The Hydrochar Characters of Municipal Sewage Sludge Under Different Hydrothermal Temperatures and Durations

Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation （HTC） shows some potential advantages for using hydrochar as a soil conditioner. The aim of this work was to investigate the properties of hydrochars, by means of the HTC of municipal sewage sludge under different temperatures （190 and 260~C） and reaction hours （1, 6, 12, 18 and 24 h）. The HTC led to the decreases of N, O and H contents by more than 54.6, 37.9 and 10.0%, respectively, and slight changes of C content. The Py-GC-MS analysis showed that a large proportion of fatty acids, in particular hexadecanoic acid, transferred into alkenes, olefins and aromatic compounds. The 13C-NMR and fourier transform infrared spectra （FTIR） confirmed the transformation and changes in chemical structure in which hydrochar contained lower oxygen-containing organic C of O-alkyl, carboxylic and carbonyl C and aliphaticity, but higher aromatic C and aromaticity. The rich hydrophobic functions induced in high positive charges in the charred sludge. The HTC facilitated the pore structure development, proved by higher specific surface area and specific pore volume, with a maximum of 17.30 and 0.83 cm^3 g^-1, respectively. The availabilities of N, P and K markedly reduced during HTC treatment. The activities of most heavy metals were depressed though they accumulated in the hydrochar. Further work is required to investigate the values and risk of the charred sludge amended to soil.

Long-term impact of municipal sewage irrigation on treated soil and black locust trees in a semi-arid suburban area of Iran

The effects of municipal sewage irrigation on the soil and black locust （Robinia pseudoacacia L.） tree were studied. For this purpose, two artificial black locust stands under irrigation of municipal sewage and well water were selected in south of Tehran, Iran. Data were collected using technique of systematic random sampling with 4 replicates in each stand. It was found that the growth of black locust tree, as indicated by diameter at breast height, total height, crown length, average crown diameter, basal area and volume, in sewage irrigation stand was much higher than that of well water irrigation stand （P 〈 0.01）. Plant analysis indicated that concentrations of leaf nutrients （N, E K, Ca, Mg, Na, Fe, Mn, Cu and Zn） were greater in sewage-irrigated trees, without toxicity to the minerals of tree leaf, than those of well waterirrigated trees, and positively correlated with their respective value in soil. Ni, Cr and Pb were not detected in leaf samples. Application of sewage resulted in a 1.5-fold increase in the concentrations of soil nutrients, Ni, Cr and Pb. Among these minerals only Pb and Ni in some soil samples exceeded the toxicity limit. The increase in pH, electrical conductivity （EC） and organic carbon of soil was also observed in sewage irrigation. Results confirm that besides the use as irrigation water, municipal sewages are also a potential source of plant nutrients. However, significant accumulation of heavy metals such as Pb and Ni in soil needs to be monitored.

Static aerobic composting of municipal sewage sludge with forced ventilation:Using matured compost as bulking conditioner

Static aerobic composting of municipal sewage sludge with forced ventilation or air ventilation using matured compost as bulking conditioner was investigated. Physical and chemical parame ,eters, e.g., temperature, moisture content, VSS, CODcr, pH, and germination index （GI）, were analyzed to characterize the composting process. Fermentation starts quickly in both forced and air ventilation compost heaps and reaches high-temperature stage after 2 d, owing to the bulking function of matured compost. Compared to air ventilation, however, forced ventilation enables the high-temperature stage to last longer for approximately 7 d. The moisture content of both compost bodies decreases from 62% to about 50% as a result of evaporation, and it decreases slightly faster in forced ventilation compost heap after 13 d due to the higher temperature and better ventilation condition. Although no obvious differences of VSS and pH are observed between both compost heaps, the soluble CODcr and GI show differences during the second half period of fermentation. In forced ventilation compost, the soluble CODcr has a small rebound after 13 d, and GI decreases from 46% to 35% but then increases. These results show that in general, the matured compost is a good conditioner and force ventilation with a proper air supply strategy can be more efficient than air ventilation.

