二氧化氯和氯复合消毒剂对城市污水的消毒效果

试验研究了二氧化氯和氯复合消毒剂用于经城市污水处理厂处理后的城市污水消毒的效能 ,结果表明 ,二氧化氯和氯复合消毒剂的使用减低了生成的亚氯酸根离子的浓度 ,增加了残余的二氧化氯的浓度 ,粪大肠菌灭活效果良好。     

Emissions of OTNE (Iso-E-super) - mass flows in sewage treatment plants

The fate and mass flows of OTNE ([1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl]ethan-1-one) which is commercialized as Iso-E-Super were studied in three large scale sewage treatment plants (STPs) in detail. The results are compared to 14 smaller ones located in Germany and Switzerland. OTNE inflow concentrations ranged from 4000 to 13,000 ngl(-1) while the effluent concentrations ranged from 500 to 6,900 ngl(-1). It is eliminated from the waste water with 56-64% during waste water treatment. High OTNE concentrations in sewage sludge showed that the elimination was mainly driven by sorption to sludge. This complies with major elimination in the first settling basins (primary settling tanks) while it was removed to a lesser extent in the aeration basin of the activated sludge treatment or in successive biofilters. The mass flows of OTNE in the influent of the German STPs were between 0.9 and 1.9 g per inhabitant and year. In the annual effluents mass flows of OTNE ranged between 0.2 and 0.8 g per inhabitant which complies with data measured in 13 smaller STPs from Switzerland. The similarity of data suggests that the observed mass flow data might be extrapolated to other European regions.     

Pyrolytic characteristics of sewage sludge

In this study, a number of different sewage sludge including sludge samples from industrial and hospital wastewater treatment plants were characterized for pyrolysis behavior by means of thermogravimetric analysis up to 800 degrees C. According to the thermogravimetric results, five different types of mass loss behaviors were observed depending on the nature of the sludge used. Typical main decomposition steps occurred between 250 and 550 degrees C although some still decomposed at higher temperatures. The first group (Types I, II and III) was identified by main decomposition at approximately 300 degrees C and possible second reaction at higher temperature. Differences in the behavior may be due to different components in the sludge both quantitatively and qualitatively. The second group (Types IV and V), which rarely found, has unusual properties. DTG peaks were found at 293, 388 and 481 degrees C for Type IV and 255 and 397 degrees C for Type V. Kinetics of sludge decomposition can be described by either pseudo single or multicomponent overall models (PSOM or PMOM). The activation energy of the first reaction, corresponding to the main pyrolysis typically at 300 degrees C, was rather constant (between 68 and 77 kJ mol(-1)) while those of second and third reactions were varied in the range of 85-185 kJ mol(-1). The typical order of pyrolysis reaction was in the range of 1.1-2.1. The pyrolysis gases were composed of both saturated and unsaturated light hydrocarbons, carbon dioxide, ethanol and chloromethane. Most products, however, evolve at a quite similar temperature regardless of the sludge type.     

The arrival and discharge of conjugated estrogens from a range of different sewage treatment plants in the UK

The occurrence of free and conjugated estrogens was examined in a survey of eleven sewage treatment plants (STPs) and their discharge water in the United Kingdom using grab sampling. The STPs included trickling filter with and without tertiary treatment, and activated sludge with tertiary treatment. For three activated sludge plants both influent and effluent samples were compared. For a further 8 STPs only the effluent was examined. The estrone-3-sulphate, estradiol-3-sulphate and estriol-3-sulphate concentrations (up to 20 ng L⁻¹) were typically 5-fold that of the respective free estrogen concentration in the effluents. This represents a substantial additional ‘potential’ estrogen load arriving in the receiving waters. Estrone-3-glucuronide was found at 9 ng L⁻¹, estradiol-3-glucuronide at 7 ng L⁻¹, and estriol-3-glucuronide at 32 ng L⁻¹ in sewage influent. Except on one occasion, no glucuronide conjugates could be found in the effluent. The results suggest in most cases glucuronide conjugates will be completely transformed in sewage treatment whilst sulphate conjugates will only be partially removed.     

