plc 外文翻译

Comparative analysis of ef?uent water quality from a municipal

treatment plant and two on-site wastewater treatment systems

Santos N.Garcia a ,b ,Rebekah L.Clubbs a ,c ,Jacob K.Stanley a ,b ,c ,Brian Scheffe a ,c ,d ,Joe C.Yelderman Jr.c ,d ,e ,Bryan W.Brooks a ,c ,d ,?

a

Department of Environmental Science,Baylor University,One Bear Place #97266,Waco,TX 76798,USA b

Department of Biology,Baylor University,One Bear Place #97266,Waco,TX 76798,USA c

Center for Reservoir and Aquatic Systems Research,Baylor University,One Bear Place #97266,Waco,TX 76798,USA d

Baylor Wastewater Research Program,Baylor University,One Bear Place #97266,Waco,TX 76798,USA e

Department of Geology,Baylor University,One Bear Place #97266,Waco,TX 76798,USA

h i g h l i g h t s

A novel facility was used for comparison of onsite and centralized ef?uent quality. Water quality was assessed by traditional measures,toxicity and steroid levels. Ef?uent quality from an aerobic onsite system was similar to a centralized system. Performance-based measures appear useful for evaluations of onsite ef?uent quality .

a r t i c l e i n f o Article history:

Received 1August 2012

Received in revised form 25February 2013 Accepted 6March 2013

Available online 1April 2013 Keywords:On-site

Endocrine disrupting compounds Whole ef?uent toxicity Water quality Septic

Wastewater treatment

a b s t r a c t

Though decentrali z ed on-site technologies are extensively employed for wastewater treatment around

the globe,an understanding of ef?uent water quality impairments associated with these systems remain less understood than ef?uent discharges from centralized municipal wastewater treatment https://www.sodocs.net/doc/fc6331299.html,ing a unique experimen t al facility,a novel comparative analysis of ef?uent water quality was per- formed from model decentralized aerobic (ATS)and septic (STS)on-site wastewater treatment systems and a centralized municipal wastewater treatment plant (MTP).The ATS and STS units did not bene?t from further soil treatment.Each system received common in?uent wastewater from the Waco,Texas,USA Metropolitan Area Regional Sewerage System.We tested the hypothesis that MTP ef?uent would exhib i t higher water quality than on-site ef?uents,based on parameters selected for study.A tiered test- ing approach was employed to assess the three ef?uent discharges:select routine water quality param- eters (Tier I),whole ef?uent toxicity (Tier II),and select endocrine -active compounds (Tier III).Contrary to our hypothesis,ATS ef?uent was not statistically different from MTP ef?uents,based on Tier I and III parameters ,but reproductive responses of Daphn i a magna were slightly more sensitive to ATS than MTP ef?uents.STS ef?uent water quality was identi?ed as most degraded of the three wastewater treat- ment systems.Parameters used to assess centralized wastewater treatment plant ef?uent water quality such as whole ef?uent toxicity and endocrine active substances appear useful for water quality assess- ments of decentrali z ed discharges.Aerobic on-site wastewater treatment systems may represent more robust options than traditional septic systems for on-site wastewater treatment in watersheds with appreci a ble groundwater –surface water exchange.

ó2013 Elsevier Ltd.All rights reserved.

1.Introduction

Quanti?cation of water quality impairment presents challenges to water resource managers because water quality is a term that is often poorly de?ned among aquatic scientists ,engineers,manag- ers,and policy makers (Parparov et al.,2006 ).In the United States,water quality of ef?uents released from centralized municipal and industria l wastewater treatment plants is regulated by the US Environm e ntal Protection Agency’s (US EPA)National Pollutant Discharge Elimination System program (Grothe et al.,1996 ).Under this program,water quality is evaluated by screening speci?c water quality parameters (e.g.,metals,nutrients,pathogens,pesti- cides)against established criteria,and by whole ef?uent toxicity,

0045-6535/$-see front matter ó2013 Elsevier Ltd.All rights reserved.https://www.sodocs.net/doc/fc6331299.html,/10.1016/j.chemosphere.2013.03.007

?Corresponding author at:D epartment of Environmental Science,Baylor Uni- versity,One Bear Place #97266,Waco,TX 76798,USA.Tel.:+1254 710 6553;fax:+1254 710 3409.

