Uniformity of domestic wastewater effluent application in a subsurface drip distribution system.

An on-site wastewater treatment project with two separate drip fields was operated for 6 years and received no maintenance. The two drip fields (with different design configurations) contained pressure-compensating emitters (PC) and non-pressure-compensating emitters (NPC), respectively, and received wastewater with an average 5-day biochemical oxygen demand concentration of 23 mg/L. Flowrates of the PC emitters reduced from rated average of 3.50 to 1.00 L/h, and the average flowrate of the NPC emitters reduced from 2.00 to 1.53 L/h. The statistical uniformities were 48 and 71%, and the uniformity coefficients were 70 and 86% for PC and NPC emitters, respectively. Significant, but incomplete, recovery was achieved with field-flushing and consecutive shock-chlorination treatments of 500 and 1000 mg/L.     

Optimisation of pressurised liquid extraction for elimination of sulphur interferences during determination of organotin compounds in sulphur-rich sediments by gas chromatography with flame photometric detection

A simple method for species-selective analysis of organotin compounds (OTCs) (butyl and phenyl) in sediments was developed. The sample preparation procedure was specifically optimised for sulphur-rich sediments to eliminate interferences from elemental sulphur and organosulphur compounds. Tin species were extracted from sediment samples using pressurised liquid extraction technique (PLE), ethylated - with simultaneous extraction to isooctane - in aqueous phase with sodium tetraethylborate (NaBEt(4)) and separated/detected by gas chromatography with flame photometric detection (GC-FPD). PLE operational variables (extraction temperature and pressure, solvent composition and number of static extraction steps) and extract handling routine were fine-tuned to minimise the amount of extracted interferents while keeping OTCs recovery at an acceptable level. Best results were obtained after extraction of sediment samples with methanol/water (75% v/v methanol) solution of acetic acid/sodium acetate with tropolone addition (0.6 g l(-1)). Derivatisation of low temperature, high-pressure (50 degrees C, 13.8 MPa) extracts gives isooctane extracts which are clean enough to be directly analysed by GC-FPD without any further cleanup. Interferences from elemental sulphur were completely eliminated while concentrations of other interferents were reduced to the level not impairing quantitation of OTCs under the study. No negative effects in terms of chromatographic column deterioration were observed after repeated injections of such extracts. Two certified reference materials, BCR646 and PACS-2, were analysed to assess performance of the method. Recoveries of all OTCs under the study, except MBT, were in the range of 91-114%. MBT extraction efficiency was low (34-47%) therefore the method is unsuitable for precise determinations of this compound.     

反渗透处理稀土氨氮废水试验研究

根据稀土冶炼厂排放的碳铵沉淀洗涤废水的水质情况,采用NH4Cl和 NaCl模拟废水进行了反渗透可行性对比实验。模拟实验发现,在相同条件下反渗透对NaCl 较NH₄Cl 有着更高的去除率,而NH₄Cl 相对NaCl则有着更高的产水速率。实际废水试验结果表明,在恒定操作压力范围内回收率为65%的条件下,NH₄Cl浓度为2.85 g/L的碳铵沉淀洗涤废水经反渗透处理其NH₄Cl去除率为77.3%,可作为氨氮废水的预处理。对该废水处理成本进行了分析,得出其约为2.7元/m³,比相近浓度氨氮废水的氨吹脱处理成本节省约26%。     

The fate of lindane in the conventional activated sludge treatment process

A pilot-scale treatability study was performed to evaluate the fate of lindane (gamma-hexachlorocyclohexane) in wastewater treatment plants operating in the conventional activated sludge mode. Different types of wastewater (industrial and municipal) spiked with variable lindane concentrations were used at different dosing rates in order to determine distribution and removal under various operational conditions. The major amount (67-91%) of lindane inputs to the treatment process was found to concentrate in primary sludge. A significant linear correlation between the compound's partition coefficient (logKp) and the organic fraction of primary sludge (foc) was found. Sorption on primary sludge solids was concluded to be the major removal mechanism. Only 0.1-2.8% of lindane inputs was concentrated in activated sludge. Lindane losses in primary treatment were low (4-26%). Higher losses (up to 61%) were observed during the biological treatment probably due to biodegradation. These losses were negatively correlated with the inflow rate of lindane into the aeration tank. Activated sludge aged about 23 d presented the maximum loss of lindane. Increased sludge age was associated with increased percentages of lindane in the final effluent.     

