) reduction was observed. The Langmuir and Freundlich isotherm models were applied and the Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacity of chromium calculated from Langmuir isotherm is about 24 mgg(-1) for 25 degrees C. The adsorption of Cr(VI) is an endothermic process and follows the pseudo-second-order rate kinetics. The sulphuric acid-carbonization is an economical method for particularly chromium removal because the gas generated during carbonization exhibits good Cr(VI) reduction properties and carbonaceous material obtained is an efficient Cr(VI) adsorbent.     

Performance of a hybrid-loop bioreactor system in biological treatment of 2,4,6-tri-chlorophenol containing synthetic wastewater: effects of hydraulic residence time

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with effluent recycle was used for biological treatment of 2,4,6-tri-chlorophenol (TCP) containing synthetic wastewater. Effects of hydraulic residence time (HRT) on COD, TCP and toxicity removal performance of the reactor were investigated for the HRT values between 5 and 30 h, while the feed COD (2700+/-100 mgl(-1)), TCP (300+/-10 mgl(-1)) and the solids retention time (sludge age, SRT, 20 d) were constant. Percent TCP, COD and toxicity removals increased with increasing HRT resulting in more than 90% COD, TCP and toxicity removals at HRT values above 25 h. Biomass concentrations in the packed column and in the aeration tank increased with increasing HRT resulting in low reactor TCP concentrations and therefore high TCP, COD and toxicity removals at high HRT values. Volumetric and specific rates of TCP and COD removals decreased with increasing HRT due to increased biomass and decreased flow rates at high HRT levels. Volumetric and specific removal rates of COD and TCP were maximum at an HRT of 5 h.     

Mathematical modelling of 4-chlorophenol inhibition on COD and 4-chlorophenol removals in an activated sludge unit

A mathematical model was developed for an activated sludge unit treating 4-chlorophenol (4-CP) containing synthetic wastewater composed of diluted molasses, urea, KH(2)PO(4) and MgSO(4) with COD and 4-CP contents of 2500 and 500 mg l(-1), respectively. The model included 4-CP inhibition on COD and 4-CP removals. Experimental data obtained at different hydraulic residence times (HRT=5-30h) and sludge ages (SRT, 3-30 days) were used to estimate the kinetic and inhibition constants for COD and 4-CP removal rates. 4-CP inhibition on COD removal was negligible while the inhibition on 4-CP removal was significant. The specific rate constant (k), saturation constant (K(s)) for COD oxidation were found to be 2.64 day(-1) and 559 mg l(-1), respectively. A similar model was used for 4-CP oxidation in the activated sludge unit and the constants were found to be k'=1.44 day(-1), K'(s)=25.7 mgl(-1), K"(CP)=559 mg l(-1),and K(I,CP)=17 mg l(-1). Increases in death rate constant because of 4-CP inhibition was also quantified and the inhibition constants were determined for both COD and 4-CP removals. Model predictions with the estimated kinetic constants were in good agreement with the experimental data. Developed model can be used to estimate the performance of an activated sludge unit treating 4-CP containing wastewater under the specified experimental conditions.     

Elimination of Cu(II) toxicity by powdered waste sludge (PWS) addition to an activated sludge unit treating Cu(II) containing synthetic wastewater

Copper(II) ion toxicity onto activated sludge organisms was eliminated by addition of powdered waste sludge (PWS) to the feed wastewater for removal of Cu(II) ions by biosorption before biological treatment. The synthetic feed wastewater containing 14 or 22 mgl(-1) Cu(II) was mixed with PWS in a mixing tank where Cu(II) ions were adsorbed onto PWS and the mixture was fed to a sedimentation tank to separate Cu(II) containing PWS from the feed wastewater. The activated sludge unit fed with the effluent of the sedimentation tank was operated at a hydraulic residence time (HRT) of 10h and sludge age (SRT) of 10 days. To investigate Cu(II), COD and toxicity removal performance of the activated sludge unit at different PWS loadings, the system was operated at different PWS loading rates (0.1-1 gPWSh(-1)) while the Cu(II) loading rate was constant throughout the operation. Percent copper, COD and toxicity removals increased with increasing PWS loading rate due to increased adsorption of Cu(II) onto PWS yielding low Cu(II) contents in the feed. Biomass concentration in the aeration tank increased and the sludge volume index (SVI) decreased with increasing PWS loading rate due to elimination of Cu(II) from the feed wastewater by PWS addition. PWS addition to the Cu(II) containing wastewater was proven to be effective for removal of Cu(II) by biosorption before biological treatment. Approximately, 1 gPWSh(-1) should be added for 28 mgCuh(-1) loading rate for complete removal of Cu(II) from the feed wastewater to obtain high COD removals in the activated sludge unit.     

Hydrogen gas production from vinegar fermentation wastewater by electro-hydrolysis: Effects of initial COD content

Vinegar fermentation wastewater with different initial COD contents (9.66–48.6 g L⁻¹) were used for hydrogen gas production with simultaneous COD removal by electro-hydrolysis. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (3197 ml), hydrogen yield (2766 ml H₂ g⁻¹ COD), hydrogen formation rate (799 ml d⁻¹), and percent hydrogen (99.5%) in the gas phase were obtained with the highest initial COD of 48.6 g COD L⁻¹. The highest energy efficiency (48%) was obtained with the lowest COD content of 9.66 g L⁻¹. Hydrogen gas production by water electrolysis was less than 250 ml and wastewater control resulted in less than 25 ml H₂ in 96 h. The highest (12%) percent COD removal was obtained with the lowest COD content. Hydrogen gas was produced by reaction of (H⁺) ions present in raw WW ( pH = 3.0) and protons released from acetic acid with electrons provided by electrical current. Electro-hydrolysis of vinegar wastewater was proven to be an effective method of H₂ gas production with some COD removal.