E-mail address:Bryan_Brooks@https://www.sodocs.net/doc/fc6331299.html, (B.W.Brooks).

which employ model organisms such as the cladoceran Daphnia magna to integrate chemical ,physical,and biological conditions of an ef?uent through quanti?able biological responses (US EPA, 2002a).

US EPA reports that approximately 1in4American households (an estimated 60million people),up to a third of new homes,and over half of the mobile homes in the United States rely on on-site treatment systems to treat wastewater (US EPA,2002b,2005 ).His- torically,septic treatment systems (STSs)have been most com- monly used for decentralized on-site treatment of wastewater. Over half of these septic systems are more than 30years old and at least 10%are estimated to be malfunctioning (US EPA,2002b, 2005).Failure rates for on-site systems have been reported to be up to70%in select areas (US EPA,2002b ).These failures can degrade water quality in watersheds,potentially impacting ecosystem or human health (US EPA,2002b ).An alternative to STS are aerobic treatment systems (ATSs),which represent a newer generation of on-site technolo g ies with generally improved treatment capabili- ties (Jantrania and Gross,2006 ).In fact,ATS are required by regula- tory agencies in select regions experiencing high groundwater exchange with surface water bodies (Jantrania and Gross,2006 ).

Potential ecological impacts of failing or poorly installed on-site wastewater treatment systems are varied,but often include nutri- ent-enhanced productivity and bacterial contaminat i on of aquatic systems (US EPA,2002b ).More recently,several studies have iden- ti?ed endogen o us and exogenou s compound s with endocrin e activity in on-site wastewater or groundwater in?uenced by on- site systems (Rudel et al.,1998;D eJong et al.,2004;Conn et al., 2006;Swartz et al.,2006;Stanford et al.,2010 ).Endocrine active substances and other contaminan t s of emerging concern present challenges for such historical approach e s to assess wastewater quality (Brooks et al.,2009 ),particularly in regions in?uenced by municipal wastewater discharges (Brooks et al.,2006 ).Such intro- ductions of these contaminan t s of emerging concern from diffuse decentralize d ef?uents may be particularly relevant to aquatic sys- tems located adjacent to areas with dense concentr a tions of on-site systems because endocrine active compounds such as endogenous steroids may impact the reproduction of aquatic vertebrates (Pur-dom et al.,1994;Huggett et al.,2003;Jobling et al.,2006;Dobbins et al.,2008 ).

Whole ef?uent toxicity methodol o gies or other biological re- sponses are often incorporate d in evaluations of water quality from centralized ef?uent discharges (Grothe et al.,1996 ),but these ap- proaches have not been employed to assess on-site ef?uent water quality.Unfortunately,the quality of on-site ef?uent discharges is often only quanti?ed with basic measures of water quality such as Total Suspende d Solids (TSSs)or Carbonaceous Biochemical Oxy- gen D emand (CBOD;TNRCC,2002 ),which provide limited infor- mation on potential impacts of ef?uents to aquatic life.Further, even less is known about the magnitude,duration or frequency of exposure to endocrine active contaminan t s or whole ef?uent toxicity from various on-site system technologies.

Here we tested the hypothes i s that a centralized MTP ef?uent discharge would exhibit higher water quality,based on selected parameters,than model on-site STS and ATS ef?uents.A critical component of our study was use of a unique experimental facility, which provided a globally unique setting to conduct such a study because common in?uent wastewater is diverted from a central- ized wastewa t er treatment plant to model STS and ATS.We devel- oped a tiered testing approach to assess the three ef?uent types, including select water quality parameters (Tier I),whole ef?uent toxicity (Tier II),and select endocrin e-active compound s(Tier III). To our knowled g e,this experime n tal facility provided for a novel assessment of ef?uent water quality from a centraliz e d and two common decentralized treatment systems receiving a common wastewater in?uent.2.Materials and methods

