The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005–2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ∼1month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.

Combinations of sequential anaerobic and aerobic process enhance the treatment of textile wastewater. The aim of this study was to investigate the treatment of diazo dye Reactive Black 5 (RB5)-containing wastewater using granular activated carbon (GAC)–biofilm sequencing batch reactor (SBR) as an integration of aerobic and anaerobic process in a single reactor. The GAC–biofilm SBR system demonstrated higher removal of COD, RB5 and aromatic amines. It was observed that the RB5 removal efficiency improved as the concentration of co-substrate in the influent increased. The alternative aeration introduced into the bioreactor enhanced mineralization of aromatic amines. Degradation of RB5 and co-substrate followed second-order kinetic and the constant (k 2) values for COD and RB5 decreased from 0.002 to 0.001 and 0.004 to 0.001 l/mg h, respectively, as the RB5 concentration increased from 100 to 200 mg/l in the GAC–biofilm SBR system.

Constructed wetlands are recognized as a reliable technology for rural wastewater treatment. However, conventional constructed wetlands face problems with low pollutant removal efficiency and limited oxygen transfer capability. Therefore, a novel vertical flow constructed wetland (VFCW) system with drop aeration was developed in this study. Two pilot-scale vertical flow constructed wetlands of 0.75 m2 each were constructed with the same dimensions and configuration but different media, one of which (named as CW1) was filled with a 1:1 mixture (by weight) of zeolite and dolomite and the other (named as CW2) with the same zeolite only. The oxygen transfer capability of a multilevel two-layer drop aeration device, organics and nitrogen removal of CW1 and CW2, and pollutant distribution along the depths of CW1 and CW2 in different operational phases were studied. The results demonstrated that compared with the direct drop aeration process, the multilevel, two-layer drop aeration device supplied 2–6 mg/L higher dissolved oxygen per meter of drop height, and after installation of the six-level, two-layer drop aeration devices, the 5-day biochemical oxygen demand removal load was improved from 8.1 to 14.2 g m−2 day−1 for CW1. With regard to the different filter media, nitrogen removal was improved by the adsorption of zeolite in the first year, with 5–36% higher NH 4 + –N removal efficiency of CW2 compared with that in CW1. Since it did not have a significant positive effect on phosphate removal, dolomite can be replaced by zeolite. The chemical oxygen demand removal mainly took place in the upper 15-cm filter layer in different operational phases, while nitrogen distribution along the depths of the VFCWs was different in different operational phases. In addition, as no operational problems occurred, the vertical flow constructed wetland system with drop aeration is an appropriate alternative for rural wastewater treatment, with numerous advantages of low capital and operation costs, no energy consumption, easy maintenance, high hydraulic loading rate, high pollutant removal efficiency, and no clogging.

This study compared the tolerance limits of selected bacterial (Bacillus licheniformis, Brevibacillus lactosporus and Pseudomonas putida) and protozoan (Aspidisca, Trachelophyllum and Peranema) species to V5+ in wastewater systems. The isolates were exposed to various concentrations of V5+ (from 10 to 240 ppm), and their tolerance limits to this heavy metal were assessed at different temperatures (25, 30, 35 and 40°C) and pHs (4, 6, 7, 8 and 10) for 5 days. Chemical oxygen demand (COD), dissolved oxygen (DO) and die-off rate of the isolates were measured using standard methods. The results indicated that test isolates were tolerant to V5+, with a gradual decrease in their colony/cell counts when V5+ concentration gradually increased. Bacterial species were found to be more significantly tolerant (MIC: 110–230 ppm V5+) to V5+ than protozoan species which showed an earlier total inhibition/die-off rate (100%) at 60–100 ppm V5+ (MIC) (p < 0.001). P. putida was the most tolerant bacterial species (MIC: 230 ppm V5+) and Aspidisca sp. the most sensitive protozoan species (MIC: 60 ppm V5+). An increase in COD and DO removal was observed throughout the experimental period. The highest COD increase (up to 237.11%) and DO removal (almost 100%) were observed in mixed liquor inoculated with P. putida after exposure to 10 ppm V5+. Changes in pH and temperature affected the tolerance limits of all isolates. This study suggests the use of these tolerant bacterial and protozoan species in the bioremediation of V5+ from domestic and industrial wastewater under the control of pH and temperature.