Levels and distribution patterns of short chain chlorinated paraffins in sewage sludge of wastewater treatment plants in China

Short chain chlorinated paraffins (SCCPs) are listed as persistent organic pollutant candidates in the Stockholm Convention and are receiving more and more attentions worldwide. In general, concentrations of contaminants in sewage sludge can give an important indication on their pollution levels at a local/regional basis. In this study, SCCPs were investigated in sewage sludge samples collected from 52 wastewater treatment plants in China. Concentrations of total SCCPs (ΣSCCPs) in sludge were in the range of 0.80-52.7 μg/g dry weight (dw), with a mean value of 10.7 μg/g dw. Most of SCCPs in the sludge samples showed a similar congener distribution patterns, and C(11) and Cl(7,8) were identified as the dominant carbon and chlorine congener groups. Significant linear relationships were found among different SCCP congener groups (r(2) ≥ 0.9). High concentrations of SCCPs in sewage sludge imply that SCCPs are widely present in China.     

Laboratory evaluations of the thermal degradation properties of toxic organic materials in sewage sludge

Laboratory thermal decomposition studies were performed to evaluate potential emissions from sewage sludge incinerators. Precisely controlled thermal decomposition experiments were conducted on sludge spiked with mixtures of hazardous organic compounds, on mixtures of pure compounds without sludge, and on unspiked sludge. Experiments were conducted in nitrogen and air atmospheres with gas phase reaction times of 2.0 seconds over the temperature range 300 degrees C-1000 degrees C. It was found that sludge inhibited the decomposition of moderately stable spiked contaminants but accelerated the decomposition of the most stable components. This effect was attributed to radical scavengers produced by the sludge matrix at lower temperatures which then decomposed at higher temperatures. A multiple hearth simulation study suggested that most of the organic material present in the sludge matrix is vaporized within the upper hearths that are held at lower temperatures and may consequently escape from such incinerators undestroyed. A number of stable byproducts resulted from the sludge decomposition that may be of environmental concern.     

Estimation of faecal pollution based on the amounts of urobilins in urban rivers

An attempt was made to establish a new indicator for faecal pollution in aquatic environments using a sensitive determination method for urobilins, which are only present in mammalian faeces and urine. Assessment of urobilin stability was followed by determination of the amount of urobilins in river water. When river water containing urobilins was shaken at room temperature, the number of total and faecal coliforms increased, while urobilins decreased only in small amounts, indicating that urobilin is relatively stable in river water and hence can serve as a useful indicator for the estimation of faecal pollution of river water. The amount of urobilins in the river waters increased steeply from the mid-point of a stream near a sewage treatment plant, while amounts in the upper stream were very low. The amount of urobilins in river water increased after rainfall. Findings suggested that urobilin, i.e. sewage, originated from the output of the sewage treatment plant and raw sewage.     

Laboratory Evaluations of the Thermal Degradation Properties of Toxic Organic Materials in Sewage Sludge

Laboratory thermal decomposition studies were performed to evaluate potential emissions from sewage sludge incinerators. Precisely controlled thermal decomposition experiments were conducted on sludge spiked with mixtures of hazardous organic compounds, on mixtures of pure compounds without sludge, and on unspiked sludge. Experiments were conducted in nitrogen and air atmospheres with gas phase reaction times of 2.0 seconds over the temperature range 300°C-1000°C.

It was found that sludge inhibited the decomposition of moderately stable spiked contaminants but accelerated the decomposition of the most stable components. This effect was attributed to radical scavengers produced by the sludge matrix at lower temperatures which then decomposed at higher temperatures. A multiple hearth simulation study suggested that most of the organic material present In the sludge matrix is vaporized within the upper hearths that are held at lower temperatures and may consequently escape from such incinerators undestroyed. A number of stable byproducts resulted from the sludge decomposition that may be of environmental concern.     

Persistent organic chemicals in sewage effluents: I. Identifications of nonylphenols and nonylphenolethoxylates by glass capillary gas chromatography / mass spectrometry

Nonylphenols and nonylphenolethoxylates with one, two, and three oxyethylene groups were identified in effluents from activated sludge sewage treatment plants. The complex mixtures of isomers are considered to be refractory metabolites of nonionic detergents.     

