The potential for recycling municipal sewage sludge as a substrate for wetland creation

Municipal sewage sludge (MSS) is proposed as a suitable substrate for wetland creation. Sludge disposal is currently limited to terrestrial conditions due to concern for the transmission of pollutants. Wetland structure and wetland biogeochemical cycles were compared with sludge disposal practices to identify strengths and weaknesses in wetland mechanisms for pollution control. Potential pollution from sludge use is proposed to be mitigated both by wetland function and by the substrate construction method. Because MSS requires specific handling techniques to prevent undesired release into the environment, to protect workers and to be practical for construction, designs responsive to the nature of the construction material were necessary. Three designs were developed, evaluated and compared in terms of aesthetics, educational opportunities, environmental safety, nutrient cycling, waste material utilization, substrate construction requirements and wetland establishment requirements.     

城市污水厂污泥制备陶粒的试验研究

1 引言 随着城市污水处理厂的规模不断扩大,处理程度不断提高,剩余污泥的排放量越来越大.如何合理处置污泥,解决污泥的出路已成为非常紧迫的任务.目前国内外污泥处理处置的主要方式有填埋、焚烧、堆肥等方法.     

污泥陶粒次轻混凝土的制备与性能研究

用碎石和污泥陶粒作为混合粗集料配制了不同集料组成的次轻混凝土试样,系统地研究了它们的力学性能和热学性能。虽然污泥陶粒本身强度不高,但在粗集料中掺入适量污泥陶粒(占粗集料的体积分数x=25%)所制备的次轻混凝土,其早期强度与不掺污泥陶粒的混凝土试样相当。上述现象归结于污泥陶粒与水泥石界面较为致密的组织结构,当其取代碎石集料后,减少了集料与水泥石界面的疏松组织结构,使集料与水泥石界面区的微观结构得到增强。污泥陶粒次轻混凝土的弹性模量介于普通集料混凝土和轻集料混凝土之间,具有比同强度等级普通混凝土更好的延展性,和比轻集料混凝土更高的强度与抗变形能力。与普通混凝土(x=0)相比,当次轻混凝土中x=25%时,其导热系数可降低46%,即掺入少量污泥陶粒可明显提高混凝土的保温隔热性能。     

提高污泥浓度对市政污水处理的影响研究

综合分析了MLVSS的变化与MLSS之间的关系,以及COD,SS,氨氮的去除与MLSS的关系,并以某县城的污水处理厂为例,探讨了污泥浓度的变化情况,同时对浓度提高的污泥进行试验,结果表明:当MLSS不超过6 000 mg/L时,坚持正常的排泥较为合适。     

Resuspension of coal and coal/municipal sewage sludge combustion generated fine particles for inhalation health effects studies

Airborne particulate matter (PM) is an important environmental issue because of its association with acute respiratory distress in humans, although the specific particle characteristics that cause lung damage have yet to be identified. Particle size, acid aerosols, water-soluble transition metals (e.g. Cu, Fe, V, Ni and Zn), polyaromatic hydrocarbons, and particle composition are the focus of several popular hypotheses addressing respiratory distress. All of the above mentioned characteristics are contained in PM generated from the combustion of both pulverized coal, and biomass, including dried municipal sewage sludge (MSS). In this investigation, we report results from collaborative interdisciplinary research on the inhalation health risks caused by particles emitted from the co-combustion of municipal sewage sludge (MSS) and coal. A solid particle resuspension system was implemented to resuspend ash particles. Mice were exposed to resuspended coal and MSS/coal ash particles. Mice exposed to MSS/coal ash particulate demonstrated significant increases in lung permeability, a marker of the early stages of pathological lung injury, while the mice exposed to coal-only ash did not. These results show that the composition of particles actually inhaled is important in determining lung damage. Zinc was significantly more concentrated in the MSS/coal ash than coal ash particles and the pH of these particles did not differ significantly. Specifically, an MSS/coal mixture, when burned, emits particles that may cause significantly more lung damage than coal alone, and that consequently, the use of MSS as a 'green', CO2-neutral replacement fuel should be carefully considered.     

