Variation among plant species in pollutant removal from stormwater in biofiltration systems

Biofiltration systems use vegetation to improve efficiency of pollutant removal from stormwater, but little is known of how plants vary in their capacity to improve biofilter effectiveness. We used a pot trial of 20 Australian species to investigate how species vary in the removal of pollutants from semisynthetic storm water passing through a soil filter medium. Effluent levels of total suspended solids (TSS), Al, Cr, Cu, Pb and Zn were similarly low for vegetated and non-vegetated soils, with reduction to <1-12% of levels in the stormwater input. N and P effluent concentrations were generally lower from vegetated than non-vegetated soils, but total N increased on average in effluent of both vegetated and non-vegetated soils relative to stormwater input. Effluent concentrations varied 2-4-fold among species for TSS, total N and P, total dissolved N (TDN), organic nitrogen and Cu, to more than 20-fold for NOx, NH4+, Mn, Pb and Fe. Species also varied markedly in pollutant removal per root mass (a means of standardising for plant size), with 18-50-fold variation among species in effluent concentrations of total P and N, TDN and organic N, to >150-fold variation in NOx and NH4+. Hence, choice of plant species may have marked effects on biofilter effectiveness.     

Reuse potential of municipal wastewater treatment facility effluents for sustainable water resource management in Ulsan,Korea

Effluent qualities of five municipal wastewater treatment facilities (MWWTFs) in Ulsan were evaluated to examine their reuse potential. Effluent from Yongyeon (Y) MWWTF, Onsan (O) MWWTF and Bangeojin (B) MWWTFs can be used as cooling water without further treatment. As evident from Langelier saturation index and Ryzner index values, reuse of treated effluent from OMWWTF and BMWWTFs is recommended by controlling the pH to reduce the scale-forming potential of effluent. However, effluents from these MWWTFs need additional treatment to remove residual dissolved constituents before reuse as boiler water. Besides, effluent from Hoiya (H) MWWTF and Unyang (U) MWWTFs can be reused for agricultural irrigation without any additional treatment. Based on the scientific results obtained from this investigation, proper application of technology and promotion of public awareness to change the traditional mindset for treated effluent reuse could immensely contribute towards conserving local water resources and addressing global environmental problems on a regional basis.     

Liquid Effluents: New Solutions to Old Problems

Effluent discharges from industrial processes will come under increasingly close scrutiny in the future, as legislation reduces the limits for discharges. Existing processes will, in many cases, be unable to meet the more stringent controls. Therefore a new generation of processes, capable of removing chemical pollutants from waste streams to nanogram levels, needs to be developed. Already the nuclear industry has extensive experience of applying some of these emerging technologies to control radioactive discharges, and is developing these processes further through the collaborative forum of AEA Technology's Effluent Processing Club so that they may be economically applied in the non-nuclear process and manufacturing industries.     

Effectiveness of an anaerobic granular activated carbon fluidized-bed bioreactor to treat soil wash fluids: a proposed strategy for remediating PCP/PAH contaminated soils

An integrated system has been developed to remediate soils contaminated with pentachlorophenol (PCP) and polycyclic aromatic hydrocarbons (PAHs). This system involves the coupling of two treatment technologies, soil-solvent washing and anaerobic biotreatment of the extract. Specifically, this study evaluated the effectiveness of a granular activated carbon (GAC) fluidized-bed reactor to treat a synthetic-waste stream of PCP and four PAHs (naphthalene, acenaphthene, pyrene, and benzo(b)fluoranthene) under anaerobic conditions. This waste stream was intended to simulate the wash fluids from a soil washing process treating soils from a wood-preserving site. The reactor achieved a removal efficiency of greater than 99.8% for PCP with conversion to its dechlorination intermediates averaging 46.5%. Effluent, carbon extraction, and isotherm data also indicate that naphthalene and acenaphthene were removed from the liquid phase with efficiencies of 86 and 93%, respectively. Effluent levels of pyrene and benzo(b)fluoranthene were extremely low due to the high-adsorptive capacity of GAC for these compounds. Experimental evidence does not suggest that the latter two compounds were biochemically transformed within the reactor.     