2.1.Study site description and experimen t al design

This study was performed at the Baylor Wastewater Research Program site (Fig.1),located at the Waco Metropolitan Area Regio- nal Sewerage System in Waco,Texas,USA,adjacent to the National Sanitation Foundation Internationa l’s wastewater test facility for on-site systems.The Waco Metropolitan Area Regional Sewerage System is an activated sludge treatment plant (MTP)with a design capacity of approximat e ly 151 ML per day and a mean daily load of about 95ML per day.In?uent from this facility is continuously di- verted to the Baylor Wastewa t er Research Program and National Sanitation Foundation facilities,in which it is further partitioned to various on-site wastewater treatment technologie s for study (Fig.1).We selected an advanced aerobic treatment plant (ATS) and a typical STS as model systems for a comparative ef?uent water quality evaluation to the MTP.The ATS included a5678 L multi-chamber e d system that was conceptu a lly similar to the MTP because it contained an activated sludge process.The ATS used in this study also included a pretreatmen t tank,an aeration chamber and a?nal clari?er(HOOT Systems,Lake Charles,Louisi- ana,USA),but did not receive bene?t from additional soil treat- ment.The STS was a basic,two-chamb e red 2800-l tank with no ?lter on the ef?uent discharge and also without bene?t of a soil treatment unit,which may simulate a malfunctioni n g septic sys- tem scenario.

Hydrologi c retention times of the MTP,ATS,and STS were con- sidered in order to effectively compare ef?uent treated by the MTP to ef?uents treated by the ATS and STS.The MTP had a theoretical hydrologi c retention time of approximat e ly 8h(Mike Jupe,City of Waco,https://www.sodocs.net/doc/fc6331299.html,m.),whereas the ATS and STS both had retention times of$2.3 d based on dye tracer studies.Subsequentl y,5L of ef?uent from each treatment plant was collected on its corre- sponding sample day on six sampling dates over a three week per- iod during summer conditions.Ef?uents were collected from the on-site systems prior to soil in?ltration,which was intended to model worst case loadings to the environment with limited to no soil treatment.Because population demograph i cs may in?uence

S.N.Garcia et al./Chemosphere 92(2013)38–4439

estrogenicit y of wastewater ef?uent(Brooks et al.,2003;Hemmin g et al.,2004;Martinovi c et al.,2008 ),a sampling design included three samples to evaluate weekend in?uent wastewater and three samples were selected to represent in?uent on weekday s.

To assess ef?uent water quality among the three wastewater treatment systems,a tiered testing approach was employed ,which assessed routine water quality variables (Tier I paramete r s),whole ef?uent toxicity using a21d D.magna bioassay (Tier II parame- ters),and levels of select endocrine-acti v e steroids in wastewater ef?uents(Tier III paramete r s).Each level of the tiered testing re- gime included parameters that provided increasingly detailed information on ef?uent constituents and their potential impacts to aquatic life.

2.2.Water quality parameters

CBOD and TSS were quanti?ed from each system following standard procedures (APHA et al.,1995 ).TSS and CBOD represent the only two measurements required by the Texas Commission on Environmental Quality to assess ef?uent quality from on-site treatment systems.Conductivi t y was measure d using a Hydrolab Quanta (Loveland,Colorado,USA);alkalinity and pH were quanti- ?ed using a model 720A Orion bench top pH meter (Beverly,Mas- sachusetts,US)according to standard methods (APHA et al.,1995 ).

Ammonia (NH3),nitrite (NO2),and nitrate (NO3)levels were as- sessed because they were previously identi?ed in on-site wastewa- ter ef?uents to cause ecosystem impacts (Jones et al.,2004 ).A HachòsensION (Loveland,Colorado,USA)ion selective electrode was used to quantify NH3levels.A Hach òspectrophot o meter (Loveland,Colorado,US)was employed to determine NO3and NO2levels.D etection limits for NO3and NO2were 0.3 mg Là1 and 0.002 mg Là1,respectively,while the detection range for the ammonia ISE was 0.05–17000mg Là1NH3.