城市生活污泥生产陶粒的研究与实践

城市污泥的资源化利用是污泥较深度、较彻底处置的一种有效途径,是绿色、节能、环保循环经济发展的方向。通过试验和生产实践研究,利用城市生活污泥和淤泥生产新型节能建筑轻集料——陶粒,不仅能生产密度等级为500~700㎏/m3的普通陶粒,还可生产<500㎏/m3的超轻陶粒,其性能良好,质量优良。     

Advanced sewage treatment process with excess sludge reduction and phosphorus recovery

An advanced sewage treatment process has been developed, in which excess sludge reduction by ozonation and phosphorus recovery by crystallization process are incorporated to a conventional anaerobic/oxic (A/O) phosphorus removal process. The mathematical model was developed to describe the mass balance principal at a steady state of this process. Sludge ozonation experiments were carried out to investigate solubilization characteristics of sludge and change in microbial activity by using sludge cultured with feed of synthetic sewage under A/O process. Phosphorus was solubilized by ozonation as well as organics, and acid-hydrolyzable phosphorus (AHP) was the most part of solubilized phosphorus for phosphorus accumulating organisms (PAOs) containing sludge. At solubilization of 30%, around 70% of sludge was inactivated by ozonation. The results based on these studies indicated that the proposed process configuration has potential to reduce the excess sludge production as well as to recover phosphorus in usable forms. The system performance results show that this system is practical, in which 30% of solubilization degree was achieved by ozonation. In this study, 30% of solubilization was achieved at 30 mgO(3)/gSS of ozone consumption.     

UASB-BAF处理城市污水的试验研究

介绍了采用UASB-BAF组合反应器的组合工艺，研究了反应器在正常pH值、温度条件下的工作特性，并分析了试验结果，为城市污水及工业废水的处理提供了依据。     

Optimization of single and mixed cultures for solid state fermentation of municipal sewage sludge

Trichoderma harzianum (Th), Phanerochaete chrysosporium ATCC 24725 (Pc) and Mucor hiemalis (Mh) isolated from three sources: wastewater; sewage sludge; and sludge cake were selected for use as compatible/incompatible single and mixed cultures in the treatment of municipal sewage sludge. Five experiments were carried out using (Pc), (Th), a mixture of (Pc/Th), (Mh) and a mixture of (Pc/Mh), in addition to a control where no micro‐organism was used. The experiments were used to evaluate their potential performance as compatible/incompatible single and mixed cultures for the treatment of municipal wastewater sewage sludge from treatment plants using solid state fermentation technique (SSF). The results showed that the best micro‐organism for composting was found to be (Th) and a mixture of (Pc/Th), while (Pc/Mh) was incompatible culture. The C/N ratio for Th changed from 8.46 to 17.8 at the end of the process, (Ph/Th) increased from 7.21 to 15.9, while (Pc/Mh) increased from 8.49 to 29. The pH value also affected by the fungal cultures which was also changed for (Th) from 4.29 to 6.8, for (Pc/Th) was changed from 7.27 to 6.7 and for (Pc/Mh) was changed from 6.6 to 5.3. Effective results were observed by using mixed culture after 19–21 days compared to other single treatments after 24–32 days.     

Fate of natural estrogens in batch mixing experiments using municipal sewage and activated sludge