Greenhouse gas emissions from a constructed wetland for municipal sewage treatment

The fluxes of greenhouse gases (methane and nitrous oxide) emission from a constructed wetland in the Eastern China as municipal sewage treatment were measured from June 1999 to August 2000 by the closed chamber method. The constructed wetland for municipal sewage treatment is a significant source of methane, up to 976 6×10 6 g CH 4/a, which was emitted from the constructed wetland with the area of 495000 m 2 and wastewater loading rate of 12000 m 3/d. Its daily mean methane flux reached 5 22 g CH 4/(m 2·d), 250 times as much as that in natural wetland in the same latitude region. 227 8 mg CH 4 was produced from the treatment of 1 liter wastewater, up to 700—1000 times as much as that in the secondary treatment. The emission of nitrous oxide from the constructed wetland is not higher than that from secondary treatment of wastewater, only 0 07 mgN 2O/L.

Effects of Municipal Sewage Sludge on Fixation of Cr,Ni,Cu,and Zn during Co-processing of Heavy Metal-containing Waste in Cement Kilns

Cement raw meal with MSS and different heavy metals was blended to examine the fixation ratios, chemical species, and cement crystalline phases in clinkers. The results showed that blending MSS could decrease the fixation ratio of Cr, Ni, Cu, and Zn in the produced clinker by 5% to 25%. And Cr, Cu, and Zn were mainly incorporated into clinkers as metal silicates, Ni was mainly solubilized in Mg O to form magnesium nickel oxides, and the transition phases were mainly metal aluminum oxides as indicated by X-ray diffraction. The reduction of fixation ratios was likely attributed to the presence of impure elements, such as sodium and phosphorus in MSS. In addition, high concentrations（eg, 1.7 wt%） of chlorine in MSS led to metal chloride formation that could vaporize Cu, Cr, Ni, and Zn. To summarize, introducing MSS would decrease the fixation ratios of heavy metals due to the presence of impure elements, such as sodium and phosphorus and chlorine.

Removal of phosphate from municipal sewage by high gradient magnetic separation

The removal of phosphate from municipal sewage by high gradient magnetic separation using aluminium sulphate as precipitating agent and Fe3O4 as seeding material was studied. The effects of aluminium sulphate, Fe3O4, magnetic field intensity, pH value and flow-rate of sewage on phosphorus removal rate were investigated. The results show that addition of 200 mg/L Al2（SO4）3·18H2O and 300 mg/L Fe3O4, magnetic field intensity of 200 kA/m, pH value of 4.57.0 and flow-rate of 6.15 cm/s are both efficient and economic technical parameters for removal of phosphate. The pH value has a tremendous effect on the removal of phosphate. In the pH range of （4.5）7.0, more than 95% phosphate can be removed. Theoretical analysis indicates that the solubility of AlPO4 is minimum at pH 4.07.0 and the electrostatic attractive force between AlPO4 and Fe3O4 is maximum at pH 4.5（6.5.）

Utilization of coal fly ash and municipal sewage sludge in agriculture and for reconstruction of soils in disturbed lands： results of case studies from Greece and China

Coal fly ash （CFA） and municipal sewage sludge （MSS） management is a great concern worldwide. An alternative gaining high interest, is their use in agriculture and for reclamation of degraded lands. The purpose of this paper was to present very briefly the results of some case studies carried out in China and Greece related to land reclamation and agricultural use of CFA and MSS separately or combined. An experiment in Platanoulia area, central Greece showed clearly that CFA applied together with MSS at appropriate rates increased substantially wheat grain and biomass yield and improved soil quality （increased soil pH, organic matter content, total nitrogen, available P and boron）. In a long-term experiment carried out in Huaibei city, Anhui province, China with a reconstructed soil in a subsided land by using CFA, it was found that physicochemical characteristics （infiltration rate, bulk density, total nitrogen, available P and extractable K） tended to be improved over time. In another experiment in Rodia area central Greece, MSS application improved soil quality of limestone mining spoils from bauxite mining activities. Several other experiments with MSS in Greece showed a clear positive effect on cotton and maize yield and on soil quality.