2.3.Whole ef?uent toxicity

Standard US EPA bioassay methods for D.magna were used to assess toxicity in each ef?uent(US EPA,1996,2002a ).A prelimin- ary 96h.acute toxicity test (Test Method 2021.0)was performed prior to initiating a longer term study to identify potential acute toxicity of the MTP,ATS and STS ef?uents and to establish ef?uent treatment levels for whole ef?uent toxicity experime n ts (US EPA, 2002a).Subseque n tly,ef?uent toxicity to D.magna mortality, growth,and reproduction was assessed over a21-d exposure per- iod following standardized methods (US EPA,1996 )with minor modi?cations previously reported by our group (Clubbs and Brooks,2007 ).Following sample collection,ef?uents were stored at4°C for less than 96h prior to study initiation or test solution renewals (US EPA,2002a ).Each ef?uent was diluted with reconsti- tuted hard water to?ve concentr a tions following a0.5 dilution fac- tor.Reconstituted hard water served as a control,and was prepared according to standard methods (APHA et al.,1995 ).So- matic growth of each surviving female was determined as dry weight with a Mettler Toledo MX5 microbalance (Columbus,Ohio, USA).

2.4.Steroids

Each ef?uent sample was pre-?ltered with Millipore òglass-?-ber ?lters(Bedford,MA,US)and extracted with 3M Empore òC18 solid phase extraction disks (St.Paul,MN,USA)to pre-concen- trate samples (Li et al.,2004 ).C18 solid phase extraction disks were stored atà40°C for less than 40d until analysis.C18 solid phase extractio n disks were washed with 5mL of nanopure water and 5mL hexane,then eluted with 5mL of dichlorometha n e.Sam- ples were then taken to dryness with a Turbovap ò(Caliper Life Sciences,Hopkinton,MA,USA)under nitrogen,and reconstituted in1mL of10%MeOH.Quanti?cation of testosterone (T),estrone (E),17b-estradio l(E2)and 17a-ethinyl estradiol (EE2)were per- formed using commerciall y available enzyme-linked immunoad- sorbent assays used for environm e ntal diagnost i c applications: Cayman Chemical (Ann Arbor,MI,USA)for E2and T;R-Biopharm (South Marshall,MI,USA)for EE2;and Ecologiena (Tokyo,Japan) for E1.Extraction ef?ciencies for matrix spikes ranged from 87% to127%;target steroids were not detected in?eld blanks.

2.5.Statistica l analyses

Fisher’s Exact Test was performed to test for signi?cant differ- ences in D.magna immobilization among ef?uent sample dilutions and control responses (TOXSTAT,Cheyenne,Wyomin g,USA).ANO- VA with Dunnett’s Test,Wilcoxon’s Rank Sum Test,and Bonferron- i’s T-test were used,as appropriate ,to detect identify signi?cant differenc e s in D.magna growth and reproducti o n from controls (a=0.05).No Observed Effect Concentration (NOEC)and Lowest Observed Effect Concentr a tion (LOEC),based on dilution percent- age,were determined for each ef?uent type.One-way ANOVAs with Student–Newman–Keuls post hoc tests (a=0.05)was per- formed using SAS (Version8.2,Cary,NC,USA)to detect differenc e s between MTP,ATS,and STS nutrient and endocrin e active com- pound levels and standard water quality measures.

3.Results and discussion

The primary objective of the present study was to assess and compare the ef?cacies of a model MTP,an ATS,and a STS to treat wastewa t er because literature concerning their relative capabili- ties are lacking.Final ef?uent of MTP,ATS and STS systems were examine d prior to additional dilution or treatment (e.g.,instream dilution of MTP,soil treatment of ATS,STS)to characteri z e worse case scenarios for environmental discharges.We hypothes i zed that the MTP would be the most effective in treating wastewater and thus MTP ef?uent would have the highest ef?uent water quality as assessed by three tiers of measure s.This hypothesis was not uniformly supported.

