A coagulation treatment study was conducted using both natural (sago and potato flour) and commercial (poly aluminum chloride and aluminum sulfate) coagulants in semiconductor wastewater. The effects for settling time and dosage of the coagulants as well as their interactions on the reduction of chemical oxygen demand (COD) and turbidity were investigated using a three level factorial design, Response Surface Methodology (RSM). Sago concentration showed more influence on the COD and turbidity reduction than settling time, with concentrations lower than 1.5 g L⁻¹ giving the better reduction. The interaction of settling time and concentration on the COD and turbidity were observed when using potato starch. Concentrations higher than 1.5 g L⁻¹ potato starch reduced the COD and turbidity better. The polyaluminium chloride and ammonium sulphate revealed that lower concentrations (0.02-1.0 g L⁻¹) and longer settling time (30-60 min) gave the greatest reduction in COD and turbidity.

Regional air pollution in northeast Asia is an emerging environmental problem requiring long-term impact assessment of acidic deposition. In this study, the gridded distribution of nitrogen uptake led by both growing forests and harvested biomass for eight tree species: Japanese Larch, Red pine, Korean pine, Oak tree, Chestnut, Other Conifers, Other broad leaved trees, and Mixed forest was identified to estimate critical loads for nitrogen over South Korea. The gridded spatial distribution of averaged nitrogen uptake was mapped by 0.125° Latitude x 0.125° Longitude resolution. The results showed that net uptake of nitrogen led by both growth and harvested biomass was totaled at 438 molc ha-¹ year-¹ among which harvested biomass contribution was estimated to be 25 molc ha-¹ year-¹, yielding a very small fraction of total nitrogen uptake presumably due to the younger stages of forest in South Korea.

Mercury and organic carbon concentrations vary dynamically in streamwater at the Sleepers River Research Watershed in Vermont, USA. Total mercury (THg) concentrations ranged from 0.53 to 93.8 ng/L during a 3-year period of study. The highest mercury (Hg) concentrations occurred slightly before peak flows and were associated with the highest organic carbon (OC) concentrations. Dissolved Hg (DHg) was the dominant form in the upland catchments; particulate Hg (PHg) dominated in the lowland catchments. The concentration of hydrophobic acid (HPOA), the major component of dissolved organic carbon (DOC), explained 41-98% of the variability of DHg concentration while DOC flux explained 68-85% of the variability in DHg flux, indicating both quality and quantity of the DOC substantially influenced the transport and fate of DHg. Particulate organic carbon (POC) concentrations explained 50% of the PHg variability, indicating that POC is an important transport mechanism for PHg. Despite available sources of DHg and wetlands in the upland catchments, dissolved methylmercury (DmeHg) concentrations in streamwaters were below detection limit (0.04 ng/L). PHg and particulate methylmercury (PmeHg) had a strong positive correlation (r ² = 0.84, p < 0.0001), suggesting a common source; likely in-stream or near-stream POC eroded or re-suspended during spring snowmelt and summer storms. Ratios of PmeHg to THg were low and fairly constant despite an apparent higher methylmercury (meHg) production potential in the summer. Methylmercury production in soils and stream sediments was below detection during snowmelt in April and highest in stream sediments (compared to forest and wetland soils) sampled in July. Using the watershed approach, the correlation of the percent of wetland cover to TmeHg concentrations in streamwater indicates that poorly drained wetland soils are a source of meHg and the relatively high concentrations found in stream surface sediments in July indicate these zones are a meHg sink.

The selective recovery of Cd from simulated spent nickel–cadmium battery solutions was achieved using a Cd working electrode in a laboratory cell with a three-electrode arrangement in hydrochloric, nitric, and sulfuric acids. The latter was selected for further study of the recovery step. Nitrate media were found to be unsuitable for Cd recovery since nitrates are reduced at the required deposition potentials. Cd(II) deposition on Cd electrodes is favored in sulfate or chloride media since it occurs at a potential some 200 mV less negative than that of Ni(II). A good percent Cd recovery (>90%) with high selectivity (approximately 0% Ni) and a reasonably high current efficiency (>80%) can be achieved under appropriate conditions. The irreversible nature of Ni(II) reduction provides the necessary framework to achieve such a selective separation.

The principles of limestone drain systems that are commonly used to passively remediate acid rock drainage have been adapted and modified for remediation of acidic and metal-rich drainage that is produced from broad scale agricultural land use of regions underlain by Acid Sulfate Soils (ASS). The acidic drainage water from sugar cane fields in an ASS catchment was collected from an open drain, filtered to reduce the transport of large particulates, and passed vertically through a polyethylene tank, which was filled with limestone aggregates (<75 mm). This Closed Tank Reactor (CTR) uses the principles of oxic and anoxic limestone drain systems that are designed to increase the partial pressure of carbon dioxide and thereby the alkalinity produced from the dissolution of limestone by metal-laden influent. During a non-continuous 70 day monitoring period, the discharge from the CTR had higher pH, lower acidity and lower metal concentrations compared to the inflow. Under average flow conditions (9 lpm), similar proportions of incoming dissolved aluminium and iron (61% and 56% respectively) were retained within the CTR. Two perforated pipes in the base of the CTR were used to flush precipitates from the system under rapid flow conditions (>50 lpm). The flushing was effective in removing approximately 10% of accumulated iron but only about 0.3% of accumulated aluminium from the CTR. Accumulation of aluminium inside the CTR is likely to present operational problems in attempts to apply such technology to many coastal acid sulfate soil drains.