The fate of linear alcohol ethoxylates during activated sludge sewage treatment

Model continuous activated sludge (CAS) plants (Husmann units) were used to study the fate of two commercial, alcohol ethoxylate (AE) surfactants during aerobic sewage treatment. The surfactants were produced by the ethoxylation of an essentially linear C(12-15) alcohol (NEODOL 25) with an average of 7 (C(12-15)EO7) or 3 (C(12-15)EO3) moles of ethylene oxide (EO). Recent analytical developments made it possible to measure levels of AE that included the free alcohol and EO1 oligomers across the CAS system, from the influent feed, on the activated sludge, through to the effluent. Measured concentrations of AE (as C(12-15)EO(0-20)) in the synthetic sewage feeds to the test CAS plants lay in the range 11-13 mg/l. During stable operation at 20 degrees C, an average of 5 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal (bioelimination) of >99.9%. When levels of AE on the sludge, and polyethylene glycols (PEGs--an expected biodegradation intermediate) in the effluent and on the sludge were also taken into account, biodegradation was considered to be responsible for >98.7% of the observed removal. During operation at a winter temperature (10 degrees C), an average of 26 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal of 99.8%. Biodegradation was estimated to be responsible for >97.2% of the observed removal. During operation at 20 degrees C, an average of 7 microg/l AE were present in the C(12-15)EO3 CAS plant effluent, giving a removal of >99.9%. No analysis for PEG was performed in this case but the low level of AE on the sludge (0.2 mg/g dry solids) suggested that biodegradation was responsible for most of the observed removal. Neither surfactant had any adverse effect on the sewage treatment efficiencies of the CAS plants in terms of dissolved organic carbon (DOC) removal, nitrification or biomass levels.     

Determination of detoxification to Daphnia magna of four pharmaceuticals and seven surfactants by activated sludge

Pharmaceuticals are bioactive compounds generally resistant to biodegradation, which can make them problematic when they are released into nature. The use pattern for pharmaceuticals means that they are discharged into water via sewage treatment plants. Also surfactants are discharged through sewage treatment plants, primarily due to their use in detergents and shampoos and other cleaners. In this study the acute toxicity to Daphnia magna of four pharmaceuticals (ciprofloxacin, ibuprofen, paracetamol and zinc pyrithione) and seven surfactants (C8 alkyl glucoside, C6 alkyl glucoside, sodium caprylimidiopropionate, tallow-trimethyl-ammonium chloride, potassium decylphosphate, propylheptanol ethoxylate and alkylmonoethanolamide ethoxylate) was determined. Abiotic (without activated sludge bacteria) and biotic (with activated sludge bacteria) detoxification was also determined. The 24-h EC50s ranged from 2 μg L(-1) for the most toxic substance (zinc pyrithione) to 2 g L(-1) for the least toxic compound (C6 alkyl glucoside). Detoxification rates determined as the ratio between initial EC50 and EC50 after 1 week in water with activated sludge bacteria ranged from 0.4 (paracetamol) to 13 (zinc pyrithione). For most of these chemicals detoxification rate decreased after 1 week, but for one (alkylmonoethanolamide ethoxylate) it increased from about 2 to 30 times after 2 weeks. Many of these chemicals were "detoxified" also abiotically at about the same rate as biotically. Further studies are needed to determine the degradation products that were precipitated (aggregated) for some of the tested chemicals. Altogether, this study has shown that there are large differences in toxicity among chemicals entering sewage treatment plants, but also that the detoxification of them can differ. Therefore, the detoxification should receive more attention in the hazard and risk assessment of chemicals entering sewage treatment plants.     

Removal of DEHP in composting and aeration of sewage sludge

The potential of composting and aeration to remove bis(2-ethylhexyl) phthalate (DEHP) from municipal sewage sludge was studied with two dewatered sludges: raw sludge and anaerobically digested sludge. Composting removed 58% of the DEHP content of the raw sludge and 34% of that of the anaerobically digested sludge during 85 days stabilisation in compost bins. A similar removal for the anaerobically digested sludge was achieved in a rotary drum in 28 days. Less than 1% of DEHP was removed with the compost leachate. Although DEHP removal was greater from raw sludge compost than anaerobically digested sludge compost, the total and volatile solids removals were on the same level in the two composts. In the aeration of raw sludge at 20 degrees C the DEHP removals were 33-41% and 50-62% in 7 and 28 days, respectively. Both composting and aeration are concluded to have the potential to reduce the DEHP contents typically found in sewage sludges to levels acceptable for agricultural use.     

