The present study aims to optimize the slow release biostimulant ball (BSB) for bioremediation of contaminated coastal sediment using response surface methodology (RSM). Different bacterial communities were evaluated using a pyrosequencing-based approach in contaminated coastal sediments. The effects of BSB size (1–5cm), distance (1–10cm) and time (1–4months) on changes in chemical oxygen demand (COD) and volatile solid (VS) reduction were determined. Maximum reductions of COD and VS, 89.7% and 78.8%, respectively, were observed at a 3cm ball size, 5.5cm distance and 4months; these values are the optimum conditions for effective treatment of contaminated coastal sediment. Most of the variance in COD and VS (0.9291 and 0.9369, respectively) was explained in our chosen models. BSB is a promising method for COD and VS reduction and enhancement of SRB diversity.

Two sediment cores were obtained from Kasado Bay, a moderate-polluted enclosed bay in Japan, to examine anthropogenic impacts on Ostracoda over the past ca. 70years. We analyzed ostracode abundance and diversity, grain size, and CHN, and used 210Pb and 137Cs as the dating method. The present study showed that cross-plot comparisons of ostracode abundance and each environmental factor, based on sediment core data, could be used to identify ostracode species as indicators for anthropogenic influences. Ostracode abundance reflected mainly the changes that had occurred in total organic carbon content in sediments related to eutrophication, but heavy metal concentration did not directly influence several ostracode abundance in the bay. Environmental deterioration because of eutrophication started in the 1960s. The regulations regarding the chemical oxygen demand in waters introduced in the 1980s probably influence ostracode abundance for certain species in this period. Currently, Kasado Bay is not experiencing severe degradation.

In this study, the occurrence and spatial distribution of 38 antibiotics in surface water and sediment samples of the Hailing Bay region, South China Sea, were investigated. Twenty-one, 16 and 15 of 38 antibiotics were detected with the concentrations ranging from <0.08 (clarithromycin) to 15,163ng/L (oxytetracycline), 2.12 (methacycline) to 1318ng/L (erythromycin–H2O), <1.95 (ciprofloxacin) to 184ng/g (chlortetracycline) in the seawater, discharged effluent and sediment samples, respectively. The concentrations of antibiotics in the water phase were correlated positively with chemical oxygen demand and nitrate. The source analysis indicated that untreated domestic sewage was the primary source of antibiotics in the study region. Fluoroquinolones showed strong sorption capacity onto sediments due to their high pseudo-partitioning coefficients. Risk assessment indicated that oxytetracycline, norfloxacin and erythromycin–H2O posed high risks to aquatic organisms.

Natural (AC-N) and electrochemical iron-modified activated carbon (AC-Fe-2.5A) were applied to treat wastewater with organic by-products generated by the manufacture of acrylic resins from methyl methacrylate (MMA) using batch and column systems. MMA wastewater has an extremely complex composition with a chemical oxygen demand concentration of 651.25 g O₂/L, total organic carbon (TOC) concentration of 227.86 g/L, NH₄⁺concentration of 62.74 g/L, and 352,500 PtCo units. Wastewater was distilled to decrease the ammonium concentration with a removal efficiency of ammonium of 52 %. Then, Fenton oxidation was applied in order to promote the partial oxidation of organic matter; the molar dosage of Fe²⁺/H₂O₂was 0.018/5.700 at pH 5.3. After distillation and oxidation processes, batch experiments using natural and iron-modified activated carbon were carried out in order to determinate the adsorption equilibrium time and capacities. The global removal percentages of TOC by oxidation–adsorption treatment were the highest at pH 2, 21.09 and 29.46 % for AC-N and AC-Fe-2.5A, respectively, and for color were most efficient at pH 4, 80.62 and 72.55 % for AC-N and AC-Fe-2.5A, respectively. The results showed that AC-Fe-2.5A was more efficient than AC-N for the removal of TOC. The electrochemical modification improves the adsorption capacities and properties of activated carbon.