Reverse osmosis concentrate treatment via a PAC-MF accumulative countercurrent adsorption process

Organic pollutants in reverse osmosis (RO) concentrates from wastewater reclamation are mainly comprised of low molecular weight biorefractory compounds. Generally, advanced oxidation methods for oxidizing these organics require a relatively high level of energy consumption. In addition, conventional adsorption removal methods require a large dose of activated carbon. However, the dose can be reduced if its full adsorption capacity can be used. Therefore, the combined technology of powdered activated carbon (PAC) adsorption and microfiltration (MF) membrane filtration was studied to develop a countercurrent two-stage adsorption process. A PAC accumulative adsorption prediction method was proposed based on the verification of a PAC multi-stage adsorption capacity equation. Moreover, the prediction method was amended for a more accurate prediction of the effluent quality because adsorption isotherm constants were affected by the initial adsorbate concentration. The required PAC dose for the accumulative countercurrent two-stage adsorption system was 0.6 g/L, whereas that of the conventional adsorption process was 1.05 g/L when the dilution factor(F) was 0.1 and the COD and DOC removal rates were set to 70% and 68.1%, respectively. Organic pollutants were satisfactorily removed with less consumption of PAC. Effluent from this combined technology can be further reclaimed by an RO process to improve the overall recovery rate to between 91.0% and 93.8% with both economic and environmental benefits.     

The use of modelling to predict levels of estrogens in a river catchment: How does modelled data compare with chemical analysis and in vitro yeast assay results?

Effluent discharges at Rodbourne sewage treatment works (STWs) were assessed using chemical and in vitro biological analysis as well as modelling predictions. Results showed that Rodbourne STW discharged less estrone (E1) than expected, but similar 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) to those predicted by a widely cited effluent prediction model. The Exposure Analysis Modelling System (EXAMS) model was set up using measured effluent concentrations as its starting point to predict estrogen concentrations along a 10 km length of the receiving water of the River Ray. The model adequately simulated estrogen concentrations along the river when compared to July 2007 measured data. The model predicted combined estrogen equivalents in reasonable agreement with estrogenicity as measured by passive sampler (POCIS) extracts using the yeast estrogen screen. Using gauged mean flow values for 2007 the model indicated that the most important determinand for estrogen exposure in the Ray was not season, but proximity to the Rodbourne effluent. Thus, fish in the first 3 km downstream of Rodbourne were typically exposed to two or even three times more estrogens than those living 7-10 km further downstream. The modelling indicated that, assuming the effluent estrogen concentrations measured in February 2008 were typical, throughout the year the whole length of the Ray downstream of Rodbourne would be estrogenic, i.e. exceeding the 1 ng/L E2 equivalent threshold for endocrine disruption.     

Meeting the phosphorus consent with biological nutrient removal under UK winter conditions

It is estimated that up to 342 wastewater treatment plants (Wwtps) in England and Wales will require a phosphorus (P) consent by 2010. Although biological P removal is considered to be the most sustainable option for P removal, it has always been problematic for plants that remove both nitrogen and P due to the inadequate concentration of organic material during wet periods. Two biological nutrient removal (BNR) configurations, the Johannesburg (JHB) process and a combined JHB and five-stage Bardenpho process, were evaluated over a period of 2 years to assess the impact of sewage strength on bio-P removal. The JHB achieved an average effluent total phosphorus (TP) of 2.4 mg/L and the combined JHB and five-stage process averaged 1.4 mg/L effluent TP. The major problems affecting the performance of both configurations were: dissolved oxygen (DO) in the recycled mixed liquor, nitrate in the return activated sludge (RAS) and low influent biological oxygen demand (BOD) concentrations. Acetate dosing proved successful as a source of volatile fatty acids (VFAs) in the anaerobic zone during periods of low-strength sewage. An acetate dosing strategy based on the influent flow rate to the plant was found to be a simple and effective technique that ensured that a consent of <1 mg TP/L could be met.     