Since natural estrogens such as 17beta-estradiol (E2) and estrone (E1) are excreted daily by humans, E2 and E1, which are classified as inevitable endocrine-disrupting chemicals, are always present in sewage wastewater. For several years, the monitoring and removal of natural estrogens at sewage treatment plants have been examined by many investigators. However, little is known regarding the exact behavior of estrogens in actual sewage when in contact with activated sludge. In this study, the fate of E2 and E1 as a result of adsorption and decomposition in batch mixing experiments using municipal wastewater and activated sludge collected from an actual municipal sewage treatment plant was investigated. Estrogen concentrations were determined using an enzyme-linked immunosorbent assay (ELISA) kit. E2 and E1 in sewage were removed from the liquid phase in contact with activated sludge, and E2 and E1 adsorbed on the sludge were decomposed in 4h. Significant changes in the adsorption and decomposition of E2 and E1 on the sludge were not observed at low temperatures or when different sludge samples were used such as those acclimatized to low-loading and high-loading conditions. In contrast, the processes leading to the removal of estrogens, such as the adsorption and decomposition of estrogens in contact with activated sludge, were inactivated by sterilizing the sludge. Natural estrogens adsorb onto the activated sludge, and are therefore easy to be biodegraded. In a biological reaction process, therefore, the estrogens will be rapidly removed at the initial stage, when the sewage is satisfactorily mixed with the sludge.     

The thickening and treatment of sewage sludges to minimize phosphorus release

The Johannesburg City Council has operated biological and chemical nutrient removal wastewater treatment plants for the past 15–16 years. With the advent of more sophisticated sludge handling techniques, problems have been experienced with the recycle of phosphorus-rich sludge processing liquors to the liquid phase. These problems are expected to increase in the future. This paper describes laboratory and pilot scale experiments to determine viable methods for phosphorus removal from sludge liquors and ways of obviating phosphorus release from phosphorus-rich activated sludges. The design of new full-scale plants being constructed to pretreat phosphorus-rich sludges prior to dewatering are also discussed. The paper also describes innovative process layouts for sludge treatment keeping in mind various options for final sludge disposal. Emphasis is placed on the pre-aeration and phosphate precipitation from anaerobically digested and raw primary sludges and techniques for the thickening and dewatering of primary and waste activated sludges to minimize phosphate release into the liquors so produced. The technique of sludge thickening on linear screens is described and the coupling of linear screens to belt presses to complete the dewatering operation.     

复合式MBR处理城市污水的试验研究

阐述了复合式MBR处理城市污水的流程与方法,考察了复合式MBR对城市污水中有机污染物、氨氮、悬浮颗粒物的处理效果,对复合式MBR的处理效率进行了分析,结果表明,该工艺很好的满足了城市污水处理回用的要求。     

Per capita phosphorus loading from domestic sewage

To assess the phosphorus contribution from domestic sewage to Lough Neagh, Northern Ireland, daily per capita loadings were measured by monitoring the effluent from a housing estate. A modern estate with 472 houses was chosen because it was free from industry and had separate foul and storm drainage systems. By a house-to-house census the total population was found to be 1645. Daily loadings in the foul sewer were calculated from measured hourly flow rates and concentration data. The effective population contributing to the foul sewer was estimated by making allowances for export from or import to the estate of excrement by workers and school-children. An attempt was made to verify the assumptions used in estimating the effective population by monitoring the loading in the foul sewer of creatinine, a metabolic end-product excreted in constant amounts in urine. Predicted creatinine loadings, using population data and per capita excretion values, were in good agreement with measured loadings. Per capita daily loadings of soluble orthophosphate, total soluble phosphorus, total phosphorus and BOD were calculated using the effective population and measured loadings for Mondays to Fridays during three weekly survey periods. The results indicated a per capita value of 1.8 g day⁻¹ for total phosphorus in domestic sewage.     

Antimicrobial resistance in Enterococcus spp. isolated in inflow, effluent and sludge from municipal sewage water treatment plants

Antimicrobial resistance of enterococci was investigated in 42 samples of crude inflow, treated effluent and sludge collected in 14 municipal sewage treatment plants of Portugal. A total of 983 enterococci were recovered and tested, using the diffusion agar method, regarding their sensitivity to 10 different antimicrobial drugs. Multidrug resistance was present in 49.4% of the isolates. Only 3.3% and 0.6% of the investigated strains were resistant to ampicillin and vancomycin, respectively. Resistances found against rifampicin (51.5%), tetracycline (34.6%), erythromycin (24.8%) and nitrofurantoin (22.5%), are causes for substantial concern. Almost 14% of isolates were resistant to ciprofloxacin. Wastewater treatment resulted in enterococci decrease between 0.5 and 4log; nevertheless, more than 4.4 x 10(5)CFU/100ml were present in the outflow of the plants. Our data indicate that the use of antimicrobials had created a large pool of resistance genes and that sewage treatment processes are unable to avoid the dissemination of resistant enterococci into the environment.     

