Ramiro J.E. Martins

Uptake and release of zinc by aquatic bryophytes (Fontinalis antipyretica L. ex. Hedw.)

The zinc uptake and posterior release by an aquatic bryophyte-Fontinalis antipyretica L. Ex Hedw.--was experimentally studied in laboratory exposing the plants to different zinc concentrations in the range, 1.0-5.0 mg 1(-1), for a 144 h contamination period, and then exposed to metal-free water for a 120 h decontamination period. The experiments were carried out in perfectly mixed contactors at controlled illumination, using mosses picked out in February 1997, with a background initial zinc concentration of 263 mg g(-1) (dry wt.). A first-order mass transfer kinetic model was fitted to the experimental data to determine the uptake and release constants, k1 and k2, the zinc concentration in mosses at the end of the uptake period, C(mu), and at the equilibrium, for the contamination and decontamination stages, C(me) and C(mr), respectively. A bioconcentration factor, BCF = k1 /k2 (zinc concentration in the plant, dry wt./zinc concentration in the water) was determined. A biological elimination factor defined as BEF = 1 - C(mr)/C(mu) was also calculated. BCF decreases from about 4500 to 2950 as Zn concentration in water increases from 1.05 to 3.80mg 1(-1). BEF is approximately constant and equal to 0.80. Comparing Zn and Cu accumulation by Fontinalis antipyretica, it was concluded that the uptake rate for Zn (145 h(-1)) is much lower than for Cu (628 h(-1)) and the amount retained by the plant decreased by a factor of about seven.

Kinetic modelling of cadmium and lead removal by aquatic mosses

Because biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In the present study, the performance of the aquatic moss Fontinalis antipyretica for removing cadmium and lead from simulated wastewaters has been evaluated. Five kinetic models (first-order, pseudo-first-order, Elovich, modified Ritchie second-order and pseudo-second-order) were fitted to the experimental data and compared. Previously, the effect of parameters such as the initial solution pH, contact time, and initial metal ion concentration on biosorption was investigated. The initial pH of the solution was found to have an optimum value in the range of 4.0-6.0. The equilibrium sorption capacity of cadmium and lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg L-1, the uptake capacity of the moss, at equilibrium, is the same for both metals (4.8 mg g-1). Nevertheless, when the initial concentration increases up to 100 mg L-1, the uptake of Pb(II) was higher than 78%. The pseudo-second order biosorption kinetics provided the better correlation with the experimental data (R2 ≥ 0.999).

Chemical and Biological Treatment of Fish Canning Wastewaters

Abstract — The main environmental problems of fish canning industries are high water consumption and high organic matter, oil and grease and salt content in their wastewaters. This work aims to analyze the situation of different plants located north of Douro river, in Portugal, in order to propose various solutions to their problems. Thus, initially it was made an identification and implementation of prevent and control pollution measures within the industrial units in order to reduce water consumption, minimize the wastewater production and reduce the pollutant load to treat. Then, the wastewater treatability was evaluated through a sedimentation and coagulation-flocculation process and through an aerobic biological degradation. In the sedimentation and coagulation-flocculation process two organic coagulants (RIPOL 070 and RIFLOC 1815), commonly used in wastewater treatment, were tested, leading to good results, especially in terms of oil and grease and total suspended solids removals. The best suspended solids removal efficiencies were 53% and 79%, using 400 mg/L of RIPOL 070 and 150 mg/L of RIFLOC 1815, respectively. At these dosages, both coagulants demonstrated excellent oil and grease removals, about 99% for RIFLOC 1815 and 88% for RIPOL 070. The aerobic biological treatment with activated sludge proved to be very adequate to organic matter removal. Two feed flow rates were tested and the highest TOC removal efficiency (96%) was verified with the lowest one (0.75 L/h), corresponding to a longer hydraulic retention time (8 h). So, the proposed sequential treatment, combining physico-chemical and biological processes, proved to be an effective alternative to start the fish canning wastewaters treatment for further reuse in the industrial process.

Modelling of lead removal by an aquatic moss

Aquatic bryophytes are frequently used as biomonitors for trace metals in aquatic ecosystems. Nevertheless, their special characteristics also allow using them as biosorbents to clean industrial wastewaters. As biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In this study, the ability of the aquatic bryophyte Fontinalis antipyretica to remove lead from simulated wastewaters was evaluated. Three kinetic models (pseudo-first order, pseudo-second order and Elovich) were fitted to the experimental data and compared by the F-test. Previously, the effect on biosorption of parameters such as the initial solution pH, contact time and initial metal ion concentration was investigated. The initial pH of the solution was found to have an optimum value is in the range 4.0-6.0. The equilibrium sorption capacity of lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg L⁻¹, the uptake capacity at equilibrium was 4.8 mg g⁻¹. Nevertheless, when the initial concentration increased up to 100 mg L⁻¹, the uptake of lead was 10 times higher. The pseudo-second order biosorption kinetic model provided the better correlation with the experimental data (R²=1.00). The applicability of the Langmuir and Freundlich adsorption isotherms to the present system was also assessed. The maximum lead sorption capacity by Fontinalis antipyretica was 68 mg g⁻¹.