Phosphorus retention and mass balance in an integrated constructed wetland treating domestic wastewater

This study quantified the contributions of different P removal pathways in an integrated constructed wetland (ICW) treating domestic wastewater. Findings over the study period (February 2008 to March 2012) showed average P retention rates of 31 ± 2 mg/m²/day for molybdate reactive phosphate (MRP) and 40 ± 3 mg/m²/day for total P. Near complete P removal was achieved during the first 2 years of operation. Thereafter, effluent concentrations increased slightly. According to the mass balance estimation, assimilation by plants accounted for approximately 16% of the total P retained, while sediment storage contributed nearly 60%. Sediment storage was the major P removal pathway in the ICW. Thus, high effluent concentrations recorded during high effluent flow volumes was due to remobilisation of P from the sediment. Management of ICW systems may therefore require implementing sediment removal schemes. The combination of plants with high biomass production can be beneficial for improving ICW performance.     

两相厌氧工艺处理高盐纤维素醚废水的研究

采用接种特定污泥的两相厌氧反应器处理高盐纤维素醚废水,重点考察了启动过程及其处理效果。试验结果表明,当产酸相的HRT为18 h时,其所能承受的最大容积负荷为8.18kg/(m3.d),此时其对COD的去除率为20%左右;当产甲烷相的HRT为24 h时,其所能承受的最大容积负荷为5.5 kg/(m3.d),此时其对COD的去除率为35%左右;产甲烷相对COD的去除率与产酸相出水的酸化度呈显著正相关。在产酸相进水COD为6 000 mg/L、产甲烷相进水pH值为7的条件下,当产酸相进水pH值为6、HRT为18 h及产甲烷相的HRT为48 h时,系统的处理效果较佳,出水COD为1 800 mg/L,对COD的总去除率可达70%左右。     

Activated sludge treatment of abattoir wastewater—II : Influence of dissolved oxygen concentration

Performance of laboratory scale completely mixed activated sludge reactors fed with abattoir wastewater was measured at different dissolved oxygen (DO) concentrations. Degradation of fat present in the influent was inhibited at DO concentrations below about 0.5 mg l⁻¹, leading to sludges with high fat content which settled poorly due to excessive numbers of filamentous microorganisms. Fat was degraded rapidly at higher DO concentrations (up to 4.0 mg l⁻¹) and the sludge contained few filamentous microorganisms, a low fat content and settled readily. However, effluent quality was highest at low DO concentrations due to lower levels of soluble breakdown products from the fat.When wastewater was fed intermittently at constant aeration rate, sludge with a low fat content and good settleability resulted, even though the DO concentration was about 0.2 mg l⁻¹ for more than 30% of the time. Effluent quality was also high. Thus it is concluded that for full-scale abattoir treatment plants where wastewater flow is intermittent, DO concentration may be low during periods of high loading without adversely affecting effluent quality or sludge settleability.     

State detection and control of overloads in the anaerobic wastewater treatment using fuzzy logic.

The two-stage anaerobic wastewater pre-treatment was modelled and controlled. The biological state of the reactors could be predicted using a fuzzy logic system and based upon this, proper control actions were taken automatically in order to avoid an overload. The system was designed to handle very strong fluctuations in the concentration of the substrate and the volumetric loading rate. Hydrogen concentration together with methane concentration, gas production rate. pH and the filling level of the acidification buffer tank were used as input variables for the fuzzy logic system. The manipulated variables were the flow rate from the acidification buffer tank into the methane reactor, the temperature and pH of both reactors, the circulation rate of the fixed bed reactor, back flow from the methane reactor into the acidification, and the control of the feed into the acidification buffer tank. The developed control system was successfully tested on a fully automated lab scale two-stage anaerobic digester. Different types of wastewater from food processing industries were successfully applied. Even a restart of feeding with very high COD concentrations (100 gl(-1) after several days of stand by was handled successfully. Effluent concentrations could be kept low without using TOC, COD or equivalent measurements.     