Kinetic competition between phosphorus release and denitrification on sludge under anoxic condition

The kinetic behaviors of simultaneous phosphorus release and denitrification on sludge were investigated under anoxic condition. A phosphorus enriched sludge produced from Anaerobic-Anoxic-Oxic (AnAO) process under various SRT (5, 10 and 15 days) operation conditions was carried out in a series of batch tests. Experimental results indicated that the available organic substrate determined the kinetic behaviors of phosphorus release/uptake and denitrification. The simultaneous phosphorus release and denitrification demonstrated a kinetic competition under anoxic conditions in the presence of an available organic substrate. When the substrate was abundant, sludge was under “releasable-phosphorus-limited” condition; phosphorus release rate decreased slightly by nitrate inhibition. However, nitrate significantly inhibited phosphorus release when sludge was under “initial-substrate-limited” condition. Moreover, the sludge's phosphorus contents (as created by different SRT processes) dominated the kinetics of competition between phosphorus release and denitrification. The sludge with a high phosphorus content had a higher phosphorus release rate in accordance with a lower denitrification rate. Additionally, the substrate sequestrated rate markedly increased under the condition of simultaneous phosphorus release and denitrification. Finally, a preliminary metabolism model of denitrifying phosphorus removal bacteria was proposed, and found to be capable of adequately accounting for simultaneous phosphorus release and denitrification under anoxic conditions.     

On wet chemical phosphorus recovery from sewage sludge ash by acidic or alkaline leaching and an optimized combination of both

The advantages and drawbacks of existing wet chemical phosphorus (P) recovery technologies, their applicability to different types of sewage sludge ash (SSA) and the role of the decay products of detergent zeolites as a source of reactive Al in SSA are analyzed. Since neither a purely acidic nor a purely alkaline treatment are able to provide satisfactory technical solutions a wet chemical phosphorus (P) recovery process for sewage sludge ashes (SSAs) is investigated in detail that is based on a sequential treatment of SSA with an acid and a base. As a result of an acidic pre-treatment, the P fraction of the raw SSA that was bound as - alkaline-insoluble - calcium phosphate (Ca-P) is converted into aluminum phosphate (Al-P). This newly formed Al-P can be easily dissolved via alkaline treatment and then easily separated from the alkaline leachate via precipitation of Ca-P. The Al-component can be reused as precipitant for P-removal in waste water treatment plants (WWTPs). The investigated process requires fewer chemicals than the direct acidic dissolution of all P-compounds contained in the SSA. This is due to the described rearrangement of the P component from Ca-P to Al-P. That such a rearrangement of P occurs indeed was confirmed through a combination of XRD, ICP and XRF analyses together with mass balance calculations. The present investigation proves that the process works for very different types of SSAs: For Al-rich SSAs that come from WWTPs where Al-salt is used for chemical P-removal the described sequential treatment process works best and yields P-recovery rates as high as 70-77%. But even for SSAs from WWTPs where only iron salt is used for chemical P-removal, a considerable amount of the reactive Al necessary for the described P-rearrangement is supplied by decay products of detergent zeolites, a hidden Al-source present in most SSAs produced in Europe.     