This paper analyses the influence of activated sludge technologies on the Particle Size Distribution (PSD) of urban wastewater treatment plants operating under real conditions. The activated sludge treatment systems selected for the analysis are the most widely used in wastewater treatment installations: (a) double step activated sludge, (b) medium load activated sludge, (c) prolonged aeration, and (d) membrane bioreactors The main quality parameters (suspended solids, turbidity, and COD) and PSD in the influent and effluent of each different activated sludge treatment were analyzed during 1 year. The PSD was fitted using the power law ([Formula: see text]) obtaining coefficients A and b to define the particle distribution. Mathematical correlations between this coefficients and the rest of parameters studied were found [Formula: see text]. The relation with the average particle size by mass was also found, ([Formula: see text]). Moreover, a relation between PSD and the particle elimination efficiency of the secondary treatment was study, ([Formula: see text]). Finally, the particulate matter nature was assessed by SEM-EDX. It can be concluded that membrane bioreactor is the technology that produces the best water quality effluent due to physic process of particle separation by ultrafiltration membrane technology.

To improve domestic wastewater treatment for total nitrogen (TN) removal, a full-scale constructed wetlands combining an artificially aerated vertical- (AVCW) and a horizontal-flow constructed wetland (HCW) was completed in July 2007. The system covered a total area of 7,610 m². From 2 July 2007 to 7 August 2008, the treatment capacity was 2,076 m³ day⁻¹ with an aeration quantity of 7,400 m³ day⁻¹. The system effectively reduced the average annual output of BOD₅ (52.0 %), NH₄–N (58.41 %), and TP (41.61 %), although the percentage reductions of other pollutants, including chemical oxygen demand (34.1 %), suspended solid (38.9 %), and TN (31.05 %) were lower. The purpose of the HCW was for denitrification of the effluent from the AVCW, and annual average of 34.27 % of NO₃–N was removed compared with the reading at the AVCW outlet. With hydraulic loading increased to 4,152 m³ day⁻¹ from 9 September to 23 November 2007, the removal rate for NO₃–N from the HCW decreased substantially from 48.80 to 18.86 %. The total removal rates of NH₄–N showed significant positive correlation with DO content in the AVCW and with total TN removal rates for the combined system (P < 0.05). The study indicated that, even with limited artificial aeration, nitrification was very effective for NH₄–N removal.

Chestnut agro-industrial companies consume a high volume of water for washing and processing fruit, generating a large volume of wastewater. This work studied the biodegradation of chestnut processing wastewater through aerobic assays, varying substrate, and biomass concentrations. In general, this wastewater presents a good biodegradability, especially in experiments with relatively low chemical oxygen demand (COD) (0.4 and 0.6 g O₂ L⁻¹) allowing a COD removal of 85–90 %. The best results were obtained in the reactor initially loaded with 2 g L⁻¹ of biomass and 0.4 or 0.6 g O₂ L⁻¹ of COD. These experiments also showed high COD removal rates: 4.25 and 3.88 g COD g⁻¹ volatile suspended solids (VSS) h⁻¹, respectively. The sedimentation rate, evaluated for different initial values of biomass (1, 2, and 3 g L⁻¹), always presented higher values in the experiments with 2 and 3 g L⁻¹ of biomass, regardless of the initial COD value used. After comparing different kinetic models (Monod, Contois, and Haldane), it was observed that the Haldane inhibition model satisfactorily describes the COD biodegradation. AQUASIM software allowed calculating the kinetic constant ranges: K ₛ, 1.59–6.99 g COD L⁻¹; ν ₘₐₓ, 25–40 g COD g⁻¹ VSS day⁻¹; and K ᵢ values, 0.07–0.11. These kinetic constants corresponds to maximum rates (ν*) between 1.48 and 4.25 g COD g⁻¹ VSS day⁻¹ for substrate concentrations (S*) from 0.38 to 0.88 g COD L⁻¹.