Occurrence of selected surfactants in untreated and treated sewage

Several surfactants were monitored in treated and untreated sewage in nine municipal wastewater treatment plants (WWTPs) in western Austria. The nine sampled WWTPs cover a wide variety referring to size and applied treatment technology. The investigation focused on linear alkylbenzene sulphonate (LAS), quaternary ammonia compounds (QAC), nonylphenol (NP), octylphenol (OP), nonylphenolmono- (NP(1)EO) and -diethoxylates (NP(2)EO). Whereas LAS, NP, OP and NP(1,2)EO were analysed separately in the liquid phase and in the solid phase, the QACs were measured in the total sample. Total influent concentrations of LAS varied between 2.4 mg l(-1) up to 6.7 mg l(-1) whereas total effluent concentrations were in the lower microg l(-1) range (11-50 microg l(-1)). Whichever the type of treatment, a clear removal during treatment was observed. Solid liquid distribution coefficients K(d) were calculated for untreated sewage. The calculated K(d) values varied between 1300 and 3900 l kg(-1). OP was of minor importance with total influent concentrations below 1microg l(-1). NP and NP(1,2)EO were present in all analysed influents in concentrations between 1 and 35microg l(-1). Effluent concentrations were notably lower than the measured influent concentrations. K(d) values for NP varied between 500 and 6600 l kg(-1), for NP(1)EO between 800 and 2700 l kg(-1) and for NP(2)EO between 100 and 1800 l kg(-1). From the QACs several alkyl benzyl (BAC), dialkyl (DDAC) and trialkyl (ATAC) ammonium chlorides with varying alkyl chain lengths were analysed. Highest total concentrations in the influents to the WWTPs were observed for the BAC-C12 and the ATAC-C16 homologues. Effluent concentrations were notably lower compared to influent concentrations, indicating removal by adsorption and/or biodegradation. The influence of the removal by adsorption increased with increasing alkyl chain length.     

EGSB/生物接触氧化/BAF工艺处理葡萄糖生产废水

采用“EGSB-生物接触氧化-BAF”联合工艺处理葡萄糖生产废水，着重研究了pH值和容积负荷对EGSB反应器去除效果的影响。结果表明，以厌氧颗粒污泥作为EGSB的接种污泥，30d左右便可完成启动，且能形成灰黑色和黑色颗粒污泥；采用出水回流和人为投加碱性物质可以增强系统的缓冲能力，有效缓解系统酸碱平衡失调。当进水COD为3000～4000mg／L、SS为800～1000mg,／L、NH3-N为15～20mg／L时，采用该联合工艺处理后，对COD、SS和NH3-N的平均去除率分别达98％、92％和78％，处理效果好而且稳定。     

粉煤灰深度处理二级出水中磷的实验研究

为了探索除磷的优良吸附材料和新方法,本实验对粉煤灰与PFS联用、碱改性粉煤灰处理二级出水中的磷进行了实验研究,结果表明：粉煤灰与PFS联用处理3 mg/L的含磷模拟废水去除率可达72%,两者联用可使吸附与混凝发挥协同作用,强化处理效果;而用2 mol/L的氢氧化钠碱改性粉煤灰后,当投加改性粉煤灰8 g,以30 r/min的转速搅拌5 min时,对含磷模拟废水的去除率可达90%,碱改性后,粉煤灰在发挥其吸附作用的同时,与磷酸根离子产生羟磷灰石化学沉淀,强化了除磷效果,且可实现泥水分离。比较分析上述2种方法,碱改性粉煤灰既能有效除磷又能实现泥水分离,且药剂成本较低,工艺简单,值得推广应用。     

Fate of linear alkylbenzene sulfonate (LAS) in activated sludge plants

Monitoring data were collected in a pilot-scale municipal activated sludge plant to assess the fate of the C12-homologue of linear alkyl benzene sulfonate (LAS-C12). The pilot-plant was operated at influent LAS-C12 concentrations between 2 and 12 mg l(-1) and at sludge retention times of 10 and 27 days. Effluent and waste sludge concentrations varied between 5 and 10 microg l(-1) and between 37 and 69 microg g(-1) VSS, respectively. In the sludge samples only 2-8% was present as dissolved LAS-C12, whereas the remaining 92-98% was found to be adsorbed to the sludge. In spite of this high degree of sorption, more than 99% of the LAS-C12 load was removed by biodegradation, showing that not only the soluble fraction but also the adsorbed fraction of LAS-C12 is readily available for biodegradation. Sorption and biodegradation of LAS-C12 were also investigated separately. Sorption was an extremely fast and reversible process and could be described by a linear isotherm with a partition coefficient of 3.2 l g(-1) volatile suspended solids. From the results of biodegradation kinetic tests it was concluded that primary biodegradation of LAS-C12 cannot be described by a (growth) Monod model, but a secondary utilisation model should be used instead. The apparent affinity of the sludge to biodegrade LAS-C12 increased when the sludge was loaded with higher influent concentrations of LAS-C12.     