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.     

污泥浓度对微孔曝气氧传质过程的影响

污泥浓度是影响微孔曝气氧传质过程的重要因素之一。在小试及中试规模上，研究了不同污泥浓度对微孔曝气氧传质过程的影响，得出曝气性能随污泥浓度的变化规律。结果表明，当污泥浓度低于2000mg／L时，曝气性能随浓度的增大而增强，在2000～3000mg／L时，KLa达到最大值；当污泥浓度大于2000～3000mg／L时，曝气性能随污泥浓度增大而降低，当污泥浓度大于5000mg／L时，曝气性能急剧降低。这一规律对于在设计和运行中合理确定污水处理中的污泥浓度，在达到处理效果的前提下，尽量降低电耗具有重要意义。     

Formation of organochlorine compounds in kraft pulp bleaching processes

The most abundant volatile organochlorine compounds (VOCCs), trichloroacetic and dichloroacetic acids and AOX, were determined in bleaching effluent and waste water from three kraft pulp mills during ClO₂ bleaching. 0.6–7.7 g of VOCCs per ton bleached pulp were formed, the most abundant being chloroform and dichloroacetic acid methyl ester. Most of the VOCCs were removed during treatment, and it was estimated that 2–30 t of VOCCs would be removed annually from activated sludge treatment plants in Finnish kraft pulp mills using elemental chlorine free bleaching, most likely by volatilization. Dichloroacetic acid was formed in considerably higher amounts than trichloroacetic acid, and both compounds were removed effectively during treatment. The formation of all organochlorine compounds decreased considerably when non-chlorinated bleaching was employed.     

Persistence of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge-amended soil

The application of sewage sludge as a fertilizer is a common method used to improve soil properties. However, sewage sludge may contain various organic pollutants including polycyclic aromatic hydrocarbons. In the present study, the persistence of PAHs in soils fertilized with different sewage sludge doses was compared in relation to the sewage sludge dose applied (30, 75, 150, 300 and 600 Mgha(-1)) and the content of the polycyclic aromatic hydrocarbons in them. The experiment was carried out in two blocks of experimental plots divided according to the type of plants grown: field plants and perennial-willow. Sewage sludge addition to soils resulted in an increase in the content of polycyclic aromatic hydrocarbons in these soils. This increase was proportional to the quantity of sewage sludge applied. The results obtained showed that during a 42/54-month period, more than half of the individual PAHs introduced into the soil with sewage sludge were degraded. The scope of dissipation depended on the sewage sludge dose and the use to which the area was put. In the experiment with the willow only in the case of the highest sludge dose was a decrease in the PAH content above 50% noted; whereas in the case of the experiment with the field plants, it was higher by 50% for all sewage sludge doses. In experiment with field plants the highest scope of individual PAH disappearance was observed in the soil with the sewage sludge dose amounting to 300 Mgha(-1). In experiment with willow a relatively high dissipation of individual PAHs (>50%) was found in the treatment with the highest sludge dose (600 Mgha(-1)). A wider PAH dissipation range in the experiment with field plants was conditioned by the more favourable conditions created as a result of the breeding treatments applied. Agrotechnical treatments clearly increased the disappearance of the PAHs in those soils fertilized with the lowest sewage sludge doses (30 and 75 Mgha(-1)). The results obtained showed that the preferred method of treating a light soil fertilised with sewage sludges should be a one-year system, with a sludge application of 75 Mgha(-1).     

Effects of chlorination on the adhesion strength and deflocculation of activated sludge flocs.

