Underwater treatment of lead-contaminated sediment

The sediment associated with the reconstruction of a bridge pier was classifiable as hazardous by the Toxicity Characteristic Leaching Procedure (TCLP), due to elevated concentrations of lead. However, RCRA regulations do not classify the sediment as hazardous unless it is moved. RMT designed an in-situ, underwater treatment process to render the sediment nonhazardous, using phosphate-based chemistry before dredging. Subsequent sediment management was conducted without the additional regulatory requirements and costs associated with managing hazardous waste.     

COMPARING SOME METHODS OF ESTIMATING MEAN AREAL RAINFALL1

ABSTRACT: A comparison of 13 different methods of estimating mean areal rainfall was made on two areas in New Mexico, U.S.A., and one area in Great Britain. Daily, monthly and yearly rainfall data were utilized. All methods, in general, yielded comparable estimates, especially for yearly values. This suggested that a simpler method would be preferable for estimating mean areal rainfall in these areas.     

Application of Sample Selection Model in Estimating Response Functions for Nitrate Percolation

The Seymour aquifer region of Texas has been identified as containing elevated levels of nitrate in ground water. Various state and federal agencies are currently studying policy options for the region by gathering more site-specific information. However, because of lack of sufficient information, cause and effect relationships between water quality and agricultural practices have not been well established for the region. Some recently available biophysical simulation models have impressive capabilities in generating large amounts of data on environmental pollution resulting from agricultural production practices. In this study, the data generated by a biophysical simulation model were used to estimate the nitrate percolation response functions for the Seymour aquifer region. Interestingly, nitrate percolation values obtained from simulation models often comprise acensoredsample because the non-zero percolation values are only observed under certain climatic events and input levels. It has been shown in the econometric literature that the use of Ordinary Least Squares (OLS) on censored sample data produces biased and inconsistent parameter estimates. Thus, a sample selection model was used in this study to estimate the response functions for nitrate percolation. The study provides some insight into the relationship between nitrate percolation and agricultural production practices. In particular, the study demonstrates the potential of selected design standards in minimizing agricultural nonpoint-source (NPS) pollution for the study area.     

Using adsorption and sulphide precipitation as the principal removal mechanisms of arsenic from a constructed wetland – a critical review

This review has been undertaken to understand the role of various parameters such as redox potential, microbes, and organic matters on the fate and transport of arsenic in the constructed wetland. A conceptual diagram of arsenic fate and transport in the constructed wetland was developed. Role of various minerals which are produced due to microbial activities are described. The role of these minerals on arsenic adsorption is discussed. It was envisaged that iron sulphide would be the main adsorbent for arsenic in microbe-mediated adsorption process. Beside microbe-mediated arsenic adsorption, roles of various microbes, such as sulphate reducers and methane producers, on arsenic transformation are discussed. Role of various organic carbon sources and electron acceptors on the proliferation of the above mentioned microbes with respect to arsenic transformation was envisaged. Role of dissolved organic matters on arsenic transformation and transport was also discussed in details. To strengthen the review, laboratory studies and modelling of arsenic adsorption and transformation using the Visual Minteq were appended.     

Bioremediation potential of Brevibacillus parabrevis AMB-CD-2 in spinach under lead toxicity

The present study was conducted to evaluate the impact of lead toxicity on the growth parameters of spinach and the performance of lead-resistant bacterial isolates under lead stress conditions. Out of four bacterial isolates selected for this study, only two isolates AMB-CD-2 and AMB-CD-4 were selected based on their lead tolerance ability. A polybag experiment was conducted with six treatments and four replications in spinach. The treatments included T₁ (RDF + control), T₂ (lead acetate), T₃ (AMB-CD-2 + lead), T₄ (AMB-CD-4 + lead), T₅ (AMB-CD-2), and T₆ (AMB-CD-4). Results showed that lead contamination significantly decreased plant growth parameters, particularly in the treatment T₂ (lead acetate) when compared with other treatments. Similarly, reduced uptake of nitrogen, phosphorus, and potassium (NPK) was recorded in T₂. Inoculation with lead-resistant bacteria, AMB-CD-2, significantly improved plant growth parameters (plant height, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, and root length). The uptake of NPK was higher in T₅ (AMB-CD-2) in the absence of lead by approximately 0.81%, 0.37%, and 0.42% than in the control, respectively. Through atomic absorption spectrophotometer analysis, the lead concentration in treatment T₂ (control) was about 3.20 mg/g while in treatment T₃ (AMB-CD-2 + lead) it was about 1.32 ppm. The 16S rRNA gene sequencing revealed that AMB-CD-2 resembles Brevibacillus parabrevis. The results demonstrate that the lead-resistant bacteria B. parabrevis AMB-CD-2 showed a significant lead reduction of approximately 58.75% compared to the control.     