3.1.Water quality parameters

Contrary to previous observations from other locations (Brooks et al.,2003;Hemming et al.,2004;Martinovic et al.,2008 ),no sig- ni?cant differences (p>0.05)were observed between weekday and weekend samples;thus,weekend and weekday data for water quality paramete r s and steroids were combined for statistical anal- yses.In the present study,STS ef?uent generally had the lowest water quality as assessed by Tier I paramete r s.STS ef?uent exhib- ited signi?cantly higher alkalinity,conductivity,TSS,and CBOD (Table 1)than MTP and ATS ef?uent samples (p<0.05).In the State of Texas,USA,for example,CBOD and TSS criteria were established by the Texas Commission on Environmental Quality at60mg Là1 and 65mg Là1,respectively (TNRCC,2002 ).In fact,CBOD and TSS represent the only water quality parameters historically assessed to assess ef?uent water quality from decentralized systems (Jantrania and Gross,2006 ).Although STS failed to meet both of these TSS and CBOD single grab criteria,the ATS and MTP ef?uents did not exceed CBOD and TSS criteria for on-site systems during the present study (Fig.2).

Nutrient discharges from onsite systems are receiving increased attention from environmental managers and regulators,particu- larly for groundwate r resources,coastal regions or inland water bodies experiencing exceedance s of bacteria water quality stan- dards,eutrophicati o n and harmful algae blooms (Humphre y et al.,2010,2011;Withers et al.,2011;Brooks et al.,2011;Pujari

40S.N.Garcia et al./Chemosphere 92(2013)38–44

et al.,2012 ).Similar to observations for TSS and CBOD,NH3levels in the present study were signi?cantly higher in STS ef?uent;how- ever,NO2levels were not signi?cantly different among MTP,ATS, and STS ef?uents(p<0.05)(Table 2).Though NO3levels in MTP and STS were not signi?cantly different (p<0.05),ATS ef?uent contained signi?cantly higher NO3levels (p>0.05;Table 2).Thus, with the exception of these NO3observations ,ef?uent water quality from ATS and MTP systems were generally compara b le, based on Tier I paramete r s evaluated in the present study.It is important to note,however ,that nutrient loadings from point and non-poin t source ef?uent are often accompanied by other con- taminants ,which may present risks to aquatic life uses (Brooks et al.,2008;Fulton et al.,2009,2010;Bian et al.,2013 ).

3.2.Whole ef?uent toxicity

Toxicity studies with aquatic organisms such as D.magna are routinely employed to monitor the quality of surface waters and ef?uent discharges from centralized wastewa t er treatment plants (US EPA,2002a ),and to assess the environmental safety of indus- trial chemicals (US EPA,1996 ). D.magna survival,growth and reproduction were selected as Tier II indicators of ef?uent water quality in the present study because ef?uents not possessing chronical l y toxic conditions to cladocerans are considered to be protectiv e of aquatic life uses (US EPA,2002c ).In the case of decen- tralized ef?uent discharges,little to no data for aquatic toxicity ex- ists from on-site systems (Berto et al.,2009 ).Thus,to our knowled g e the present study provides the ?rst assessment of aquatic toxicity of two different onsite technologie s and a central- ized ef?uent receiving a common in?uent wastewater source.

Table 1

Mean water quality measurements (±SD)for the ef?uents of a municipal wastewater treatmen t plant and two on-site wastewater treatmen t systems in the Waco Metropolitan Area Regional Sewerage System over a21d period.One-way ANOVA with Studen t–Newman–Keuls post hoc test (a=0.05).Mean values with the same letter are not signi?cantly different (p<0.05).

Ef?uent Alkalinity (mg Là1as CaCO 3)Hardness (mg Là1as CaCO 3)pH Conductivity (mS cmà1)

MTP a(n=7)211 (±25.4)A198 (±32.3)A7.527 (±0.088)A0.959 (±0.0304)A Weekdays (n=4)205 (±27.6)201 (±31.0)7.496 (±0.079)0.956 ±(0.0400) Weekends (n=3)220 (±15.0)193 (±34.0)7.568 ±(0.079)0.964 (±0.0182) ATS b(n=7)162(±14.4)e B204(±21.5)d A7.764 (±0.075)d A0.990 (±0.0343)A Weekdays (n=4)163 (±20.8)e199 (±16.1)e7.796 (±0.064)e0.986 (±0.0388) Weekends (n=3)160 (±8.66)209 (±28.4)7.731 (±0.083)0.994 (±0.0349) STS c(n=7)380 (±6.32)d C207 (±30.8)d A7.405 (±0.289)d A 1.149 (±0.0667)B Weekdays (n=4)383 (±5.77)e195(±18.5)e7.398 (±0.193)e 1.150 (±0.0894) Weekends (n=3)377 (±5.77)219 (±40.1)7.411 (±0.414) 1.148 (±0.0370)

a MTP =Municipal treatment plant.

b ATS =Aerobi

c treatment system.

c STS =Septic treatment system.

d n=6.

e n=3.