Oily wastewater treatment using a novel hybrid PBR-UASB system

In this study, anaerobic treatability of oily wastewater was investigated in a hybrid reactor system consisting of a packed bed reactor (PBR) followed by an upflow anaerobic sludge blanket (UASB) reactor at 35 degrees C. The system was operated using real pet food wastewater at different hydraulic retention times and loading rates for 165 d. The PBR was packed with sol-gel/alginate beads containing immobilized enzyme which hydrolyzed the oil and grease (O&G) into free long chain fatty acids, that were biodegraded by the UASB. The hybrid system was operated up to an oil loading rate of 4.9 kg O&Gm(-3)d(-1) (to the PBR) without any operational problems for a period of 100 d, with COD and O&G removal efficiencies above 90% and no sludge flotation was observed in the UASB. Beads supplement to the PBR was less than 2 g d(-1) and the relative activity was about 70%. Further increment in O&G loading to 18.7 kg O&Gm(-3)d(-1) caused destabilization of the system with 0.35% (v float/v feed) sludge float removed from the UASB.     

The study on the dechlorination of OCDD with Pd/C catalyst in ethanol-water solution under mild conditions

Dechlorination of octachlorodibenzo-p-dioxin (OCDD) was carried out in ethanol-water (v/v=1:1) solution of NaOH in the presence of Pd/C catalysts with the use of H(2). The substrate was dechlorinated with Pd/C under mild conditions (atmospheric pressure and <100 degrees C) to give a chlorine-free product, dibenzo-p-dioxin (DD), in high yields. After reaction of 3h at 50 degrees C, 95.9% OCDD was degraded to low dechlorinated congeners and the yield of DD was 77.4%. We have also studied the dechlorination selectivity of chlorine atoms on the different substituted positions and postulated the dechlorination pathway of OCDD. For OCDD, the 2-position has higher reactivity than 1-position, but the difference is very small. From the distribution statistics of the intermediates during the reaction, we postulate that the steric effect plays an important role during the reaction and affect the dechlorination pathway of OCDD.     

Treatment of refectory oily wastewater by electro-coagulation process

Electro-coagulation was used to treat refectory wastewater with high oil and grease contents. Different operational conditions were examined, including pH, current density, reaction time, conductivity, electrode distance and inlet concentration. The optimum current density was 10-14 A m(-2) within 30 min depending on the wastewater properties tested. Conductivity had little effect on the treatment efficiency. Although the addition of extra salts (e.g., sodium chloride) to the wastewater did not help increase the pollutant removal efficiency, it could save the power consumption significantly. The COD(Cr) and oil removal efficiency descended with increasing electrode distance. The optimal electrode distance was determined to be 10 mm for this equipment in consideration of the treatment cost and efficiency together. The pH effect on the performance of the electro-coagulation process was not very significant in the range of 3-10. The removal efficiency of oil and COD(Cr) under normal condition exceeded 95% and 75%, respectively.     

Catalytic hydrothermal treatment of pulping effluent using a mixture of Cu and Mn metals supported on activated carbon as catalyst

