Biosorptive removal and recovery of cobalt from aqueous systems

Equilibrium and kinetic aspects of cobalt biosorption onto a new biosorbent, PFB1, were studied. The biosorbent, PFB1, had a specific surface area of 256·8m²g⁻¹ and showed high equilibrium capacities for cobalt uptake, the highest being 190 mg g⁻¹, in the range of concentrations employed. The equilibrium uptake increased and then decreased with initial pH with the highest uptake at pH 7. The equilibrium uptake also decreased with increasing temperature in the range 30–45°C. The kinetics of cobalt uptake were analysed using mathematical models and the external mass transfer coefficient for cobalt biosorption on PFB1 was 0·075 m s⁻¹. EDAX and EPR studies indicated involvement of an ion-exchange mechanism and free-radical interaction in the biosorption process. Desorption/readsorption studies for three adsorption–desorption cycles were carried out with acidic, basic and salt desorbents and the highest desorption efficiencies of 92·5% and 70·5% at the end of the first and third cycles, respectively, were obtained with 0·1 N HCl as the desorbent.     

Biosorptive removal of cadmium from contaminated groundwater and industrial effluents

The cadmium removing capacity of a biosorbent Calotropis procera, a perennial wild plant, is reported here. The biomass was found to possess high uptake capacity of Cd(II). Adsorption was pH dependent and the maximum removal was obtained at two different pH i.e. pH 5.0 and 8.0. Maximum biosorption capacity in batch and column mode was found to be 40 and 50.5 mg/g. The adsorption equilibrium (> or =90% removal) was attained within 5 min irrespective of the cadmium ion concentration. Interfering ions viz. Zn(II), As(III), Fe(II), Ni(II) interfered only when their concentration was higher than the equimolar ratio. The Freundlich isotherm best explained the adsorption, yet the monolayer adsorption was also noted at lower concentrations of Cd(II). The FTIR analysis indicates the involvement of hydroxyl (-OH), alkanes (-CH), nitrite (-NO(2)), and carboxyl group (-COO) chelates in metal binding. The complete desorption of the cadmium was achieved by 0.1M H(2)SO(4) and 0.1M HCl. The C. procera based Cd(II) removal technology appears feasible.     

Nitrate removal from drinking water using a membrane-fixed biofilm reactor

Biological treatment of drinking water is a cost-effective alternative to conventional physico/chemical processes. A new concept was tested to overcome the main disadvantage of biological denitrification, the intensive post-treatment process to remove microorganisms and remnant carbon source. The biological reaction zone and carbon supply were separated from the raw water stream by a nitrate-permeable membrane. Denitrification takes place in a biofilm, which is immobilized at the membrane. In a series of bench-scale runs, different types of membranes and reactor configurations were investigated. The best denitrification rates achieved were 1230 mg NO₃ ⁻-N m⁻² day⁻¹. In one run, raw water containing 100 mg NO₃ ⁻ l⁻¹ was completely freed from nitrate. The membrane and the attached biofilm also represent a barrier against the passage of the C source and nutrients into the raw water. At concentrations of 20 mg l⁻¹ ethanol and 15 mg l⁻¹ phosphate in the bioreactor no diffusion through the membrane into the treated water was observed. Without any post-treatment, the effluent met nearly all the relevant criteria for drinking water; only the colony count was slightly increased. Received: 18 December 1996 / Received last revision: 14 April 1997 / Accepted: 19 April 1997     

Membrane bioreactors for the removal of anionic micropollutants from drinking water

Biological treatment processes allow for the effective elimination of anionic micropollutants from drinking water. However, special technologies have to be implemented to eliminate the target pollutants without changing water quality, either by adding new pollutants or removing essential water components. Some innovative technologies that combine the use of membranes with the biological degradation of ionic micropollutants in order to minimize the secondary contamination of treated water include pressure-driven membrane bioreactors, gas-transfer membrane bioreactors and ion exchange membrane bioreactors.     

Nitrate removal from drinking water in a fluidized-bed biological denitrification bioreactor

In most industrially developed countries an increasing degree of nitrification can be observed in potential water reservoirs. High nitrate content is unacceptable by public health standards. Since contamination seems to be unavoidable, the only realistic solution is purification prior to utilization. One of the potential variations is biological denitrification with a highly intensive facility, a fluidized- or expanded-bed bioreactor. Based on laboratory and pilot plant experiments, a detailed analysis is presented on the problems arising and solutions offered in the construction of a purification system meeting high quality requirements of drinking water purification. The crucial point is selection of the denitrifying microorganisms and organic matter required for denitrification, which simultaneously determines the attachment of bacteria to the support material (autoimmobilization), the intensity of nitrate removal and the character of post-purification.     