The anaerobic biodegradability of combined microwave-ultrasonic pretreated thickened excess activated sludge (PTEAS) mixed with raw primary sludge (PS) was investigated in this study. The pretreatment resulted in the enhancement of mesophilic anaerobic digester performance which in turn improved biogas production capacity and quality, total and volatile solid reduction, dewaterability, protein solubilisation and significant reduction of pathogens to produce class A biosolid. This study presented the results of two continuously stirred mesophilic anaerobic digesters charged with various proportions of a mixture of PTEAS and PS similar to the large-scale industrial practice. Digester 1 was charged with 75 % PTEAS and 25 % PS, while digester 2 was fed with 25 % PTEAS and 75 % PS. The methane production was 122 mL CH₄/g total chemical oxygen demand for digester 2 after 20 days of anaerobic digestion. This amount further increased for both digesters with digestion time. The biogas quality in terms of methane to carbondioxide ratio (CH₄/CO₂) was significantly improved for digester 1 compared with digester 2 after 20 days of digestion. Volatile solid reduction of 76 and 57 % was achieved for digester 1 and digester 2 respectively after the same 20 days of digestion. The CH₄/CO₂ ratio reached 2.2:1 and 1.1:1 after 20 days of digestion for digester 1 and digester 2, respectively. Higher percentage of PTEAS increases the digestion kinetics, the methane production capacity and the biogas quality. Furthermore, total coliform reduction of 84 and 44 % was achieved for digester 1 and digester 2 respectively after 22 days of digestion. Hydrolysis rate and biochemical methane production were improved for both digesters based on the results of Gompertz kinetic model and the hydrolysis rate constants as determined by model fitting of the experimental data.

The majority of the existing water bodies around the world are increasingly polluted with oily wastewater. The aim of this study was to investigate the role of single protozoan isolates (Aspidisca, Trachelophyllum and Peranema) and of a consortium of these three protozoan isolates in the biodegradation of fats and oils present in polluted domestic wastewater. The biomass of protozoan isolates, chemical oxygen demand (COD), dissolved oxygen (DO) and concentrations of fats and oils were determined in triplicate before and after the inoculation of isolates in oily wastewaters, using standard methods. Results revealed optimum growth of protozoan cell densities under favourable conditions of 30 °C, pH 6 and 8 (from 1.00 to 4.00, 3.96, 3.80 and 4.20 × 10²cells/ml for Aspidisca, Trachelophyllum, Peranema and a consortium of the three isolates, respectively). The average percentage uptake of DO by Aspidisca, Trachelophyllum, Peranema and their consortium was 95, 96, 96 and 100 %, respectively, for both 30 and 25 °C and at pH levels of (4, 6, 8 and 10), respectively. The results revealed that the COD removal rates of the isolates at various pH levels were ≥20 and ≤90 %, respectively, for 30 and 25 °C. At a temperature of 30 °C, the biodegradation capabilities of the isolates ranged from 3.0 to 8.0, 3.0 to 6.0, 7.0 to 11.0 and 8.0 to 22.0 %, while at 25 °C, the biodegradation rates were 3.0 to 6.0, 4.0 to 7.0, 3.0 to 8.0 and 4.0 to 15.0 % for Aspidisca, Trachelophyllum, Peranema and the consortium of these three isolates, respectively.

Disposing of nitrate-containing effluents from seawater-fed intensive aquacultural applications is a major environmental problem. A possible solution is to mix nitrate-rich effluents from marine recirculating aquaculture systems (RASs) with citrate-rich liquid wastes (CLW), a common by-product of the food industry. Where possible, such strategy can alleviate two environmental problems simultaneously, in a cost-effective fashion. However, concerns are often raised regarding secondary pollution stemming from the use of CLW, particularly related to phosphorus and heavy metals. This work showed that both phosphorus and heavy metal were completely absorbed by the bacterial sludge generated in the process, indicating low environmental risk associated with the disposal of the treated effluent to the environment. Operation of continuous stirred-tank reactor (CSTR) single-sludge denitrification reactor with CLW as electron and carbon donor resulted in high nitrate removal efficiency (>95 %) and denitrification rate of up to 1.6 g NO₃-N L⁻¹reactor day⁻¹along with low bacterial biomass yield [0.23 g chemical oxygen demand (COD) new cells g⁻¹COD citrate]. Moreover, the use of CLW was found to be environmentally safe and equally efficient to the use of traditional, costly carbon sources such as methanol and acetic acid, rendering this alternative attractive for treatment of nitrate-rich saline effluents.