Development of a novel modified EGSB reactor for municipal sewage treatment at ambient temperatures

A novel modified expanded granular sludge bed(EGSBm) reactor was developed for anaerobic treatment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB(EGSBc) reactor.Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26 ℃.At an upflow liquid velocity(Vup) of 10.3 m/h,the mean concentrations of filtrated COD(CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L,respectively,which were significantly lower than those of the EGSBc effluent operated under identical experimental conditions.When the organic loading rate was suddenly increased from 1.2 to 7.2 kg COD/(m3·d),the EGSBm regained the removal efficiency of previous operation phase in 10 d.Hydrodynamic characteristics of the reactors were compared using the residence time distribution(RTD) model.It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased.The polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm.Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm,moreover,several new species occurred.

CANON Process for Nitrogen Removal from Effluents of Municipal Sewage Treatment Plants

The feasibility and performance of nitrogen removal from municipal sewage were investigated through the completely autotrophic nitrogen removal over nitrite (CANON) process in a continuous reactor. CANON process was successfully started up with the transformation of nitrogen into gas by mass-balance analysis. For the synthetic waste-water (up to 480 mg NH4+-N/(L·d)), removal rates of the ammonia nitrogen and total nitrogen (TN) were about 80% and 55%, respectively, at 1.25 h hydraulic retention time (HRT). For the secondary effluent of municipal sewage, the effluent concentrations of NH4+-N and TN were below 5 mg/L and 9 mg/L, respectively. It is in accordance with the water quality standard for scenic environment with the reuse of urban recycling water (GB/T 18921-2002).

Kinetics of municipal sewage degradation in EGSB and UASB reactors at 10 ℃

Kinetics of municipal sewage degradation in Expanded Granular Sludge Bed(EGSB)and Up-flow Anaerobic Sludge Blanket(UASB)reactors at 10℃ were investigated via continuous experimental equipments.The results indicated that the whole reaction process can be simulated by the first-order dynamic equation model.Dynamic parameters such as k,Vmax and Ks of UASB in hydrolysis acidification stage were 1.08 d-1,2.8 d-1 and 372 mg/L comparing to those of 1.18 d-1,3.5 d-1 and 112 mg/L in the methanogenesis stage respectively.The EGSB’s k,Vmax and Ks were 2.91 d-1,14.3 d-1 and 470 mg/L in the hydrolysis acidification stage comparing to those of 1.68 d-1,6.6 d-1 and 103 mg/L in the methanogenesis stage respectively.Comparison of k values of the two stages in UASB and EGSB indicates that hydrolysis acidification stage is the controlling step for the whole reaction process of UASB,while methanogenesis stage is the controlling step in EGSB.Compared with UASB,municipal sewage treatment by EGSB at 10 ℃ can reach the same effluent requirement with lower retention time due to its effluent recirculation.

A preliminary study on total removal efficiency of organic pollutants in sewage by Harbin municipal sewage treatment plant

To evaluate the removal efficiency of organic pollutants in the sewage by Harbin municipal sewage treatment plant, the influent and effluent samples from the plant were pretreated by liquid-liquid extraction （LLE） under conditions of acidity, neutrality and alkaleseence in sequence, and then were analyzed by gas chromatograph-mass spectrum （GC-MS） procedures. Results indicate that there are 70 species of organic pollutants in the influent sample of the plant, which mainly consist of alkyls, benzene series, esters, and heteroeyclic compounds. Some of these organic pollutants are biotoxie and belong to persistent organic pollutants （POPs）. Four species among them are on the list of Prior Pollutants of Environmental Protection Agency of USA （USEPA）. However, 7 species of organic pollutants appearing in the effluent sample mainly include alkyls of multi-carbons and phthalate esters. The removal efficiency of phthalates is poor because of their poor biodegradability. The sewage treatment technique is effective in removing most＋of organics pollutants.

