Endotoxic material, commonly associated to biological reactions, is thought to be one of the most important constituents in water. This has become a very important topic because of the common interest in microbial products governed by the possible shift to water reuse for drinking purposes. In this light, this study was conducted to provide an assessment of endotoxic activity in reclaimed wastewater. A bacterial endotoxin test (LAL test) was applied to water samples from several wastewater treatment plants (WWTP) in Sapporo, Japan keeping in view the seasonal variation. Samples were taken from several points in WWTP (influent, effluent, return sludge, advanced treatment effluent). The findings of this study indicated that wastewater shows high endotoxin activity. The value of Endotoxin (Endo) to COD ratio in the effluent is usually higher than that of the influent. Moreover, it is found that wastewater contains initially endotoxic active material. Some of those chemicals are biodegradable and but most of them are non-biodegradable. Batch scale activated sludge studies were undertaken to understand the origin of endotoxic active material in the effluent. This study showed that those chemicals are mainly produced during biological reactions, more precisely during decay process. Moreover, raw wastewater (RWW) contains high amounts of organic matter having endotoxicity which remains in the effluent.

Urine is rich in nutrients and can be applied as a fertilizer. The limitation on the application is the transportation cost for the farmlands. The cost estimation required 80% of the volume reduction for a feasible utilization of urine in the farmlands near urban areas. The volume reduction system by forward osmosis (FO) process was proposed to address this problem. In this study, the experiments on FO process with real and synthetic hydrolysed urine were performed to assess the FO performances, to evaluate the solute diffusion and to describe the water flux considering the activity of solutes. This study showed both real and synthetic urine can be concentrated to 2-5 times with 2-5 mol/L sodium chloride solution. High diffusivity of ammonia and carbonates were observed, but the diffusion of other solutes was low. The activities of the solutes in the non-ideal solution should be considered for estimation of the osmotic pressure of the solution which reflects the water flux. The software PHRE-EQC can be used for estimation of the activities in such high concentration solutions. The organic matter in real hydrolysed urine had a negligible effect on the osmotic pressure variations.

Cyclic voltammetry (CV) was used in this work to describe the electrochemical behavior of a dual-chamber microbial fuel cell (MFC). The system performance was evaluated under vacuum and non-pressurized conditions, different reaction times, two sweep potentials, 25 and 50 mVs−1 and under different analyte solutions, such as distilled water and domestic wastewater. CV experiments were conducted by using a potentiostat with three different configurations to collect the measurements. A dual-chamber MFC system was equipped with a DupontTM Nafion® 117 proton exchange membrane (PEM), graphite electrodes (8.0 cm × 2.5 cm × 0.2 cm) and an external electric circuit with a 100-Ω resistor. An electrolyte (0.1 M HCl, pH ≈ 1.8) was used in the cathode chamber. It was found that the proton exchange membrane plays a major role on the electrochemical behavior of the MFC when CV measurements allow observing the conductivity performance in the MFC in the absence of a reference electrode; under this potentiostat setting, less current density values are obtained on the scanned window potentials. Therefore, potentiostat setting is essential to obtain information in complex electrochemical processes present in biological systems, such as it is the case in the MFCs. Results of the study showed that wastewater constituents and the biomass suspended or attached (biofilm) over the electrode limited the electron charge transfer through the interface electrode-biofilm-liquor. This limitation can be overcome by: (i) Enhancing the conductivity of the liquor, which is a reduction of the ohmic drop, (ii) reducing the activation losses by a better catalysis, and (iii) by limiting the diffusional gradients in the bulk liquor, for instance, by forced convection. The use of the electrolyte (0.1 M HCl, pH ≈ 1.8) and its diffusion from the cathode to the anode chamber reduces the resistance to the flow of ions through the PEM and the flow of electrons through the anodic and cathodic electrolytes. Also reduces the activation losses during the electron transfer from the substrate to the electrode surface due to the electrode catalysis improvement. On the other hand, vacuum also demonstrated that it enhances the electrochemical performance of the dual-chamber MFC due to the fact that higher current densities in the system are favored.