Aerial organic chemical release from activated sludge

The objective of this study was to investigate some of the potentially controlling factors influencing the atmospheric release of volatile organic compounds from the activated-sludge sewage treatment process. A bench-scale aeration vessel was used to investigate the influence of aeration rate, suspended solids concentration and detergent concentration on the rate of stripping of hexa-chlorobicycloheptadiene (Hex-BCH) and chloroform from simulated wastewater. These compounds had previously been found to be released from an 80 mgd activated sludge wastewater treatment plant.First order kinetic decay was found for the stripping of Hex-BCH and chloroform. The influences of aeration rate, suspended solids concentration and detergent concentration on the release of Hex-BCH were each statistically significant. The increase in aeration rate appreciably enhanced the release of Hex-BCH, while increasing the concentration of suspended solids inhibited stripping. A linear relationship was found between detergent concentration and stripping rate. Aeration rate was the only significant variable influencing the release of chloroform. The results suggest that Hex-BCH is stripped from an adsorbed state and chloroform from a dissolved state.     

Behaviour and occurrence of estrogens in municipal sewage treatment plants--II. Aerobic batch experiments with activated sludge

Aerobic batch experiments containing a diluted slurry of activated sludge from a real sewage treatment plant (STP) near Frankfurt/Main were undertaken, in order to investigate the persistence of natural estrogens and contraceptives under aerobic conditions. The batch experiments showed that while in contact with activated sludge the natural estrogen 17 beta-estradiol was oxidized to estrone, which was further eliminated in the batch experiments in an approximate linear time dependence. Further degradation products of estrone were not observed. 16 alpha-hydroxyestrone was rapidly eliminated, again without detection of further degradation products. The contraceptive 17 alpha-ethinylestradiol was principally persistent under the selected aerobic conditions, whereas mestranol was rapidly eliminated and small portions of 17 alpha-ethinylestradiol were formed by demethylation. Additionally, two glucuronides of 17 beta-estradiol (17 beta-estradiol-17-glucuronide and 17 beta-estradiol-3-glucuronide) were cleaved in contact with the diluted activated sludge solution and thus 17 beta-estradiol was released. The glucuronidase activity of the activated sludge was further confirmed by the cleavage of 4-methylumbelliferyl-beta-D-glucuronide (MUF-beta-glucuronide) in a solution of a activated sludge slurry and Milli-Q-water (1:100, v/v). The turnover rate obtained was approximately steady state, with a turnover rate of 0.1 mumol/l for the released MUF. Hence, it is very likely that the glucuronic acid moiety of 17 beta-estradiol glucuronides and other estrogen glucuronides become cleaved in a real municipal STP, so that the concentrations of the free estrogens increase.     

Laboratory studies of virus survival during aerobic and anaerobic digestion of sewage sludge

The survival of three enteroviruses (polio 1, coxsackie B3 and echo 1) and a rotavirus (SA-11) was studied under laboratory conditions. The effects of temperature, dissolved oxygen, detention time, sludge source and virus type on virus inactivation were determined. Temperature was the single most important factor influencing the rate of virus inactivation. No significant differences were found for virus inactivation rates at dissolved oxygen levels between 0.9 and 5.8 mg/l. However, the inactivation rate of the viruses under aerobic conditions was found to be significantly greater than the inactivation rate under anaerobic conditions (−0.77log₁₀/day vs −0.33 log₁₀/day). Sludge source, detention time and virus type did not significantly influence the rate of virus inactivation.     

Bacterial pathogen incidences in sludge from Swedish sewage treatment plants

This study surveyed the presence of bacterial pathogens in eight Swedish sewage treatment plants (STPs), with four different treatment methods, focusing on detection of zoonotic bacteria in raw and treated sludge. Salmonella spp., Listeria monocytogenes, Campylobacter coli and jejuni, Escherichia coli O157 and indicator bacteria were investigated. Samplings were performed from July 2000 to June 2002, resulting in 64 raw sludge samples and 69 treated sludge samples. The samples from raw sludge (67%) and treated sludge (55%) were positive for Salmonella; 49 different serotypes were detected. Restriction enzyme analysis and pulsed field gel electrophoresis of Salmonella serotypes indicated that Salmonella persists in STPs and that there is a continuous supply of new strains. There are differences in treatment methods concerning the reduction of pathogens and indicator bacteria. If spread on arable land, sludge increases the environmental load of pathogens; this increases the risk for spreading diseases to people and animals.