Table 2

Mean nitrog e n species measurements (±SD)of the ef?uents of a municipal waste-

water treatment plant and two on-site wastewater treatment systems in the Waco

Metropolitan Area Regional Sewerage System over a21d period.One-way ANOVA

with Student–Newman–Keuls post hoc test (a=0.05).Mean values with the same

letter are not signi?cantly different (p<0.05).

Ef?uent NH3(mg Là1)NO2(mg Là1)NO3(mg Là1)

MTP a(n=7)0.270 (±0.225)A0.06 (±0.1)d A6(±4)A

Weekdays (n=4)0.150 (±0.220)0.08 (±0.1)e7.9 (±4.4)

Weekends (n=3)0.430 (±0.112)0.01 f4(±4)

ATS b(n=7)0.0911 (±0.0449)A0.083 (±0.021)g A20(±7.2)B

Weekdays (n=4)0.0686 (±0.0180)0.087 (±0.028)e24(±1.8)

Weekends (n=3)0.121 (±0.0565)0.076 f14(±8.3)

STS c(n=7)25.1 (±6.52)B0.012 (±0.008)e A2(±2)h A

Weekdays (n=4)25.1 (±7.51)0.021 f2(±2)e

Weekends (n=3)25.0 (±6.56)0.008 i2(±3)

a MTP =Municipal treatment plant.

b ATS =Aerobi

c treatment system.

c STS =Septic treatment system.

d n=4.

e n=3.

f n=1.

g n=5.

h n=6.

i n=2.

S.N.Garcia et al./Chemosphere 92(2013)38–4441

All study systems caused signi?cant D.magna mortality in undi- luted whole ef?uent samples (100%treatment level;Fig.3). Though D.magna survival and sublethal responses (growth,repro- duction)were examined for each ef?uent discharge,the sublethal reproduction endpoint is almost always more sensitive to environ- mental contaminan t s and ef?uents than survival and somatic growth.Whereas D.magna mortality and growth endpoints exhib- ited identical NOECs (50%ef?uent)for MTP and ATS discharges, chronic toxicity was slightly greater in the ATS system:reproduc- tion NOEC values were 50%ef?uent for the MTP and 25%ef?uent for the ATS systems,respectively (Fig.3).Because the whole ef?u-ent toxicity critical dilution limit for the Waco Metropolita n Area Regional Sewerage System’s National Pollution Discharge Elimina- tion System permit is$50%,a NOEC of50%dilution level indicated that the MTP was likely operating normally during this study.STS ef?uent was most hazardous to D.magna ,as an eightfold difference in mortality and growth NOECs was observed among the STS sys- tem and MTP and ATS ef?uents(Fig.3).Based on whole ef?uent toxicity to D.magna survival,growth and reproduction,water qual- ity of ef?uent discharges were observed to be MTP P ATS >STS. 3.3.Steroids

