Slaughterhouse waste water (SHW) is discarded as unused disposals into the environment every day. The objective of the present study is to explore the possibility on the utilization of SHW for the preparation of culture media to produce mosquitocidal bacterium (Bacillus thuringiensis subsp. israelensis). This would help to overcome the problem of dumping SHW in to environment. A judicial combination of SHW with a mineral salt (MnCl2) was made to produce an enhanced level of bacterial production when compared with other culture media including conventional medium (Luria Bertani, LB). A complete degradation of SHW by the bacteria was observed. The biomass yield, bacterial growth, toxin production, and larvicidal activity against mosquito vectors were satisfactory. Cell mass yield of 4.55 gm l−1 (dry wt) and larvicidal activity of 0.006 mg ml−1 and 0.026 mg ml−1 at LC50 and LC90 levels were observed, respectively, against the filarial vector of Culex quinquefasciatus with bacteria grown in SHW + MnCl2. The B. thuringiensis subsp. israelensis also controlled the larvae in the field significantly for three weeks (>90% mortality) and the effect was comparable with LB. Cost-analysis for production of B. thuringiensis subsp. israelensis showed that it is more economical. Thus, this study suggested the dual benefit of efficient production of mosquitocidal toxin and management of slaughterhouse wastewater.

Clogging is the main operational problem associated with horizontal subsurface flow constructed wetlands (HSSF CWs). The measurement of saturated hydraulic conductivity has proven to be a suitable technique to assess clogging within HSSF CWs. The vertical and horizontal distribution of hydraulic conductivity was assessed in two full-scale HSSF CWs by using two different in situ permeameter methods (falling head (FH) and constant head (CH) methods). Horizontal hydraulic conductivity profiles showed that both methods are correlated by a power function (FH = CH0.7821, r 2 = 0.76) within the recorded range of hydraulic conductivities (0–70 m/day). However, the FH method provided lower values of hydraulic conductivity than the CH method (one to three times lower). Despite discrepancies between the magnitudes of reported readings, the relative distribution of clogging obtained via both methods was similar. Therefore, both methods are useful when exploring the general distribution of clogging and, specially, the assessment of clogged areas originated from preferential flow paths within full-scale HSSF CWs. Discrepancy between methods (either in magnitude and pattern) aroused from the vertical hydraulic conductivity profiles under highly clogged conditions. It is believed this can be attributed to procedural differences between the methods, such as the method of permeameter insertion (twisting versus hammering). Results from both methods suggest that clogging develops along the shortest distance between water input and output. Results also evidence that the design and maintenance of inlet distributors and outlet collectors appear to have a great influence on the pattern of clogging, and hence the asset lifetime of HSSF CWs.

The modification effects of hematite with aluminum hydroxide were investigated on the removal of fluoride ions from water using batch experiments. The effects of pH, contact time, fluoride concentration, and the dose of sorbent on the sorption of fluoride ions by a modified hematite were studied. Characterization of hematite before and after the modification with aluminum hydroxide was studied by X-ray diffraction, scanning electron microscope, and Brunauer–Emmett–Teller. Equilibrium was reached in 48 h of contact time and the maximum sorption of fluoride was found in the pHeq range between 2.34 and 6.26. The Elovich model described the kinetic sorption processes and the Langmuir–Freundlich model, the sorption isotherm process. These results indicated that the sorption mechanism was chemisorption on a heterogeneous material.

Background. The Marilao, Meycauayan and Obando river system (MMORS), in the Philippines is home to many precious metals refineries, where local artisanal gold smelting industries use silver to draw gold out of used jewelry. Copper recovers the silver. The copper-rich wastewater contributes to local pollution. Alternative methods for silver recovery include electrolytic recovery: removal of silver ions from solution, and conversion of the ions into metallic silver. Objectives. Explore operation and scale-up for the electrolytic recovery of silver for small-to-medium-scale used gold smelting plants. Methods. Effects of current and time were investigated in a laboratory scale, magnetically-stirred electrolysis reactor, using a sintered platinum anode and a stainless steel cathode. Silver recovery (the removal of silver ions from solution) was evaluated at different levels of constant operating current, and data was used to determine charge dose as the scale up and operating factor. Charge dose was then used to obtain the operating conditions on a pilot scale (100 L) system. A preliminary pilot test assessed silver recovery performance. Results. Higher silver removal rates were noted at higher operating currents. Electrodeposition at 9 amperes showed 98.7% silver recovery after 30 mins. The charge dose for silver electrodeposition was 1.23 coulombs/mg silver ions removed, while the average electrolysis energy requirement was about 0.59 kilowatt hours/kg of silver removed. Conclusions. Preliminary comparisons on a 100-liter scale, showed the electrolytic process had a higher silver removal (~ 90%) compared to copper displacement (~ 65%). Results are useful for the process design of a complete field test system. Competing Interests. The authors declare no competing financial interests.

Background. The groundwater of Argentina’s Chaco plain presents arsenic levels above those suitable for human consumption. Studies suggest skin disorders among local populations caused by arsenic intake. The relationship between urinary arsenic and arsenic in drinking water is well known, but urinary arsenic alone is not enough for risk assessment due to modulating factors such as the intake of selenium and antimony. Objectives. Determining the relationship between urinary arsenic, selenium and antimony could contribute to the study of arsenic metabolization in humans. Methods. Arsenic, selenium and antimony, relative to urinary creatinine, was quantified in urine samples to assess exposure to arsenic and its toxicity modulators. Results. Arsenic levels were higher than reference value in 89% of exposed group. Selenium concentrations were higher in 84%. Levels of antimony were also surprisingly high, not compatible with dietary intake. Urinary arsenic and selenium data showed highly significant correlations with age. Adult females presented higher urinary arsenic values than adult males. Conclusions. Values related to urinary creatinine were much higher than values considered normal. Concentrations of arsenic and selenium diminished with age for children and increased for adults. Women showed higher concentrations than men. Positive correlation was found between arsenic and selenium. No correlation was seen between urinary antimony, arsenic nor selenium. Competing Interests. The authors declare no competing financial interests.

The aim of this study was to evaluate the use of metal concentrations in clam organs to monitor metal contamination in coastal sediments. The concentrations of Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn were measured in the kidneys, gonads, mantles, gills, digestive gland, and hearts of the infaunal clam Amiantis umbonella collected from a contaminated site near desalination and power plant discharges, and a reference site in Kuwait Bay. Metal concentrations in sediment and sediment pore water were also measured at the collection sites of individual clams at the contaminated site. The concentrations of all metals in all organs (except Zn in the digestive gland) were significantly higher in clams from the contaminated site than from the reference site. Metal concentrations in several organs in A. umbonella from the contaminated site were correlated with those in the sediments and pore waters to which they were exposed. However, fresh weights of gonads, gills, and mantles were significantly lower in clams from the contaminated site compared to the reference site, indicating that the observed elevated concentrations of metals in the organs of clams from the contaminated site largely reflect lower organ weights, rather than higher metal loads, and that these organs in A. umbonella and perhaps other clams are not appropriate for use as biomonitors of metal contamination. Metal concentrations in clam kidneys showed a wide dynamic range with respect to environmental contamination and kidney weight was not variable. Therefore, metal concentrations in clam kidneys provide a reliable biomonitor of contaminant metals in coastal marine sediments.