Cr(III) uptake by marine algal biomass: equilibrium and kinetics

In this work, biosorption of Cr(III) by the marine brown algae Sargassum muticum was studied in a batch system. Kinetics and equilibrium experiments were conducted at different pH. Equilibrium data are well described by the Langmuir and Langmuir-Freundlich isotherms. The two mass transfer models give comparable results, but they did not provide a perfect representation of the sorption data. Sargassum muticum was compared with the brown algae Laminaria hyperborean and the red algae Gelidium sesquipedale, showing maximum uptake capacities of, 56 ± 3, 70 ± 4 and 18 ± 1 mg Cr(III) g −1 , at pH = 5, respectively.

Pollution prevention and wastewater treatment in fish canning industries of Northern Portugal

High concentrations of particulate matter (PM) in the atmosphere have been associated with degradation of human health. Auckland is the most populous city in New Zealand, with a humid subtropical climate (characterised by hot and humid summers and mild winters) and is one of the most remote cities in the world. Analysis of the weather conditions and PM10 concentrations in Auckland can provide an understanding of how weather conditions impact PM10 concentrations in isolated systems. This study looks at the impacts of Temperature and Relative Humidity (RH) on localised PM10 concentrations in an urban area of Auckland over the winter period. This study has shown that the ratios of PM1:PM10 and PM2.5:PM10 were 64% and 87% over the study period. Temperature was observed to have a negative correlation with PM10 over a diurnal timescale. RH generally showed a positive correlation with PM10 up to a threshold value of 75% RH, beyond which the correlation ceased. RH affects the natural deposition process of PM, whereby moisture particles adhere to PM, accumulating atmospheric PM concentration. With increasing humidity, moisture particles eventually grow in size to a point where ‘dry deposition’ occurs, reducing PM10 concentrations in the atmosphere. There were a number of occasions where PM10 remained low even while RH increased and further investigation showed these events coincided with periods of rainfall.Soybean milk is a kind of highly perishable Asian traditional soy product, and this study was envisaged to extend its shelf-life through the application of hurdle technology. Twelve strains of bacteria were isolated from samples of spoilage soybean milk and were identified as Klebsiella oxytoca (S 5,S 7,S 8), Serratia marcescens (S 9, S 10,S 14, S 15, S 17), Klebsiella ozena (S 16, S 18), and Serratia plymuthica (S 21, S 25, S 28). To control these spoilage microorganisms, eight commonly used food preservatives were tested by Oxford Cup inhibition method. Results showed that sodium dehydroacetate, nipagin complex esters and nisin significantly inhibited the growth of the isolated strains with their MIC (minimum inhibition concentration) values ranging from 0.004% to 0.05%. Levels of heat treatment duration, together with concentrations of sodium dehydroacetate, nipagin complex esters, and nisin were employed as hurdle factors. The optimum conditions for improvement of the sshelf-life were gained from orthogonal tests as follows: heat treatment at 100°C for 10 minutes, and nisin 0.004%, nipagin complex esters 0.008%, dehydroacetate 0.002%. The fresh soybean milk applied with the optimum formula could be maintained under upper limit of the microbial count (100 CFU/mL, DB44/425-2007 China) for more than 6 days at 25°C, and 11 days at 4°C. Here in our study, hurdle technology approach significantly improved the shelf-life of soybean milk.The main environmental problems of fish canning industries are high water consumption and high organic matter, oil and grease and salt content in their wastewaters. This work aims to analyze the situation (water consumption, wastewater production, wastewater characterization, etc.) of different plants located north of Douro river, in Portugal, in order to propose various solutions to their problems. Thus, initially it was made an identification and implementation of prevent and control pollution measures within the industrial units in order to reduce water consumption, minimize the wastewater production and reduce the pollutant load to treat. Then, the evaluation of wastewater treatability was started through a sedimentation and coagulation-flocculation process, with two organic coagulants (RIPOL 070 and RIFLOC 1815), commonly used in wastewater treatment. Sedimentation experiments showed that the flotation of 54% of oils and greases occurred, and 36% of total suspended solids were removed. The coagulation-flocculation process gave good results, especially in terms of oil and grease and total suspended solids removal. The best suspended solids removal efficiencies were 53% and 79%, using 400 mg/L of RIPOL 070 and 150 mg/L of RIFLOC 1815, respectively. At these dosages, both coagulants demonstrated excellent oil and grease removals, about 99% for RIFLOC 1815 and 88% for RIPOL 070.Liana Dalcantara Ongouya Mouekouba, Zhen-Zhu Zhang, Erinle Kehinde Olajide, Ai-Jie Wang, and Ao-Xue Wang