Solar Photo-Fenton reaction, using FeSO₄ and H₂O₂, is an effective and energy-efficient advanced oxidation process (AOP) for degradation of pesticides. However, a major environmental concern is whether the net toxicity after the photo-Fenton process is within the tolerance limit of the aquatic plants and animals, since the unreacted pesticide and Fenton’s reagent may impart additional toxicity to the treated water. Here, we report the oxidative removal of dichlorvos pesticide in wastewater by solar photo-Fenton reaction along with the residual toxicity analysis of the treated water on an aquatic alga. It was found that at pH 3, dichlorvos, with an initial concentration of 6.9 × 10⁻⁵ mol L⁻¹, was observed to be fully degraded within a batch time of 120 min, though the corresponding reduction of chemical oxygen demand (COD) was about 53 % signifying incomplete mineralisation. In order to predict the transient concentration profiles of dichlorvos under different initial concentrations, a four-parameter mathematical model was formulated. Additionally, the resultant toxicity was also examined using a model blue-green alga Nostoc sp. Compared to the raw wastewater, the net biomass of chlorophyll-a was found to increase significantly. Respective estimate of the protein concentration also indicated the same trend. Therefore, sunlight-assisted photo-Fenton process may be regarded as an effective and safe technique for the treatment of pesticide-contaminated agricultural wastewater.

A novel plastic optical fiber (POF) sensor was investigated to monitor total suspended solids (TSS) concentration continuously, offering insights into wastewater treatment bioreactors without disturbing them. First, off-line experiments with both anaerobic and aerobic sludge (in concentrations ranging between 0.1 and 8.6 g TSS L⁻¹) were used to establish the exponential relationship of the sensor’s transmitted optical power with TSS concentrations. Attenuation coefficients differed clearly with the type of sludge (1.227–1.274 and 0.456–0.679 for anaerobic and aerobic biomass, respectively) and, in the case of the aerobic sludge, with its coloring. The POF sensor was further used for online monitoring of sludge settling profiles inside a sequencing batch reactor (SBR) that was being operated under a “feast-famine” regime. The turbidity profiles agreed very well with the Boltzmann equation. The Boltzmann dx parameter revealed clear differences in the steepness of the settling gradients, which could be explained by the changes in the applied organic loading rates (OLR). OLR in the range of 1.34–1.53 g COD L⁻¹ day⁻¹ resulted in steeper settling gradients than OLR in the range of 2.13–3.12 g COD L⁻¹ day⁻¹ (dx: 0.42–0.50 vs. 0.90–1.36). Thus, the POF sensor not only revealed elevated potential for prediction of biomass concentration but also for becoming an integral part of real-time automation systems in order to diminish repeated sampling and off-line analysis to control the withdrawal phase based on seasonal sludge settling profiles.

The study provided a critical appraisal of the extended aeration process as a single-sludge system for nitrogen removal, emphasizing its inherent deficiencies. For this purpose, the system was designed first using the prescribed procedure in the German practice, ATV A-131. The design used the basic data reported in different studies related to conventional characterization and chemical oxygen demand (COD) fractionation defining the biodegradation characteristics of domestic wastewater. A critical appraisal of the design was made with emphasis on the fate of biodegradable COD and oxidized nitrogen in the anoxic phase by process modeling and evaluation. The results obtained were evaluated using basic stoichiometry and mass balance for major nitrogen fractions. The A-131 design based on a total sludge age of 20 days defined a system with a hydraulic residence time of 1.2 days where half of the volume was operated under anoxic conditions; the effluent nitrate concentration was reduced to 8.3 mg N/L with an internal recycle (nitrate) ratio of 4.9. Model evaluation of the prescribed design indicated that oxidized nitrogen was totally consumed within the first 25–30 % portion of the anoxic volume. The remaining volume was forced to operate under anaerobic conditions, where no appreciable endogenous decay would occur. ATV A-131 procedure, relying on empirical coefficients and expressions, was neither consistent with process stoichiometry nor justifiable by modeling. Evaluations based on modeling and process stoichiometry revealed significant inherent weaknesses of extended aeration for providing a sustainable basis for nitrogen removal.