The biomass characteristics, the process performance, and the microbial community for a sequencing batch reactor (SBR) and a submerged membrane SBR (MSBR) were evaluated. A synthetic wastewater containing only 4-chlorophenol (4CP) was used as the sole source of carbon and energy. Degradation efficiencies of 4CP were higher than 99% for both reactors, and no significant differences on the 4CP degradation rates were observed for the SBR (116.9 ± 0.9 mg 4CP g VSS−1 h−1) as well as for the MSBR (117.3 ± 0.5 mg 4CP g VSS−1 h−1). Despite the similar results obtained for the physicochemical parameters, it was found that the biomass characteristics were different considering the sludge volumetric index, settling velocity, protein content in the mixer liquor, and total suspended solids in the effluent. The settling velocity was three times higher in the SBR than in the MSBR; however, a better quality, considering suspended solids, was observed for the MSBR. The protein concentration in the mixed liquor was higher in the MSBR than in the SBR, generating foaming problems in the MSBR. A similarity analysis was made with the Ochiai–Barkman index. Even though the reactors were inoculated with the same biomass, significant differences in the composition and populations dynamics were observed.

Vicinities of manufactured gas plants were often contaminated with solid iron–cyanide complexes as a result of the coal gasification process. During the remediation of affected soils, knowledge about contaminant concentrations is crucial, but laboratory methods are often expensive and time consuming. Rapid and non-destructive field methods for contaminant determination permit an analysis of large sample numbers and hence, facilitate identification of ‘hot spots’ of contamination. Diffuse near infrared reflectance spectroscopy has proven to be a reliable analytical tool in soil investigation. In order to determine the feasibility of a Polychromix Handheld Field Portable Near-Infrared Analyzer (FP NIR), various sample preparation methods were examined, including homogenizing, sieving, drying, and grinding. Partial least squares calibration models were developed to determine near infrared (NIR) spectral responses to the cyanide concentration in the soil samples. As a control, the contaminant concentration was determined using conventional flow injection analysis. The experiments revealed that portable near-infrared spectrometers could be a reliable device for detecting cyanide concentrations >2,400 mg kg⁻¹ in the field and >1,750 mg kg⁻¹ after sample preparation in the laboratory. We found that portable NIR spectrometry cannot replace traditional laboratory analyses due to high limits of detection, but that it could be used for identification of contamination ‘hot spots’.

An excess of phosphorus (P) is the most common cause of eutrophication of freshwater bodies. Thus, it is imperative to reduce the concentration of P to prevent harmful algal blooms. Moreover, recovery of P has been gaining importance because its natural source will be exhausted in the near future. Therefore, the present work investigated the removal and recovery of phosphate from water using a newly developed hybrid nanocomposite containing aluminium nanoparticles (HPN). The HPN-Pr removes 0.80 ± 0.01 mg P/g in a pH interval between 2.0 and 6.5. The adsorption mechanism was described by a Freundlich adsorption model. The material presented good selectivity for phosphate and can be regenerated using an HCl dilute solution. The factors that contribute most to the attractiveness of HPN-Pr as a phosphate sorbent are its moderate removal capacity, feasible production at industrial scale, reuse after regeneration and recovery of phosphate.

The photocatalytic degradation of dyes under sunlight irradiation has received much attention not only because the attempt is aimed at decomposition of pollutants but also at finding methods of making use of solar energy. Following this line, zinc oxide nano-particles were prepared using solvent thermal method in order to decompose Naphthol Green B in presence of sunlight. Complete mineralization and decolorization of Naphthol Green B were achieved in 14 h. In order to reduce the band gap of zinc oxide and increase its photocatalytic activity in sunlight, it was doped with different concentrations of aluminum (1 %, 3 %, 5 %, and 10 %). The obtained band gap energy of the Al-doped ZnO nanoparticles was investigated as a function of Al content. Reduction of band gap energy for the heavily doped ZnO nanoparticles (10 % Al) was observed from 3.29 to 3.23 eV leading to fast transfer for electron from the excited state of dye to conduction band of ZnO. Therefore, by using the 10 % Al-doped ZnO nanoparticles, the complete mineralization and decolorization of Naphthol Green B were achieved in 6 h under sunlight. These results suggested that the heavily doped ZnO nanoparticles with aluminum has a positive effect towards photocatalytic reactions with dye under solar energy.

Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus (P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg−1 mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L−1) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels. A rate of 30 g ochre kg−1 soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L−1, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other amendments.