Several endocrine active compounds were selected for a Tier III evaluation of ef?uent water quality.Similar to observations for other water quality paramete r s,no signi?cant differences (p> 0.05)were observed for steroid concentratio n s between weekday and weekend samples.Of the steroids examine d,mean E1(an E2 metaboli t e)concentratio n s were signi?cantly higher (p<0.05) than other steroids.Ef?uent levels of E1,E2,and T did not signi?-cantly differ between MTP and ATS ef?uent samples over the study period (p<0.05;Fig.4).These ef?uent concentratio n s from MTP and ATS discharges were generally consisten t with previous litera- ture for municipal ef?uents.Belfroid et al.(1999)reported E1and E2median concentr a tions of0.9 and 4.5 ng Là1,respectively,in ef?uents of?ve wastewater treatment plants in the Netherla n ds. In the same study,E2and EE2 concentratio n s for most of the ef?u-ent samples were reported to be below the limits of detection.In a study comparing the steroid estrogens from 17MTPs across Eur- ope,Johnson et al.(2005)reported that E2concentrations were usually below the detection limit,and EE2 was detected in only one of the MTPs samples at1.1 ng Là1.In the present study,con- centrations of E1,E2,EE2,and T were variable,however ,ranging from 0.97 to117 ng Là1,which likely re?ected the variable compo- sition of sewage in?uent during the study period.Nevertheles s,E1, E2,and T levels were signi?cantly higher in STS ef?uents than ATS and MTP ef?uent discharges (p<0.05;Fig.4),and observation that was generally consistent with observations for Tiers I and II water quality indicators.

42S.N.Garcia et al./Chemosphere 92(2013)38–44

Though no study has examined compara t ive water quality of onsite and centralized systems as we have done here,a few studies have examine d steroids and other contaminants of emerging con- cern in onsite systems.Standley et al.(2008)documented the pres- ences of endogenous hormones and pharmac e uticals in surface waters fed by aquifers receiving discharge from onsite septic treat- ment plants.E2and progesteron e were detected in a lower resi- dential density pond in concentratio n s of 2.2 and 0.73 ng Là1. Androstene d ione,E1,and progesterone were detected in several higher density residenti a l ponds in concentr a tions ranging from 1.4–3.3,1.2–3.0,and 0.72–6.5ng Là1;E1was detected in one of these ponds at a concentratio n of less than 2.0 ng Là1(Standley

et al.,2008 ).Swartz et al.(2006)reported the presence of steroid hormones and other endocrin e disrupting compound s in ground- water affected by a residential septic system.E1and E2concentra- tions in the contaminated ground water were found to range from 49–74ng Là1to16–19ng Là1,respectively.Several xenoestrogens such as nonylphe n olethoxylate degradation products were de- tected as well.Nonylpheno l and nonylphenol monoethox y carb- oxylate concentrations ,for example,ranged from 10–16l g Là1to 7.8–8.2l g Là1,respectively.Similarly Conn et al.(2006),examined nonylphenol e thoxylates,nonylphenolethox y carboxylates and nonlyphenol in both anaerobic and aerobic onsite systems with median values ranging from 1.0 to25l g Là1.Despite these studies,

an understa n ding of aquatic risks of contaminants of emerging concern derived from onsite systems are largely lacking.Future studies are necessary to determine if there are seasonal changes in compara t ive performance of ATS,STS,and MTP treatment and associated risks to environm e ntal quality.

4.Conclusions

Here we performed a novel comparative examination of ef?u-ent water quality from two common types of onsite wastewater treatment technologie s and a conventional municipal treatment plant receiving common in?uent wastewater .Ef?uent water qual- ity,based on conventional water quality parameters (e.g.,TSS, CBOD,nutrients;Tier I),whole ef?uent toxicity (Tier II)and steroid concentratio n s(Tier III),of an aerobic onsite system was generally comparable to a conventional municipal treatment plant.Septic ef?uent,as hypothesized,possessed the lowest water quality based on three measure m ent tiers.It is important to note that ATS and STS ef?uent typically receive additional treatment by soil following discharge to the environment.However,in areas with appreciabl e groundwate r–surface water exchange,ATS systems appear to rep- resent more robust options of onsite wastewa t er treatment.

In contrast to the water quality-based approach applied to cen- tralized wastewater treatment systems and nonpoint source con- tamination under the US Clean Water Act,as one example of an international regulation,approach e s used to evaluate decentral- ized wastewa t er systems have historical l y focused on prescripti v e codes that specify the means or methods required to achieve de- sired managemen t goals.However,because environmental condi- tions vary across the diverse global landscape,prescriptive codes have not performed equally well around the globe,particularly in those watersheds experienci n g appreciabl e groundwate r–surface water exchange .For example,there appears to be some interest in developing performance-b a sed regulations that focus on water quality-based results rather than the method of treatment (NOWRA,2006;Otis et al.,2001 ).Performance-bas e d codes would decidedly advance the science and could allow for the applicati o n

of different methods in different settings to achieve desired ef?u-ent water quality-based goals,which will support protection of public health and the environment.Whole ef?uent toxicity and measures of contaminan t s of emerging concern may contribute to this end by providing evaluation methods for on-site systems that are more focused on water quality-based treatment perfor- mance than prescriptive in nature.

