Recovery of phosphorus, magnesium, and potassium from surplus activated sludge using existing sludge treatment facilities and thickened primary sludge.

The separation of P, K, and Mg from surplus activated sludge (SAS) was investigated using existing sludge treatment facilities and the thickened primary sludge (TPS). The addition of the TPS to the SAS storage tank accelerated the anaerobic release of the three elements from SAS with maximum efficiencies of about 60%. The efficiency of P release showed a significant correlation with the oxidation-reduction potential. Increasing the total solid concentration increased the release of elements. The released elements could be transferred to a separate liquid (SL) from a screw-press thickener, and maximum concentrations of P, K, and Mg were about 200, 60, and 35 mg/L, respectively. The addition of CaCl2 and NaOH solutions to SL precipitated P as hydroxyapatite. However, no precipitation of K and Mg occurred simultaneously with P, even when the pH of SL was increased to 9. These findings suggest that about 60% of P, K, and Mg can be separated from SAS into SL using existing sludge treatment facilities and TPS; however, a method other than precipitation would be needed to recover P and K from SL simultaneously.

Exploration of an efficient method for removing antibiotics from water and digested sewage sludge using Fe(VI): Kinetics and P phytoavailability and compostability in treated sludge.

Potassium ferrate (K2FeO4) containing hexavalent iron [Fe(VI)] is an environmentally friendly oxidant, which possesses strong oxidizing power to treat wastewater and sludge. Therefore, the present study investigated degradation of selected antibiotics, namely levofloxacin (LEV), ciprofloxacin (CIP), oxytetracycline (OTC), and azithromycin (AZI), in water and anaerobically digested sewage sludge samples using Fe(VI). The effects of different Fe(VI) concentrations and initial pH values on antibiotic removal efficiency were evaluated. Under the studied conditions, LEV and CIP were almost completely removed from water samples, following second-order kinetics. In addition, over 60% of the four selected antibiotics were removed from sludge samples using 1 g L-1 Fe(VI). Furthermore, P phytoavailability and compostability of Fe(VI)-treated sludge were evaluated using different extraction reagents and a small composting unit. The extraction efficiency of phytoavailable P using 2% citric acid and neutral ammonium citrate was approximately 40% and 70%, respectively. The mixture of Fe(VI)-treated sludge and rice husk was self-heated in a closed composting reactor through the biodegradation of organic matter derived from the treated sludge. Therefore, Fe(VI)-treated sludge may be used as an organic material containing phytoavailable P for compost.

Degradation of sulfamonomethoxine in solution using pulsed plasma discharge - identification of by-products and toxicity of treated solution to green algae.

This study investigated the degradation of sulfamonomethoxine (SMM) by pulsed plasma discharge. SMM was successfully degraded following the first-order kinetics model. The percentage removal of SMM was estimated by the total input energy of plasma discharge, which was dependent on the initial SMM concentration. In addition, three types of by-products were observed at an early reaction time, which were then degraded. In contrast, the ecotoxicity of the treated solution by plasma discharge was assessed by an acute toxicity test using the green alga Raphidocelis subcapitata. The plasma discharge in water generated hydrogen peroxide with a concentration higher than the EC50 for R. subcapitata. It is therefore necessary to remove H2O2 or prevent the generation of H2O2 for the degradation of antibiotics in solutions using plasma discharge.

Degradation of the endocrine-disrupting 4-nonylphenol by ferrate(VI): biodegradability and toxicity evaluation.

4-Nonylphenol (4-NP) is an endocrine-disrupting and persistent chemical and is partially degraded in conventional wastewater treatment processes. Ferrate(VI) can be used as an environment-friendly oxidizing agent to mediate 4-NP degradation. Thus, this paper evaluates the biodegradability of 4-NP and its degradation products after the addition of ferrate(VI). The biodegradability was examined using NP labeled with 14C as a tracer and activated sludge microorganisms as an inoculum. The addition of ferrate(VI) to the 4-NP solution spiked with the tracer resulted in no remarkable decrease in the concentration of 14C, indicating incomplete mineralization of 4-NP and formation of degradation products. The degradation products from 4-NP with Fe(VI) were estimated based on mass spectra, which detected a unique peak at m/z 223 at low intensity. Four hydrogen atoms might have been added to 4-NP by degradation with Fe(VI). In addition, the effect of ferrate(VI) concentration on the estrogenic activity of 4-NP in an aqueous solution was investigated using a yeast bioassay. The results show that estrogenic activity was significantly decreased at a mass ratio of Fe(VI) to 4-NP greater than or equal to 2.5.

Effect of dissolved soil organic matter on cesium adsorption by zeolite and illite.