The aim of this work was to evaluate the role of three biopolymers used as coagulant–flocculant aids in the treatment of a high-load cosmetic industry wastewater (WW) located in Mexico. Discussion is based on a surface response methodology. When using guar, locust bean gum, and Opuntia mucilage, conductivity and turbidity removals as high as 20.1 and 67.8 % were found, respectively. Chemical oxygen demand (COD) removals as high as 38.6 % were observed. The maximum removal efficiency was found for mucilage, with 21.1 mg COD/mg polymer. At the end of the process, pH was in the range of 5.8–7.3 for an initial wastewater pH value of 5.6. The production of sludge was very dependent on the WW organic load. An analysis of some metal content in the sludges is presented. From the response surface analysis, it was observed that the parameter which strongly affected the removal of COD, turbidity, oil and greases (O&G), and the amount of sludge including their metal contents was the polymer dose. Only in the case of O&G removal was a combination of dose–wastewater organic load responsible for the removals. The values of R ² for the correlation process were between 0.5451 (O&G) and 0.7989 (COD). The p values for the different expressions were between 0.1985 (COD) and 0.7195 (O&G). The values of adequate precisior (AP) indicate how feasible it is to use the surface response analysis (AP > 4). Most of the analysis indicated that AP > 4, except in the case of the O&G removal analysis where AP = 2.9.

Aircraft and pavement deicing formulations and other potential freezing point depressants were tested for biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Propylene glycol-based aircraft deicers exhibited greater BOD5 than ethylene glycol-based aircraft deicers, and ethylene glycol-based products had lower degradation rates than propylene glycol-based products. Sodium formate pavement deicers had lower COD than acetate-based pavement deicers. The BOD and COD results for acetate-based pavement deicers (PDMs) were consistently lower than those for aircraft deicers, but degradation rates were greater in the acetate-based PDM than in aircraft deicers. In a 40-day testing of aircraft and pavement deicers, BOD results at 20°C (standard) were consistently greater than the results from 5°C (low) tests. The degree of difference between standard and low temperature BOD results varied among tested products. Freshwater BOD test results were not substantially different from marine water tests at 20°C, but glycols degraded slower in marine water than in fresh water for low temperature tests. Acetate-based products had greater percentage degradation than glycols at both temperatures. An additive component of the sodium formate pavement deicer exhibited toxicity to the microorganisms, so BOD testing did not work properly for this formulation. BOD testing of alternative freezing point depressants worked well for some, there was little response for some, and for others there was a lag in response while microorganisms acclimated to the freezing point depressant as a food source. Where the traditional BOD5 test performed adequately, values ranged from 251 to 1,580 g/kg. Where the modified test performed adequately, values of BOD28 ranged from 242 to 1,540 g/kg.

The presence of synthetic dyes in industrial wastewaters may create serious environmental problems due to their mutagenicity and toxicity to aquatic life and humans. In this study, the decolourization and degradation of methylene blue (MB) by a Sphingomonas paucimobilis strain isolated from industrial wastewater was investigated under aerobic conditions. Decolourization extent of MB in medium was over 85 % when the bacterium was grown on a high concentration of the dye (1,000 mg/L) after a retention time of 5 days, while reduction in COD was 92.99 % suggesting mineralization of dyes as a result of microbial activities. The bacterium retained decolourizing activity over a wide range of pH (2–10), with peak activity obtained at pH 9. Analysis of samples extracted from decolourized culture flasks at pH 9 using UV–visible and Fourier transform infrared (FTIR) spectroscopy confirmed that the mechanism of colour removal was due to biodegradation rather than adsorption of dye on cells. Scanning and transmission electron microscopy revealed the secretion of exopolysaccharides (EPS) by S. paucimobilis cells on exposure to MB—a probable physiological defence mechanism to ensure controlled diffusion of dye molecules into cellular structures. Biokinetic coefficients, namely, growth yield, Y; specific biomass decay, K d; maximum specific substrate rate, k; saturation constant for substrate, K ₛ; and maximum specific biomass growth rate, μ ₘₐₓ, were determined by the Monod type kinetic equation. Results indicate that S. paucimobilis holds a promise as a good candidate for the biological treatment of industrial effluent containing high concentrations of synthetic dyes.