粉煤灰加速启动异波折流板厌氧反应器的研究

采用异波折流板厌氧反应器处理污水处理厂初沉池出水,以加入粉煤灰的厌氧污泥为接种污泥,考察了粉煤灰对该厌氧反应装置的加速启动效果.结果表明在接种污泥中加入粉煤灰可大大缩短启动时间,反应器连续运行55 d即可启动成功.此时系统对COD的平均去除率为72.9%,厌氧污泥的性状较刚接种时发生了较大的变化,最大比甲烷产生量从0.34 mL/(gVSS·h)提高到2.13 mL/(gVSS·h).     

Advanced phosphorus removal from membrane filtrates by adsorption on activated aluminium oxide and granulated ferric hydroxide

The advanced phosphorus (P) removal by adsorption was studied for its suitability as a post-treatment step for membrane bioreactor (MBR) effluents low in P concentration and particle content. Two commercial adsorbents, granulated ferric hydroxide (GFH) and activated aluminium oxide (AA), were studied in batch tests and lab-scale filter tests for P adsorption in MBR filtrates. GFH showed a higher maximum capacity for phosphate and a higher affinity at low P concentrations compared to AA. Competition by inorganic ions was negligible for both adsorbents at the original pH (8.2). When equilibrium P concentrations exceeded 2 mg L(-1) in the spiked MBR filtrates, a precipitation of calcium phosphates occurred additionally to adsorption. During column studies the effluent criteria of 50 microgL(-1) P was reached after a throughput of 8000 bed volumes for GFH and 4000 for AA. Dissolved organic carbon appears to be the strongest competitor for adsorption sites. A partial regeneration and reloading of both adsorbents could be achieved by the use of sodium hydroxide.     

Book Reviews

Cutting Water and Effluent Costs (Second Edition), by J. H. Hills.
Household Waste Recycling, by R. Waite.     

Chemical coagulation of combined sewer overflow: heavy metal removal and treatment optimization

The coagulation of combined sewer overflow (CSO) was investigated by jar-testing with two commercial coagulants, a ferric chloride solution (CLARFER) and a polyaluminium chloride (WAC HB). CSO samples were collected as a function of time during various wet-weather events from the inlet of Boudonville retention basin, Nancy, France. Jar-tests showed that an efficient turbidity removal can be achieved with both coagulants, though lower optimum dosages and higher re-stabilization concentrations were obtained with the aluminum-based coagulant. Optimum turbidity removal also yielded effective heavy metal elimination. However, the evolution with coagulant dosage of Cu, Zn, Pb, Cr, soluble and suspended solids contents followed various patterns. The removal behaviors can be explained by a selective aggregation of heavy metal carriers present in CSO and a specific interaction between hydrolyzed coagulant species and soluble metals. Stoichiometric relationships were established between optimal coagulant concentration, range of optimal dosing, and CSO conductivity, thus providing useful guidelines to adjust the coagulant demand during the course of CSO events.     

The behaviour of nitrilotriacetic acid during the anaerobic digestion of sewage sludge

In laboratory simulations of the anaerobic sludge digestion process, the impact of the detergent builder nitrilotriacetic acid (NTA) on digester efficiency has been studied. It was concluded that NTA at concentrations up to 30 mg l⁻¹ had no adverse effect on anaerobic digestion. However, analysis of the digested sludge indicated that only 29–45% of the influent NTA was removed during treatment. To differentiate between biological and physical processes of removal, biological activity in the digesters was arrested by the addition of sodium azide. Effluent NTA concentration did not increase indicating that biological activity was not responsible for the removal observed.Batch experiments undertaken to evaluate NTA solubility in digested sludge (containing azide) at two solids concentrations indicated a decrease in soluble NTA with increasing solids concentration.It is concluded that the removal of NTA observed during anaerobic digestion was not biological and in part was the result of adsorption onto the solid phase.