Characterization, treatment and releases of PBDEs and PAHs in a typical municipal sewage treatment plant situated beside an urban river, East China

Characterization, treatment and releases of eight polybrominated diphenyl ethers （PBDEs） congeners and sixteen polycyclic aromatic hydrocarbons （PAHs） in wastewater were evaluated along the treatment processes of a typical secondary treatment municipal sewage treatment plant （STP） （in Hefei City） situated the beside Nanfei River, East China. The findings showed that the average concentrations of the total PBDEs in raw wastewater and treated effluent were 188.578 and 36.884 ng/L respectively. Brominated diphenyl ether （BDE） 209 congener, the predominant PBDE in the STP and Nanfei River, could be related to the discharge of car-industry-derived wastes. For PAHs, the average concentrations in raw wastewater and treated effluent were 5758.8 and 2240.4 ng/L respectively, with naphthalene, benzo[a]pyrene and indeno[1,2,3-c,d]pyrene being detected at the highest concentrations. PAHs mainly originate from the combustion of biomass/coal and petroleum. The STP reduced about 80% of the PBDEs and 61% of the PAHs, which were eliminated mainly by sedimentation processes. The removal rates of PBDEs/PAHs increased with the increase of their solid-water partitioning coefficients. Accordingly, the STP＇s effluent, containing some PBDE congeners （e.g., BDE 47, 99 and 209, etc.） and low-molecular-weight PAHs, could be an important contributor of these contaminants＇ input to Nanfei River. It resulted in a significant increase of PBDE/PAH concentrations and PAH toxicological risk in the river water downstream. About 4.040 kg/yr of PBDEs and 245.324 kg/yr of PAHs could be released into the Nanfei River. The current conventional wastewater treatment processes should be improved to remove the relatively low-molecular-weight PBDEs/PAHs more effectively.

Trophic transfer of mercury and methylmercury in an aquatic ecosystem impacted by municipal sewage effluents in Beijing, China

Gaobeidian Lake, located in Beijing, China, serves as a recipient lake for efluents from a large municipal sewage treatment plant （MSTP）. In order to evaluate the effects of discharging MSTP efluent on the mercury contamination of the local aquatic ecosystem, sediment cores, water, plankton, fish, and turtle samples were collected from Gaobeidian Lake for mercury speciation analysis. High concentrations of total mercury （T-Hg） were detected in sediment cores （5.24–17.0 μg/g dry weight （dw）, average： 10.1 μg/g）. The ratio of methylmercury （MeHg） to T-Hg was less than 0.3% in sediments and ranged from 35% to 76% in biota samples. The highest level of T-Hg and MeHg were found in aquatic bryophyte and crucian carp （3673 and 437 ng/g dw, respectively）. The relative contents of MeHg were significantly correlated with trophic levels （R2 = 0.5506, p 0.001）, which confirmed that MeHg can be bio-transferred and biomagnified via food chain in this aquatic ecosystem.

Influence of dissolved organic matter on methylmercury transformation during aerobic composting of municipal sewage sludge under different C/N ratios

Current knowledge about the transformation of total mercury and methylmercury(Me Hg) in aerobic composting process is limited. In this study, the composition and transformation of mercury and dissovled organic matter(DOM) in aerobic composting process of municipal sewage sludge were were comprehensively characterized, and the differences among the three C/N ratio(20, 26 and 30) were investigated. The main form of mercury in C/N 20 and 26 was organo-chelated Hg(F3, 46%-60%);while the main form of mercury in C/N 30 was mercuric sulfide(F5, 64%-70%). The main component of DOM in C/N 20 and 26 were tyrosine-like substance(C1, 53%-76%) while the main fractions in C/N 30 were tyrosine-like substance(C1, 28%-37%) and fulvic-like substance(C2, 17%-39%). The mercury and DOM varied significantly during the 9 days composting process. Compared to C/N 20 and 26, C/N 30 produced the less Me Hg after aerobic composting process, with values of 658%(C/N 20), 1400%(C/N 26) and 139%(C/N 30) of the initial, respectively. Meanwhile, C/N 30 produced the best compost showed greater degree of DOM molecular condensation and humification. Hg fraction had been altered by DOM, as indicated by a significant correlation between mercury species and DOM components. Notably, C/N 30 should be used as an appropriate C/N ratio to control the methylation processes of mercury and degration of DOM.

Improved Denitrification of Municipal Sludge in Biofilm-electrode Reactor

The denitrification of municipal sludge was improved by combining biofilm process with the electro-chemical effect in a single novel reactor. Experiments in this reactor[electric current 60 mA, hydraulic retention time(HRTs) 6.0 h] showed that the removal of COD_ Cr, ammonia nitrogen and total nitrogen in the biofilm-electrode reactor were 2.5%, 1.2%, 14.9%, respectively, higher than those in a traditional biofilm reactor.