Relation between arsenic in drinking water and skin cancer

From observations in the Republic of Argentina it is concluded that the regular intake of drinking water containing more than 0.1 ppm of arsenic leads to clearly recognizable signs of intoxication and ultimately in some cases to skin cancer     

Al nanoclusters in coagulants and granulates: application in arsenic removal from water

The contamination of drinking and irrigation water by arsenic is a severe health risk to millions of people, particularly in developing countries. Arsenic treatment methods therefore need to advance to more durable and cost-effective solutions. In recent years, the unique properties of nanomaterials have received much attention in water treatment research, and their properties (e.g., high number of reactive surface binding sites) may make them suitable for arsenic removal. The aluminum nanoclusters Al₁₃ (AlO₄Al₁₂(OH)₂₄H₂O₁₂ ⁷⁺) and Al₃₀ (Al₂O₈Al₂₈(OH)₅₆(H₂O)₂₆ ¹⁸⁺) have high specific surface charge, deprotonate over a wide pH range and exhibit a high reactivity due to a great number of OH⁻ and H₂O groups. This contribution evaluates these chemical properties of aluminum nanoclusters and their efficiency for water treatment, particularly for arsenic removal. It assesses the advantages and constraints when applied in an industrially produced aluminum coagulant or in Al granulate during water treatment.     

Removal of fluoride, arsenic and coliform bacteria by modified homemade filter media from drinking water

An attempt was made to investigate the removal of fluoride, arsenic and coliform bacteria from drinking water using modified homemade filter media. Batch mode experimental study was conducted to test the efficiency of modified homemade filter for reduction of impurities under the operating condition of treatment time. The physico-chemical and biological analysis of water samples had been done before and after the treatment with filter media, using standard methods. Optimum operating treatment time was determined for maximum removal of these impurities by running the experiment for 2, 4, 6, 8, 10 and 12h, respectively. The maximum reduction of fluoride, arsenic and coliform bacteria in percentage was 85.60%, 93.07% and 100% and their residual values were 0.72 mg/l, 0.009 mg/l and 0 coliform cells/100ml, respectively after a treatment time of 10h. These residual values were under the permissible limits prescribed by WHO. Hence this could be a cheap, easy and an efficient technique for removal of fluoride, arsenic and coliform bacteria from drinking water.     

Effect of high arsenic content in drinking water on rat brain.

The permissible limit of arsenic content in drinking water is 0.05 ppm, whereas, in many parts of West Bengal the arsenic level in drinking water is 0.1 ppm, frequently 0.3 ppm and even 3.0 ppm, though rarely. In order to assess possible risk to brain function by drinking such water, rats were given arsenic mixed in drinking water at the above four concentrations for 40 days. There was increased lipid peroxidation at all doses of arsenic, including the 'permissible limit', decrease in glutathione level, superoxide dismutase and glutathione reductase activities, indicating the free-radical-mediated degeneration of brain.     

饮用水处理流程中的微藻及其去除率

为了解某市饮用水处理流程中的藻类状况,对某市饮用水源及自来水厂各主要处理过程中的水样进行藻类检测鉴定。在各水样中共检测到藻类72种,蓝藻、绿藻和硅藻为优势藻群,并检出微囊藻、颤藻和鱼腥藻等潜在产毒的种类,其中微囊藻在源水中的细胞密度为1.9×106cell·L-1。源水中藻类细胞密度为2.8×106cell·L-1,处理后自来水中藻类的细胞密度为4.6×104cell·L-1,藻类总去除率为98.3%,其中滤池对藻类的去除率为82.7%,但其对蓝藻的去除率仅为11.8%。研究结果表明,该市水源可能已受到藻毒素的污染;现有自来水处理工艺中的滤池难以对个体较小的有毒蓝藻有效去除。针对该地区水源藻类的分布情况提出了优化过滤工艺的建议。     

Characteristics of molybdate-impregnated chitosan beads (MICB) in terms of arsenic removal from water and the application of a MICB-packed column to remove arsenic from wastewater

The removal of arsenic (As) species, such as As(III) and As(V), from water by molybdate-impregnated chitosan beads (MICB) in both batch and continuous operations was studied. The effects of pH, temperature, coexisting ions, and arsenic concentrations were studied in batch tests. Studies on the kinetic adsorption of MICB, the recovery of arsenic by the desorption solution, and the reuse of MICB were also carried out. The practicality and efficiency of an MCIB-packed column on arsenic removal were evaluated in a continuous system on industrial arsenic-containing wastewater discharged during the manufacture of GaAs supports. The results indicate that MICB favor the adsorption of both As(V) and As(III). The optimal pH value for As(III) and As(V) removal was 5. The adsorption of arsenic on the MICB is most likely an exothermic reaction. The effect of coexisting ions was varied and depended on their concentrations and species. The optimal desorption solution for arsenic recovery was 1M H2SO4, which resulted in a 95% efficiency for As(III) and 99% for As(V). In the continuous tests, the MICB-packed column exhibited excellent arsenic removal from wastewater without any pretreatment. These results provide strong evidence of the potential of MICB for removing As from industrial wastewaters.     