A side effect of the application of chlorine for controlling filamentous bulking is deflocculation of floc-forming bacteria, which may cause unacceptable effluent deterioration depending on dosing. It was assumed that chlorine may adversely affect the adhesion ability of floc bacteria, promoting their erosion in shear flow. The effect of chlorination on the strength of activated sludge flocs was investigated. The adhesion-erosion (AE) model developed by Mikkelsen and Keiding was used to interpret results from deflocculation tests with varying shear and solids concentration. The AE model yields the adhesion enthalpy (deltaHG/R) of cells in sludge flocs and parameters from the model were used to quantify the sludge in terms of floc strength. Two activated sludges with different initial characteristics were studied. The resulting model parameters showed that the AE model was suitable for quantifying the bond energy of particles to the activated sludge exposed to chlorine. For one activated sludge, adhesion of cells was largely unaffected by the applied chlorine doses. A second sludge showed reduced adhesion strength with chlorine, leading to increasing deflocculation. The simple batch test and AE model proved valuable for assessing the effect of chlorination on the flocs in activated sludge. By use of these procedures, it is possible to determine acceptable chlorine dosing to avoid excessive deflocculation and effluent deterioration.     

Removal and formation of chlorinated triclosan derivatives in wastewater treatment plants using chlorine and UV disinfection

Triclosan, a common antimicrobial agent, may react during the disinfection of wastewater with free chlorine to form three chlorinated triclosan derivatives (CTDs). This is of concern because the CTDs may be photochemically transformed to tri- and tetra-chlorinated dibenzo-p-dioxins when discharged into natural waters. In this study, wastewater influent, secondary (pre-disinfection) effluent, and final (post-disinfection) effluent samples were collected on two occasions each from two activated sludge wastewater treatment plants, one using chlorine disinfection and one using UV disinfection. Concentrations of triclosan and three CTDs were determined using ultra performance liquid chromatography-triple quadrupole mass spectrometry with isotope dilution methodology. Triclosan and the CTDs were detected in every influent sample at levels ranging from 453 to 4530 and 2 to 98 ng L⁻¹, respectively, though both were efficiently removed from the liquid phase during activated sludge treatment. Triclosan concentrations in the pre-disinfection effluent ranged from 36 to 212 ng L⁻¹, while CTD concentrations were below the limit of quantification (1 ng L⁻¹) for most samples. In the treatment plant that used chlorine disinfection, triclosan concentrations decreased while CTDs were formed during chlorination, as evidenced by CTD levels as high as 22 ng L⁻¹ in the final effluent. No CTDs were detected in the final effluent of the treatment plant that used UV disinfection. The total CTD concentration in the final effluent of the chlorinating treatment plant reached nearly one third of the triclosan concentration, demonstrating that the chlorine disinfection step played a substantial role in the fate of triclosan in this system.     

Potential of recycling gamma-irradiated sewage sludge for use as a fertilizer: a study on chickpea (Cicer arietinum)

The effects of gamma-irradiated sludge on the growth and yield of chickpea (Cicer arietinum) in pot cultures have been studied. Compared to plants grown only in soil, root length, fresh weight and dry weight of plants grown in soil supplemented with unirradiated sludge were found to be significantly reduced. This inhibition in growth was found to be nullified when plants were grown in soil supplemented with gamma-irradiated sludge, suggesting that gamma radiation induced inactivation of toxic substance(s) in sludge. The protein content of plants grown in soil supplemented with irradiated sludge was also found to be significantly increased compared to those grown with unirradiated or no sludge, after 45 days. There was no significant effect of gamma irradiated sludge on shoot length, total soluble sugars, starch content and yield of chickpea plants. The results obtained suggest that the sludge tested, and obtained from the digester of a conventional domestic sewage treatment plant, is inhibitory to several growth parameters. Gamma irradiation of sewage resulted in removal of this inhibition. This suggests a possibility of beneficial and safe recycling of gamma-irradiated sludge for agricultural uses.     

曝气强度对城市污泥重金属生物沥滤过程的影响研究

以氧化亚铁作为底物，氧化亚铁硫杆菌（Thiobacillusferrooxidans）为主要沥滤微生物，在底物投配比为10 g/L，温度为25℃，污泥浓度为123g/L的条件下，采用5种不同曝气强度对桂林城市污泥中重金属进行生物沥滤试验。结果表明，生物沥滤的经济曝气强度宜控制在每升污泥0.4L/（min·L），沥滤3 d后，污泥中超标元素Cu、Zn和Cd的去除率分别达到62.53%、67.80%和54.63%，沥滤处理后污泥中残余重金属含量符合污泥农用的国家标准。