Spatial Distribution of Heavy Metals in Surface Sediments of the Sakumo Lagoon, Ghana

The aim of this study was to determine the possible build up of heavy metals （Pb, Cu, Fe, Mn and Zn） in the Sakumo lagoon, a Ramsar site situated 3 km west of Tema, an industrial town in Ghana. To achieve this, surface sediments were collected from three sections designated as south, centre and north of the lagoon. Sampling was done for a period of six months （September 2007 to February 2008） and concentrations of the heavy metals （Pb, Cu, Mn, Fe and Zn） in the sediments were determined using the atomic absorption spectrophotometer. The results were compared with the mean concentrations of these metals from a study carried out on the same lagoon in 2003. It was observed that concentrations of these heavy metals in the sediments showed a significant increase over the 2003 levels except for lead where a decrease was observed. The metals also showed spatially large variation from south to north. The spatial variations in concentrations indicate the different absorption capacities of the sediments in the lagoon, a phenomenon which shows that recent anthropogenic heavy metal pollution had occurred. Statistical analysis also showed significant correlation between Pb and Cu （0.968） at 0.01 confidence level and between Cu and Zn （0.869） at 0.05 confidence level.

Sewage sludge ditch for recovering heavy metals can improve crop yield and soil environmental quality

The treatment and disposal of municipal sewage sludge(MSS)is an urgent problem to be resolved in many countries.Safely using the nutrients within MSS to increase crop yield and enhance the fertility of poor soil could contribute to achieving sustainable development.An indirect use of MSS in ditches alongside Pennisetum hybridum plants was studied in field plots for 30 months and the contents of heavy metals and macronutrients were monitored in soil,sludge and plant samples.We found that the yield of P.hybridum was significantly increased by 2.39 to 2.80 times and the treated plants had higher N content compared with no sludge.In addition,the organic matter(OM)and N contents in the planted soil increased significantly compared with the initial soil.The OM content in the planted soil of the MSS treatment was 2.9 to 5.2 times higher than that with no sludge,and N increased by 2.0 to 3.8 times.However,MSS had no significant effect on the N,P and K contents in the soil at the bottom of the MSS ditch,and the content of heavy metals(Cd,Pb,Cu and Zn)were also within the safe range.Moreover,the moisture content and phytotoxicity of MSS after this indirect use were reduced and the heavy metal contents changed little,which is favorable to the further disposal of recovered MSS.Therefore,this indirect use of MSS is beneficial to agricultural production,soil quality and environmental sustainability.

Control of membrane fouling during hyperhaline municipal wastewater treatment using a pilot-scale anoxic/aerobic-membrane bioreactor system

Membrane fouling limits the effects of long-term stable operation of membrane bioreactor （MBR）. Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale anoxic/aerobic-membrane bioreactor （A/O- MBR, 40 L/hr） was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin, China. Impact factors including mixed liquid sludge suspension （MLSS）, sludge viscosity （Ix）, microorganisms, extracellular polymeric substances （EPS）, aeration intensity and suction/suspended time on membrane fouling and pollution control were studied. The relationships among various factors associated with membrane fouling were analyzed. Results showed that there was a positive correlation among MLSS, sludge viscosity and trans-membrane pressure （TMP）. Considering water treatment efficiency and stable operation of the membrane module, MLSS of 5 g/L was suggested for the process. There was a same trend among EPS, sludge viscosity and TMP. Numbers and species of microorganisms affected membrane fouling. Either too high or too low aeration intensity was not conducive to membrane fouling control. Aeration intensity of 1.0 m3/hr （gas/water ratio of 25：1） is suggested for the process. A long suction time caused a rapid increase in membrane resistance. However, long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface. The suction/suspended time of 12 min/3 rain was selected for the process. The interaction of various environmental factors and operation conditions must be considered synthetically.

A CLEAN MOTHER RIVER

The Yangtze’s environmental protection is paramount regardless of its economic development The Yangtze River,flowing more than6,300 km across China,has been witness to many epic events,inspired numerous idyllic poems,and nurtured a large number of booming towns during the country’s long history.