As wastewater reclamation and reuse becomes more widespread, risks of exposure to treated wastewater increase. Moreover, an unlimited number of pollutants can be identified in wastewater. Therefore, comprehensive toxicity assessment of treated wastewater is imperative. The objective of this study was to perform a comprehensive toxicity assessment of wastewater treatment systems using stress response 10 bioassays. This powerful tool can comprehensively assess the toxicity of contaminants. In this study, samples from conventional activated sludge treatment, membrane bioreactors (MBRs) with different pore sizes and sludge retention times (SRTs), rapid sand filtration, coagulation, nano-filtration (NF) and reverse osmosis (RO) were investigated. The results of stress response bioassays confirmed that the secondary effluent showed higher stress response than influent indicating that biological treatment 15 generates toxic compounds. The results obtained from molecular weight fractionation of water samples demonstrated that organic matter with a higher molecular weight fraction (>0.1μm) causes toxicity in secondary effluent. Furthermore, supernatant from MBR reactors showed toxicity regardless of SRT. On the other hand, stress response was not detected in MBR permeates except for an MBR equipped with a larger pore size membrane (0.4μm) and with a short SRT (12 days). While rapid sand filtration could not 20 remove the toxic compounds found in secondary effluent, coagulation tests, operated at an appropriate pH, were effective for reducing stress response in the secondary effluent. Experimental findings also showed that stress response was not detected in cases of NF and RO permeate subsequent to MBR treatment.

No abstract

No abstract

In this study, we applied the Limulus amebocyte lysate (LAL) test to rejected water samples from a sludge treatment facility in Sapporo, Japan. The endpoint LAL test was performed using a commercial kit and involved incubating a mixture of water samples and LAL reagent at 37 degrees C. We have observed that all of the rejected water showed endotoxic activity. Overflow from thickener and dewatering are the main contributor to this high concentration in the influent of treatment plants receiving return flow from sludge treatment facilities. The LAL test was also applied to sample batch tests, where sewage was mixed with rejected waters and aerated for 12 hours. It was found that the low biodegradability of endotoxic material in the mixture led to higher endotoxicity in comparison to the sewage and sludge aerated without rejected water. Several batch tests were also operated using sewage, sludge and different types of rejected water (overflow from thickener, dewatering, dehumidification, and desulfurization). The findings indicated that samples from reactors using water from thickener and dewatering had significant concentrations and these contributed to the high values of the effluent.

Due to its high salt content, urine use as a fertilizer threatens agricultural land by causing soil sodification, especially in arid and semi-arid lands where limited water resources restrict full salt washout. This study investigated the management of salt accumulation in a soil in which urine was assumed to be previously directly applied as a fertilizer. Since feasibility studies of urine use as a fertilizer have been previously reported in the arid land of Burkina Faso in the Sahel region, we investigated the removal during rainy season using rainfall and evaporation data from Burkina Faso of the salts accumulated in the soil from previous cultivations assumed to be fertilized with urine. Column test experiments were carried out under greenhouse conditions. The experiment involved irrigation of planted and non-planted pots for 56 days with de-ionized water to reproduce the rainy season in Burkina Faso. Prior to the experiments, 400 mg/pot of NaHCO 3 was added to the top 10 cm of the soil columns, simulating the initial salt content in the soil due to the assumed previous irrigation using urine (pH = 7.63). Although, Na salts are the dominant salt in urine, sodium bi-carbonate has been used in this study as it has a buffering capacity to resist to sudden pH changes. The experimental study revealed that a significant portion of salt that accumulated in the column during cultivation is washed out of non-planted pots during the rainy season. In planted pots, the higher evaporation rate led to less washout and more salt accumulation in the soil. Of the original 400 mg/pot, 259 mg/pot was washed out of non-planted pots, while only 80 mg/pot was washed out of planted pots. Another 40 mg/pot was taken up by plants in the case of planted pots. A HYDRUS-1D model was then used to predict the fate of the salts in the soil (non-planted) under different conditions (e.g., variable calcium supply, variable initial Na concentration). Model calibration was performed using data from previous experiments. The application of Ca promoted lower sodic conditions in the soil. A Ca application of 14 g/m 2 is required to free all the remaining sodium salts via the cation exchange mechanism allowing their full washout from the soil.