In controlled landfill sites, soil layers are installed around radioactive waste to prevent the leaching of radioactive cesium (Cs). The Cs retention capacity of soil has been reported to be enhanced by mixing clay minerals. However, several studies have indicated that dissolved soil organic matter (DSOM) inhibits the Cs sorption by clay minerals. Therefore, this study assesses the effect of DSOM on the Cs sorption by zeolite and illite. Excitation emission matrix fluorescence spectroscopy was used for DSOM in the soil solution before and after contact with clay minerals. The results show that DSOM sorption onto clay minerals, particularly fulvic acid, inhibited Cs sorption. Batch sorption tests were conducted to obtain the sorption isotherms using two sample solutions, namely, soil and ionic solutions. Soil solution, which contained DSOM, was prepared by mixing soil and ultrapure water and filtration using a 0.3-µm glass fiver filter. Ionic solution was prepared by removing DSOM larger than 500 Da from the soil solution using dialysis. The amount of sorbed Cs in the soil solution was lower than that in the ionic solution. Comparing the Freundlich coefficients (KF) between the soil and ionic solutions, we found that the KF values of zeolite and illite for the ionic solution accounted for 6.4- and 4.4-fold higher than that for the soil solution, respectively.

Tylosin degradation during manure composting and the effect of the degradation byproducts on the growth of green algae.

In this study, we investigate the tylosin degradation in sheep feces during composting. The sheep feces containing tylosin were composted using the laboratory-scale composting units. Tylosin was degraded during composting, and the half-life of tylosin degradation decreased with increasing temperature from 40 °C to 65 °C. The tylosin degradation in sheep feces can be attributed to the microorganisms in the feces and not to heating because tylosin did not degrade over a period of 48 h at temperatures of 0 °C-65 °C in sterilized water. The artificial rainwater solution extracted from the composted sample did not inhibit the growth of Raphidocelis subcapitata, a type of green alga. Our results indicate that composting the feces containing tylosin is effective in degrading tylosin, which may result in the preservation of agricultural fields as well as nearby aquatic environments.

Removal of nonylphenol and nonylphenol monoethoxylate from water and anaerobically digested sewage sludge by Ferrate(VI).

Nonylphenol (NP) and nonylphenol monoethoxylate (NP1EO) have toxic and persistent characteristics, and are incompletely degraded in conventional wastewater treatment processes. These compounds are present in sewage sludge that can be reused as fertilizers or soil conditioners. Accordingly, NP and NP1EO should be properly removed before being discharged in the environment. In this study, potassium ferrate (K2FeO4) containing hexavalent iron (Fe(VI)) was used as an environment-friendly oxidizing agent to mediate NP and NP1EO degradation. The aim of this study was to investigate the effects of pH and Fe(VI) dosage on the degradation of NP and NP1EO in water and anaerobically digested sewage sludge samples. In water samples, under conditions examined in this study, maximum removal efficiencies for NP and NP1EO were 98% and 92%, respectively. For digested sewage sludge samples, the maximum removal efficiencies of NP and NP1EO were 58% and 96%, respectively. The results demonstrated that Fe(VI) can potentially degrade NP and NP1EO in water and digested sewage sludge samples. However, organic matter as a matrix in the sludge sample would inhibit the degradation of NP and NP1EO by Fe(VI). The pH values before and after adding K2FeO4 to the samples had an obvious influence on the removal of NP and NP1EO.

Determination of tylosin excretion from sheep to assess tylosin spread to agricultural fields by manure application.

Antibiotics administered to livestock are partly excreted with urine and feces. As livestock excrement is used as manure on agricultural fields, soil may be contaminated by excreted antibiotics, potentially resulting in the development of antibiotic-resistant bacteria. Therefore, it is necessary to determine the amount of antibiotic administered to livestock that could spread to agricultural fields through manure application. This study reveals the excretion ratio of tylosin from sheep. After developing an analysis procedure for tylosin in urine and feces from sheep, a tylosin excretion study was performed with two sheep. Tylosin was excreted in urine and feces for four days, after which its concentrations dropped below the limits of quantification (urine: 0.5µg/kg, feces: 2.4µg/kg). The total excretion ratio was 11% on average. The results of our study can provide useful knowledge for treating excrement in order to prevent the spread of antibiotics to agricultural fields through manure application.

Cesium and strontium loads into a combined sewer system from rainwater runoff.

In this study, combined sewage samples were taken with time in several rain events and sanitary sewage samples were taken with time in dry weather to calculate Cs and Sr loads to sewers from rainwater runoff. Cs and Sr in rainwater were present as particulate forms at first flush and the particulate Cs and Sr were mainly bound with inorganic suspended solids such as clay minerals in combined sewage samples. In addition, multiple linear regression analysis showed Cs and Sr loads from rainwater runoff could be estimated by the total amount of rainfall and antecedent dry weather days. The variation of the Sr load from rainwater to sewers was more sensitive to total amount of rainfall and antecedent dry weather days than that of the Cs load.

Fate of radiocesium in sewage treatment process released by the nuclear accident at Fukushima.

The nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) which occurred after the Great East Japan Earthquake on March 11, 2011 resulted in releases of radionuclides such as (134)Cs (half-life:T1/2=2.06 yr), (137)Cs (T1/2=30.04 yr) and (131)I (T1/2=8.05 d) to the environment. For this paper, we observed the monthly variations of radiocesium ((134)Cs and (137)Cs) and stable Cs concentrations in influent, effluent, sewage sludge, and sludge ash collected from a sewage treatment plant 280 km north of the FDNPP from July to December, 2011. Using the stable Cs results, we concluded the mass balance of Cs in the sewage treatment plant showed that about 10% of the Cs entering the sewage treatment plant would be transferred to the sewage sludge, and then Cs in the sewage sludge was totally recovered in the sludge ash. The behavior of Cs was similar to that of Rb, but it was not similar to that of K in the sewage treatment process.