The present study was performed to investigate the performance of activated carbon-supported copper and manganese base catalyst for catalytic wet oxidation (CWO) of pulping effluent. CWO reaction was performed in a high pressure reactor (capacity?=?0.7 l) at temperatures ranging from 120 to 190 °C and oxygen partial pressures of 0.5 to 0.9 MPa with the catalyst concentration of 3 g/l for 3 h duration. With Cu/Mn/AC catalyst at 190 °C temperature and 0.9 MPa oxygen partial pressures, the maximum chemical oxygen demand (COD), total organic carbon (TOC), lignin, and color removals of 73, 71, 86, and 85 %, respectively, were achieved compared to only 52, 51, 53, and 54 % removals during the non-catalytic process. Biodegradability (in terms of 5-day biochemical oxygen demand (BOD₅) to COD ratio) of the pulping effluent was improved to 0.38 from an initial value of 0.16 after the catalytic reaction. The adsorbed carbonaceous fraction on the used catalyst was also determined which contributed meager TOC reduction of 3–4 %. The leaching test showed dissolution of the metals (i.e., Cu and Mn) from the catalysts in the wastewater during CWO reaction at 190 °C temperature and 0.9 MPa oxygen partial pressures. In the future, the investigations should focus on the catalyst reusability.     

Transport of coliphage PRD1 in a surface flow constructed wetland.

A tracer study was conducted in a 3-ha surface flow constructed wetland to analyze transport performance of PRD1, an enteric virus model. The convection-dispersion equation (CDE), including a first-order reaction model, adequately simulated transport performance of PRD1 in the wetland under an average hydraulic loading rate of 82 mm/d. Convective velocity (v) and longitudinal dispersion coefficient (D) were estimated by modeling a conservative tracer (bromide) pulse through the wetland. Both PRD1 and bromide were simultaneously added to the entering secondary treated wastewater effluent. The mass of bromide and PRD1 recovered was 76 and 16%, respectively. The PRD1 decay rate was calculated to be 0.3/day. The findings of this study suggest that the CDE model and analytical moment equations represent a suitable option to characterize virus transport performance in surface flow constructed wetlands.     

NaNO(2)/FeCl(3) catalyzed wet oxidation of the azo dye Acid Orange 7

A combination of ferric chloride and sodium nitrite significantly improved the wet oxidation of the azo dye Acid Orange 7 (AO7) in acid aqueous media (pH 2.6) under moderate conditions (T=150 degrees C; oxygen pressure=0.5 MPa). To evaluate the catalytic system, wet oxidation of AO7 was carried out at temperatures between 90 and 150 degrees C and oxygen pressures ranging from 0.1 to 0.5 MPa. The effect of initial solution pH from 2.6 to 11.4 and the amount of catalyst on the degradation of AO7 were also investigated. AO7 initial concentration was kept 200 mg L(-1). The degradation process was monitored by UV-visible spectroscopy, HPLC, IC (ion chromatography), GC-MS and TOC analysis. At 150 degrees C and 0.5 MPa oxygen pressure, 56% TOC was removed after 4h of treatment, while no obvious TOC removal were achieved without catalyst at the same experimental condition. The main degradation products were some small organic acids: formic acid, acetic acid, pyruvic acid, oxalic acid, succinic acid (identified and quantified by IC) and phthalic acid (identified by GC-MS).     

Composting of wastewater treatment sludge with different bulking agents

The main objectives of this study were to investigate the compostability of wastewater treatment sludge (WTS) containing different bulking agents (BAs) and to determine the most efficient BA. Four different compost trials consisting of mixtures of wheat straw (WS), plane leaf (PL), corncob (CC) and sunflower stalk (SS) with WTS were performed in laboratory reactors. In all experiments, a mixture of 60% WTS and 40% BA (wet basis) was used. The temperature, dry matter (DM), organic matter (OM), pH, electrical conductivity (EC) and C/N ratio were monitored during the composting process. Evaluation of the operational parameters showed that the highest organic matter degradation (i.e. 37.6%), loss of dry matter (i.e. 29.6%) and temperature (i.e. 64 °C) were achieved for the WTS-CC mixtures. Results also showed that the WTS-SS mixture was also successful in terms of these operational parameters. Use of bulking agents for the treatment of wastewater treatment sludge in composting process is an important issue with regards to process efficiency, economy and disposal of agricultural waste. Corncob and sunflower stalk that were previously not used for the composting of WTS from food industry were shown to be highly successful BA materials in this study.