Load maximization of a liquid-solid circulating fluidized bed bioreactor for nitrogen removal from synthetic municipal wastewater

A novel liquid-solid circulating fluidized bed bioreactor (LSCFB) configured with anoxic and aerobic columns and lava rock as the biofilm carrier was used to treat synthetic municipal wastewater. Four different empty bed contact times (EBCTs) of 0.82, 0.65, 0.55, and 0.44 h were examined to optimize nutrient removal capability of the system. The LSCFB demonstrated tertiary effluent quality organic and nitrogen removal efficiencies. Effluent characteristics of the LSCFB were soluble biological oxygen demand (SBOD)10 mg l(-1) and total nitrogen (TN)<10 mg l(-1) at organic loading rate (OLR) of 5.3 kg m(-3)d(-1) and nitrogen loading rate of 0.54 kg Nm(-3)d(-1). Remarkably low yields of 0.14, 0.17, 0.19, and 0.21 g VSS g(-1)COD were observed at OLR of 2.6, 3.2, 4.1 and 5.3 kg COD m(-3)d(-1), where increment of biomass growth and detachment rate were also experienced with increasing OLR. However the system demonstrated only 30% phosphorus removal, and mass balances along the anoxic and aerobic columns showed biological phosphorus removal in the system. Organic mass balance showed that approximately 40% of the influent COD was utilized in the anoxic column and the remaining COD was oxidized in the aerobic column. The system is very efficient in nitrification-denitrification, with more than 90% nitrification of ammonium and overall nitrogen removal in the LSCFB was 70+/-11% even at an EBCT of 0.44 h.     

Comparative studies on biomass productivity and lipid content of a novel blue-green algae during autotrophic and heterotrophic growth

Environmental Science and Pollution Research - Algae have long been acclaimed as the attractive renewable source for generating third-generation biofuels, particularly biodiesel. Under the present...     

Stagnant surface water bodies (SSWBs) as an alternative water resource for the Chittagong metropolitan area of Bangladesh: physicochemical characterization in terms of water quality indices

The concern over ensuing freshwater scarcity has forced the developing countries to delve for alternative water resources. In this study, we examined the potential of stagnant surface water bodies (SSWBs) as alternative freshwater resources in the densely populated Chittagong metropolitan area (CMPA) of Bangladesh??where there is an acute shortage of urban freshwater supply. Water samples were collected at 1-month intervals for a period of 1 year from 12 stations distributed over the whole metropolis. Samples were analyzed for pH, water temperature (WTemp), turbidity, electrical conductivity (EC), total dissolved solids, total solids, total hardness, dissolved oxygen (DO), chloride, orthophosphates, ammonia, total coliforms (TC), and trace metal (Cd, Cr, Cu, Pb, As, and Fe) concentrations. Based on these parameters, different types of water quality indices (WQIs) were deduced. WQIs showed most of CMPA-SSWBs as good or medium quality water bodies, while none were categorized as bad. Moreover, it was observed that the minimal water quality index (WQI_m), computed using five parameters: WTemp, pH, DO, EC, and turbidity, gave a reliable estimate of water quality. The WQI_m gave similar results in 72% of the cases compared with other WQIs that were based on larger set of parameters. Based on our finding, we suggest the wider use WQI_m in developing countries for assessing health of SSWBs, as it will minimize the analytical cost to overcome the budget constraints involved in this kind of evaluations. It was observed that except turbidity and TC content, all other quality parameters fluctuated within the limit of the World Health Organization suggested standards for drinking water. From our findings, we concluded that if the turbidity and TC content of water from SSWBs in CMPA are taken care of, they will become good candidates as alternative water resources all round the year.     

Balance of conversion and degradation of 2,6-dichlorobenzonitrile -14C in humus soil

In a closed aerated laboratory soil test, volatilization and mineralization of 2,6-dichlorobenzonitrile-¹⁴C is negligible within 61 days. The major soil residues are parent compound, 2,6-dichlorobenzamide and unextractable residues.