The selectivity and uptake capacity of horticultural peat available in Romania was evaluated with respect to the removal of Cd(II), Cr(VI) and Pb(II) ions from aqueous solution. The kinetics, sorption capacities, selectivity and pH dependence of sorption were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir and Freundlich isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solutions containing 300 mg/l of metal, the observed uptake capacities were 20 mg Cd(II)/g peat, 15 mg Cr(VI)/g peat and 30 mg Pb(II)/g peat. The study proved that horticultural peat is a suitable material for the removal of the studied heavy metal ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II), Cr(VI) and Pb(II) ions.

Developing procedures for assessing the potential environmental fate and transport of nanomaterials is an active endeavor of the environmental technical research community. Insufficient information exists for estimating the likelihood of nanomaterial deposition on natural surfaces in aquatic environments. This work develops a framework for estimating potential metal oxide nanomaterial self-aggregation through the combined application of recent developments in diffuse layer model surface complexation theory with historical Derjaguin–Landau–Verwey–Overbeek (DLVO) procedures. Findings from the work include: 1) the surface, diffuse layer, and/or zeta potentials of nanomaterials in environmental aqueous systems are likely to have an absolute value less than 25 mV, 2) only nanomaterials with a Hamaker constant as large as 1E-19 J (and an absolute surface potential < 25 mV) will likely aggregate in most environmental aquatic media, 3) natural organic matter coatings may render metal oxide nanomaterials less likely to aggregate in aquatic systems, 4) nanomaterials in aqueous suspension will likely have an absolute surface potential less than their micron-sized counterparts of the same composition, and 5) robust diffuse layer model databases of intrinsic surface site reactivity constants with multivalent aqueous environmental ions will need to be developed in order to provide accurate mechanistic estimates of the surface potential of nanoparticles suspended in aqueous environmental systems.

The sorption behavior of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, on marine sediments was systematically investigated. The experimental results showed that 100 min was required for the adsorption equilibrium. For the sediments treated by HCl and H₂O, sorption behavior of SDBS was fit with linear isotherm very well over the concentration range studied at 298 K. The sorption occurred primarily due to partition function of hydrophobic chains into organic carbon of sediments. Sorption of SDBS on H₂O₂-treated sediments was satisfactorily fit with Freundlich isotherm model and mainly through surface function of clay minerals in the sediment. The sorption was favorably influenced by the increased salinity, deceased pH and decreased temperature of seawater.

Aqueous phase adsorption of three textile dyes onto a granular activated carbon produced from acid activation of almond shells is presented. Primarily, the sorption of three basic dyes, methylene blue, rhodamine b, and malachite green oxalate were studied. Four models, the Freundlich, the Langmuir, the Redlich-Peterson, and the Toth isotherms were compared for their quality of fit to the single-solute sorption data. Next, sorption of the three likely binary systems was examined. Four bi-solute models, the extended Langmuir with and without an interaction term, the extended Redlich-Peterson with an interaction term, and the empirical extended Freundlich model were used to predict sorption in the binary systems. Nonlinearly determined constants of the corresponding single-solute isotherms were used in the binary models to compare with experimental binary sorption data. For the single-solute system, the three-parameter models of the Redlich-Peterson and the Toth isotherms outperformed the Langmuir and Freundlich models. The empirical extended Freundlich model produced the closest comparison to the binary data in each system. In general, the nonlinear method provided a simple and computationally effective technique of producing optimal fitting parameters for the bi-solute sorption models.

We investigated the coupling of abundance of bacteria, phytoplankton and ciliates with hydrocarbons in the surface water and sediments of five interconnected ponds in the arid Sfax solar salterns. This study aimed at determining the potential sources of hydrocarbons and the effects of salinity gradients on microorganism metabolism. Hydrocarbon analysis was performed by gas chromatography (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). The GC-FID allowed the detection of aliphatic hydrocarbons and n-alkanes ranging from n-C₁₃ to n-C₃₀. Total aliphatic hydrocarbon concentrations varied from 92.5 mg. l-¹ in the first pond (having marine characteristics) to 661.1 mg. l-¹ in the last pond (crystallizer) (316.8 ± 120.1 mg. l-¹) for water samples and from 26.7 to 127.8 μg. g-¹ dry weight for sediment samples. The GC-MS enabled us to detect halogenated hydrocarbons (bromoalkanes and chloroalkanes) and n-alkenes. The distribution of n-alkanes indices coupled to several environmental factors suggests that a major fraction of hydrocarbons resulted from both prokaryotic (bacteria) and eukaryotic (protists) developments. A low hydrocarbon fraction might be petrogenic.