Implications: The compostability of wastewater treatment sludge from the food industry with different bulking agents was studied. Wheat straw, plane leaf, corncob, and sunflower stalk were used as bulking agents. The required microbial stabilization and degree of mineralization were achieved with corncobs and sunflower stalks.     

用氧化铝厂赤泥制备高效混凝剂聚硅酸铁铝

研究了以氧化铝厂赤泥为原料,在常压通氧条件下,用稀硫酸浸取制备高效混凝剂聚硅酸铁铝（PSAF）的方法,确定了合理的生产工艺和操作条件。该混凝剂用于处理工业废水,并与聚合硫酸铁（PFS）的处理效果比较,CODCr和色度去除率分别提高约20％和28％,SS去除率提高约10％,同时,探讨了该混凝剂处理废水的反应机理。     

Effects of experimental parameters on NF(3) decomposition fraction in an oxygen-based RF plasma environment

Clean procedure is one of the major emitters of perfluorinated compounds (PFCs) in semiconductor manufacturing. Nitrogen trifluoride (NF(3)) is increasingly the process gas of choice for eliminating PFC emissions. However, its toxic to human and similar global warming potential compared to most other PFCs made NF(3) warranted much more investigation. This study demonstrated a radio-frequency plasma system for decomposing NF(3). The effects of experimental parameters: input power, O(2)/NF(3) ratio, operational pressure and NF(3) feeding concentration on NF(3) decomposition fraction (eta(NF3)) and energy efficiency E(NF3) were examined in detail. The analytical results demonstrated that the NF(3) was almost completely decomposed (>99%) at input power=30W, [NF(3)](in)=1.0% and eta(NF3) increased with input power. However, adding O(2) to the system inhibited NF(3) decomposition and decreased E(NF3). Moreover, eta(NF3) and E(NF3), decreased with gradually increasing operational pressure. Notably, increasing the NF(3) feeding concentration increased molecule density, reducing eta(NF3), but increasing E(NF3). Furthermore, the products detected in the NF(3)/O(2)/Ar plasma system were NO(2), NO, N(2)O, SiF(4), N(2) and F(2). Potential reaction pathways in the oxygen-based NF(3) plasma environment were built-up and elucidated.     

Biodegradation of triclosan and formation of methyl-triclosan in activated sludge under aerobic conditions

Triclosan is an antimicrobial agent which is widely used in household and personal care products. Widespread use of this compound has led to the elevated concentrations of triclosan in wastewater, wastewater treatment plants (WWTPs) and receiving waters. Removal of triclosan and formation of triclosan-methyl was investigated in activated sludge from a standard activated sludge WWTP equipped with enhanced biological phosphorus removal. The removal was found to occur mainly under aerobic conditions while under anoxic (nitrate reducing) and anaerobic conditions rather low removal rates were determined. In a laboratory-scale activated sludge reactor 75% of the triclosan was removed under aerobic conditions within 150 h, while no removal was observed under anaerobic or anoxic conditions. One percent of the triclosan was converted to triclosan-methyl under aerobic conditions, less under anoxic (nitrate reducing) and none under anaerobic conditions.     

Wastewater characterisation and performance upgrading of a domestic wastewater treatment plant: the Erzincan case

A detailed characterisation of the incoming wastewater and a performance evaluation were carried out for the domestic wastewater treatment plant of Erzincan City. Conventional characterisation results showed that Erzincan has a medium strength wastewater quality. Structural characterisation of the chemical oxygen demand (COD) indicated that the biodegradable fraction of the total COD was 64.7%. The soluble inert fraction was computed as 10.9% of the total COD. In Erzincan, an activated sludge plant provides secondary treatment using Carrousel treatment units. Because some operational problems, such as sludge bulking and foaming, have been experienced, and performance failures related to carbonaceous matter removal have been recorded many times, a new operational strategy suitable for this type of treatment plant was developed. In the new strategy, the sludge age was kept at 22 days, intermittent aeration was abandoned and replaced by continuous aeration, and the sludge recycle ratio was increased to 1.35 from 0.85. The developed operational strategy showed its merit in that previous operational problems largely disappeared and COD concentrations remained below the Turkish discharge limits of 100 mg/l and the NH₄ removal rate was in the range 87–95%.     