Dehydrogenase activity of liver parenchyma in mice exposed to arsenic in drinking water.

The effect of arsenic administered in drinking water in the form of sodium arsenite in concentrations of 5,50 and 250 mg As-3+/1 on dehydrogenase activity (DHA) of liver parenchyma homogenate of exposed mice was studied. After an exposure lasting 2, 4, 8, 16, 32, and 64 days, 8--10 exposed mice and 5--10 animals of the control series were studied at each interval. DHA was determined by means of tetrazolium chloride reduction to formazan whose quantity was assessed spectrophotometrically after extraction with butanol. At a concentration of 5 mg A3+/1 a moderate increase in DHA was observed which was replaced by a moderate decrease at the following intervals. At a concentration of 250 mg A3+/1 a deep decrease in DHA (p smaller than 0.05) was recorded which did not return to values compararable with those of the control series in spite of its fluctuating increase in the course of exposure. At a concentration of 50 mg A3+/1 in drinking water ensuring the supply of doses which induce an increase in the tolerance to arsenic a decrease in DHA was found only at the first exposure interval. DHA is thus substantially less altered in comparison with the metabolic consumption of oxygen (MCO) under the same conditions. This finding signifies that MCO is a more sensitive indicator of arsenic exposure than DHA in the used arrangement of the experiment.     

Isolation of Legionella species from drinking water

Three different species of Legionella were recovered from samples of water taken from chlorinated public water supplies where no coliform bacteria were simultaneously detected. Five of 856 samples yielded Legionella isolates. Three isolates were identified as Legionella pneumophila serogroup 1, the fourth was identified as Legionella dumoffii, and the fifth was identified as Legionella jordanis. Studies to determine the survival of L. pneumophila Flint 1 serogroup 1 in tap water at various temperatures and in tap water with added sodium hypochlorite were done. These organisms were found to survive for 299 days in tap water at 24 and 5 degrees C but not at 35 degrees C. A concentration of at least 0.2 mg of residual chlorine per ml was required to eliminate at least 90% of L. pneumophila and Escherichia coli inocula in 2 h.     

Shifts in water quality in a drinking water reservoir during and after the removal of cyprinids

Lake ülemiste, the drinking water reservoir of Estonia’s capital city Tallinn, was biomanipulated by manual removal of cyprinids in 2004–2006 and its impact on water quality in the vegetation period was studied. A total biomass of 156 tonnes corresponding to 160 kg ha⁻¹ of fish, predominantly cyprinids, were removed. A decline in the unit catches of fishing was observed. The removed fish biomass versus phosphorus concentration of the lake was considered sufficient to reduce the impact of cyprinids on water quality. The phosphorus removed within fish biomass corresponded to 38 μg l⁻¹ and 21% of the external phosphorus load of the fishing period. The mean total phosphorus concentration dropped from >50 to ≤36 μg l⁻¹. However, the densities of planktivorous young-of-the-year percids remained high and the role of zooplankton grazing in improving water quality was found non-significant or transient. The cladocerans biomass decreased and the small-sized Daphnia cucullata remained almost the only daphnid in Lake ülemiste during and after the manipulation. Predomination of filamentous cyanobacteria was replaced by a more diverse phytoplankton composition and co-domination of micro- and pico-sized colonial cyanobacteria during summer. Mean phytoplankton biomass decreased from 15 to 6 mg l⁻¹ primarily as a result of decreased in-lake TP availability. The Secchi disc transparency increased only in May 2005–2007. The effects of coincidental events, a decline of external loading of phosphorus and a simultaneous flushing induced by heavy rainfall, on lake water quality are discussed with some implications to the future management of the reservoir.     

Sister-chromatid exchange (SCE) among individuals chronically exposed to arsenic in drinking water

A study was carried out on human subjects of various ages and backgrounds who had been drinking water containing more than 0.13 mg/l (0.13 ppm) arsenic for a period of at least 20 years. The main aim was not only to correlate the frequency of sister-chromatid exchanges in the lymphocytes with the amount of arsenic in water and urine but also to correlate the frequency of SCE with sex and age. In addition, family background regarding skin alterations or other arsenic-related symptoms was explored, so that individual health conditions could be assessed. External factors such as exposure to other chemical or contaminating agents (pesticides, battery manufacturing plants, foundries) were also taken into consideration. The data on sister-chromatid exchanges (282 exposed and 155 control individuals) showed that arsenic at concentrations used by our population (0.13 mg/l) induced a significantly elevated response. Other health effects of arsenic at these concentrations were found, e.g., hyperkeratosis, melanosis, actinic keratosis, basal cell carcinoma.