Odors, such as the malodorous and toxic hydrogen sulfide (H₂S), are released during leachate collection, storage, and treatment. A full-scale biofilter was applied to treat H₂S emitted from a leachate equalization basin in a sanitary landfill site. The inlet concentration of H₂S was 26.3–213.0 mg m⁻³. In steady state, total removal efficiency was over 90 % in summer and over 80 % in winter. The maximum elimination capacity achieved 9.1 g m⁻³ h⁻¹ at a loading rate of 10.5 g m⁻³ h⁻¹. The biofilter was effective at reducing H₂S. Factors on the level of H₂S inlet concentration and performance of the biofilter were investigated. The H₂S inlet load and removal efficiency relied on ambient and biofilter temperature, respectively. The water containing rate and relative humidity presented seasonal variation, according to which the interval period of irrigation could be optimized. The main product of H₂S degradation was sulfate, and sulfur also could be observed from the biofilter. Spatial and temporal shifts in bacterial community composition in the biofilter were determined by polymerase chain reaction-denaturing gradient gel electrophoresis followed by DNA sequence analysis. The present study revealed a correlation between biofilter performance and bacterial community structure, especially in a real application case.

Electrochemical processes in industrial effluents have been studied as a means to obtain higher efficiency in wastewater treatment. Heterogeneous photocatalysis appears as a low-cost alternative through the use of lower wattage lamps and thermal TiO₂ films. Photocatalysis became a clean process for water treatment due to hydroxyl radicals generated on semiconductor surface. Such radicals are able to degrade several organic compounds. This study used different electrodes and analytical methods for degradation of phenol molecules to reduce treatment costs, improve efficiency, and identify compounds formed during the decomposition of phenolic molecules. Thermal growth of TiO₂ film was observed on the titanium electrode in rutile form. Application of an electrical potential on the Ti/TiO₂ working electrode increases efficiency in reducing concentration of phenol after photocatalytic treatment. Still, high energy radiation (UVC) showed best degradation rates in photolytic process. Different compounds formed during the degradation of phenol were also identified in the UVC–PE treatment.

The present work discusses the startup and operation of different biotrickling filters during the simultaneous removal of NH3, H2S, and ethyl mercaptan (EM) for odor control, focusing on (a) the impact of pH control in the stability of the nitrification processes during reactor startup and (b) the crossed effects among selected pollutants and their by-products. Two biotrickling filters were packed with poplar wood chips (R1 and R2A), while a third reactor was packed with polyurethane foam (R2B). R2A and R2B presented a pH control system, whereas R1 did not. Loads of 2–10 g N–NH3 m−3 h−1, 5–16 g S–H2S m−3 h−1, and 1–6 g EM m−3 h−1 were supplied to the bioreactors. The presence of a pH control loop in R2A and R2B proved to be crucial to avoid long startup periods and bioreactors malfunctioning due to biological activity inhibition. In addition, the impact of the presence of different concentrations of a series of N species (NH 4 + , NO 2 − , and NO 3 − ) and S species (SO 4 2− and S2−) on the performance of the two biotrickling filters was studied by increasing their load to the reactors. Sulfide oxidation proved to be the most resilient process, since it was not affected in any of the experiments, while nitrification and EM removal were severely affected. In particular, the latter was affected by SO 4 2− and NO 2 − , while nitrification was significantly affected by NH 4 + . The biotrickling filter packed with polyurethane foam was more sensitive to crossed effects than the biotrickling filter packed with poplar wood chips.

Over the last decades, removal of potentially toxic and hazardous materials has received a great deal of attention in the field of environmental pollution. Problems associated with the disposal of the wastes of different kinds of industries led to studies of the sorption–uptake properties of clay minerals and zeolites. In the present research, the behavior of vermiculite particles ranging between 425 and 500 μm in a laboratory-scale fluidized bed column for uptake of Cs, Hg, and Mn ions from aqueous solutions and wastes in the presence of competing cations has been studied in order to investigate techniques for decontamination of liquid phases. Vermiculite selectively removed high percentages of Cs even from low concentrations in the presence of competing cations. Also removed were up to 60 % of added Hg²⁺ at concentrations of 5 ppm from drinking water and about 84 % from seawater, and furthermore, Mn²⁺ was selectively removed from low-concentration (ca 10 ppm) industrial wastes even when the ratio of Mn²⁺ to competing cations was 1:94. The results suggest the potential use of vermiculite as decontaminating agent in well-designed fluidized bed columns.

In this work, the electrochemical treatment of an effluent from the pharmaceutical industry with boron-doped diamond electrodes was investigated. The electrolyses were carried out in a discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single-compartment electrochemical flow cell. The effect of operating conditions, such as current density (from 25.7 to 179.4 mA cm2) and flow rate (from 104.8 to 564.7 cm3 min−1), at residence times between 0 and 570 min, was studied. Design of experiments was used for optimizing the process. The global contribution of operative parameters and evolution of the residence time in TOC removal was studied, and a time of 77 min was obtained in order to evaluate the highest influence of the operative parameters. For this time, ANOVA test reported significance for four of the five involved variables. The current density was found to have a considerable positive effect on TOC removal, whereas the flow rate was found to have a moderate negative effect on target variable.