铁屑微电解-共沉淀法处理屠宰场废水的研究

利用铁屑微电解-共沉淀法处理屠宰场废水,介绍其作用机理,考察了废水pH值、铁屑用量、反应时间、曝气时间和操作方式等因素对色度和CODCr去除率的影响.结果表明,在废水pH值为4,铁屑用量为15%,常温反应4 h,曝气时间2 h条件下,色度去除率可达100%,CODCr去除率达92.68%.     

超声萃取法处理含油污泥

应用超声强化技术,对以汽油为萃取剂的超声萃取法处理含油污泥的工艺进行了研究,筛选了调整剂、絮凝剂、破乳剂,探讨了萃取温度、萃取时间、超声频率、超声功率等对处理效果的影响。结果表明:在调整剂为采油废水、物料配比为v(萃取剂)∶v(调整剂)∶v(油污泥)=4∶4∶1的条件下,萃取工艺为萃取温度40℃、萃取时间15 min、超声频率40kHz、超声功率150 W时,可回收含油污泥中83.7%的油品。     

Degradation of polycyclic aromatic hydrocarbons (PAHs) in an aged coal tar contaminated soil under in-vessel composting conditions

In-vessel composting of polycyclic aromatic hydrocarbons (PAHs) present in contaminated soil from a manufactured gas plant site was investigated over 98 days using laboratory-scale in-vessel composting reactors. The composting reactors were operated at 18 different operational conditions using a 3-factor factorial design with three temperatures (T, 38 degrees C, 55 degrees C and 70 degrees C), four soil to green waste ratios (S:GW, 0.6:1, 0.7:1, 0.8:1 and 0.9:1 on a dry weight basis) and three moisture contents (MC, 40%, 60% and 80%). PAH losses followed first order kinetics reaching 0.015 day(-1) at optimal operational conditions. A factor analysis of the 18 different operational conditions under investigation indicated that the optimal operational conditions for degradation of PAHs occurred at MC 60%, S:GW 0.8:1 and T 38 degrees C. Thus, it is recommended to maintain operational conditions during in-vessel composting of PAH-solid waste close to these values.     

Kinetics and stoichiometry of aerobic sulfide oxidation in wastewater from sewers-effects of pH and temperature.

Kinetics and stoichiometry of aerobic chemical and biological sulfide oxidation in wastewater from sewer networks were studied. In this respect, the effects of temperature and pH were investigated in the ranges 10 to 20 degrees C and 5 to 9, respectively. The temperature dependency of sulfide oxidation kinetics was described using an Arrhenius relationship. The effect of pH on the rate of chemical sulfide oxidation is related to the dissociation of hydrogen sulfide (H2S) to hydrogen sulfide ion (HS(-)), with HS(-) being more readily oxidized than H2S. Biological sulfide oxidation exhibited the highest rates at ambient wastewater pH, and the reaction was inhibited at both low and high pH values. Chemical sulfide oxidation was found to produce thiosulfate and sulfate, while elemental sulfur was the main product of biological sulfide oxidation. Based on the investigations, general rate equations and stoichiometric constants were determined, enabling the processes to be incorporated to conceptual sewer process models.     

A2/O工艺中的反硝化除磷

A2/O工艺是一种最简单的同步脱氮除磷工艺,但由于其系统中固有的基质竞争和污泥龄等矛盾,在实际应用中特别是处理低C/N比污水时脱氮除磷效率较低.反硝化除磷工艺作为近年来颇受关注的污水生物处理新技术.由于在脱氮除磷过程中可以在碳源利用上耦合,可从一定程度上缓解A2/O工艺中的基质竞争矛盾,使得其在处理低C/N比污水时也能实现较高的脱氮除磷效率.就反硝化除磷的技术原理,结合其在A2/O工艺中的最新研究成果及其控制策略,对A2/O工艺中的反硝化除磷的实现、维持及影响因素进行了分析和探讨,并对其发展方向进行了展望.