Fate of stable strontium in the sewage treatment process as an analog for radiostrontium released by nuclear accidents.

Radionuclides were widely released into the environment due to the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. Some of these radionuclides have flowed into municipal sewage treatment plants through sewer systems. We have observed the fate of stable Sr in the sewage treatment process as a means to predict the fate of radiostrontium. Concentrations of stable Sr were determined in sewage influent, effluent, dewatered sludge, and incinerated sewage sludge ash collected from a sewage treatment plant once a month from July to December 2011. In the mass balance of Sr in the sewage treatment plant, 76% of the Sr entering the plant was discharged to the receiving water on average. Additionally, 14% of the Sr flowing through the plant was transferred to the sewage sludge and then concentrated in the sludge ash without being released to the atmosphere. We also investigated Sr sorption by activated sludge in a batch experiment. Measurements at 3 and 6h after the contact showed Sr was sorbed in the activated sludge; however, the measurements indicated Sr desorption from activated sludge occurred 48 h after the contact.

Biological oxidation of arsenite in synthetic groundwater using immobilised bacteria.

Biological oxidation of arsenite (As(III)) in synthetic groundwater was examined by using arsenite oxidising bacteria (AOB) isolated from an activated sludge. The phylogenetic analysis indicated that the isolated AOB was closely related to Ensifer adhaerens. Batch experiments showed that for an As(III) oxidation with the isolated AOB the optimum ratio of nitrogen source (NH4-N) concentration to As(III) concentration was 0.5 (52 mg/L-110 mg/L) and the isolated AOB preferred pH values ranging from 6 to 8, and water temperatures greater than 20 °C. Further continuous experiments were conducted using a bioreactor with immobilised AOB. With an initial As(III) concentration of 1 mg/L at a hydraulic retention time (HRT) of 1 h, an As(III) oxidation rate was around 1 × 10⁻9 µg/cell/min and an As(III) oxidation efficiency of 92% was achieved. Although the maximum oxidation rate measured at an HRT of 0.5 h was 2.1 × 10⁻9 µg/cell/min, the oxidation efficiency decreased to 87%. These results advocate that a biological process involving immobilised AOB may be useful as an economical and environmentally friendly pre-treatment step for As removal from groundwater.

Iodide sorption and partitioning in solid, liquid and gas phases in soil samples collected from Japanese paddy fields.

Sorption kinetics of iodide (I(-)), which is one of the major inorganic chemical forms of iodine in soil environments, were studied under four sets of experimental conditions characterised by temperature or biological activity. We compared partitioning ratios in solid, liquid and gas phases in soils as well as soil-soil solution distribution coefficients (K(d)s) at two different temperatures 4 and 23 °C, for 63 paddy soil samples collected throughout Japan. Interestingly, (125)I emission from soil was observed; the partitioning ratios in gas phase ranged from 0 to 27 % at 4 °C and from 0 to 42 % at 23 °C. In addition, the authors found that K(d) values at 23 °C had good correlation with pH though there was no correlation between K(d) values at 4 °C and pH because of the difference in biological activity.

Estimation of soil-soil solution distribution coefficient of radiostrontium using soil properties.

We propose a new approach for estimation of soil-soil solution distribution coefficient (K(d)) of radiostrontium using some selected soil properties. We used 142 Japanese agricultural soil samples (35 Andosol, 25 Cambisol, 77 Fluvisol, and 5 others) for which Sr-K(d) values had been determined by a batch sorption test and listed in our database. Spearman's rank correlation test was carried out to investigate correlations between Sr-K(d) values and soil properties. Electrical conductivity and water soluble Ca had good correlations with Sr-K(d) values for all soil groups. Then, we found a high correlation between the ratio of exchangeable Ca to Ca concentration in water soluble fraction and Sr-K(d) values with correlation coefficient R=0.72. This pointed us toward a relatively easy way to estimate Sr-K(d) values.

Sorption behavior of selenium on humic acid under increasing selenium concentration or increasing solid/liquid ratio.

The sorption of selenium (Se) on humic acid (HA) was investigated in order to better understand the fate of stable and radioactive Se in soils and sediments. An ultrafiltration technique was used to determine size distributions of HA-sorbed-Se when increasing Se concentration and solid/liquid ratio. The results showed that the Se sorption onto HA followed the Freundlich isotherm. No solid/liquid ratio-dependence was observed especially when <3 kDa molecular size fraction was used from solid/liquid separation. The Freundlich isotherm parameters K(F) and n obtained using the <3 kDa molecular size fraction for solid/liquid separation were 3.7 x 10(2) and 0.82, respectively. In addition, since dissolved HA increased with decreased ionic strength in the HA suspension, ionic strength could promote aggregation of HA. The conformational change of HA could affect the sorption behavior of Se on HA.