Acknowled g ements

This research was supported by the Baylor Wastewater Re- search Program,the D epartment of Environmental Science and the Department of Biology Undergraduate Summer Research Pro- gram.We thank David Jumper with National Sanitation Foundation Internationa l and Ron Suchechi with Hoot Aerobic Systems for assistance with facility developmen t.Elizabeth Glidewell,Ali Al-Nahar i,Nick Harrel and Fabiola Urena-Bo e ck provided assis- tance with ?eld sampling and general laborator y assistance.Tom Conry and Mike Jupe with the City of Waco Water Utilities provided invaluable project support.

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44S.N.Garcia et al./Chemosphere 92(2013)38–44

PLC外文翻译

外文翻译 原文：The open system merit of Computer Numerical Control The open system merit is the system simple, the cost low, but the shortcoming is the precision is low. The reverse gap, the guide screw pitch error, stop inferiorly can affect the pointing accuracy by mistake. Following several kind of improvements measure may cause the pointing accuracy distinct improvement. 1. reverse gap error compensates The numerical control engine bed processing cutting tool and the work piece relative motion is depends upon the drive impetus gear,the guide screw rotation, thus the impetus work floor and so on moves the part to produce moves realizes. As traditional part gear, guide screw although the manufacture precision is very high, but always unavoidably has the gap. As a result of this kind of gap existence, when movement direction change, starts the section time to be able to cause inevitably actuates the part wasting time, appears the instruction pulse to push the motionless functional element the aspect. This has affected the engine bed processing precision, namely the instruction pulse and actual enters for the step does not tally,has the processing error therefore, the split-ring numerical control system all establishes generally has the reverse gap error compensatory function, with by makes up which wastes time the step reverse gap difference compensates is first actual reverse enters for the error, converts the pulse equivalent number it, compensates the subroutine as the gap the output, when the computer judgment appears when instruction for counter motion, transfers the gap to compensate the subroutine immediately, compensates the pulse after the output to eliminate the reverse gap to carry on again normally inserts makes up the movement. 2. often the value systematic characteristic position error compensates A kind of storehouse by transfers for the designer. Like this in the components design stage, the designer only must input the characteristic the parameter, the system direct production characteristic example model: We must save the related characteristic class in the database the structure information, the database table collection are use in saving this part of related information. According to the characteristic type definition need, we defined the characteristic class code table, the

PLC外文文献翻译

Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. 1.History The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay. In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84

基于PLC相关的毕业设计外文翻译(可编辑修改word版)

毕业论文（设计）外文翻译 题目：可编程逻辑控制器技术 系部名称：信息工程系专业班级： 学生姓名：学号： 指导教师：教师职称： 2014 年3 月XX 日

译文 可编程逻辑控制器技术 引言 PLC（可编程逻辑控制器）实际是一个工业控制系统（近来我们看到更多的是用处理器来取代微控制器），在软件和硬件都配备的条件下，适合应用于工业环境。PLC 的发明是相当必要的，它代替了传统的依靠由继电接触器电路来控制电机。PLC 的工作原理是根据它的输入信号和工作状态来确定输出。用户通常是通过软件或编程输入一个程序，来输出所需要的结果。 如图 8-1 所示，PLC 是由典型的黑色构件组成。特别需要注意的是它的输入和输出， 因为在这些模块上，工业环境会给 CPU 一个输入线，所以很有必要将 CPU 模块隔离以保护其免遭有害的影响。程序单元通常是用计算机来编写程序（一般是梯形图）。 1.1CPU 的中央处理单元 中央处理单元（CPU）是一个 PLC 的主控制器。一般 CPU 本身是一个微控制器。通常这些都是 8 位微控制器，如 8051 ，现在的这些是 16 位和 32 位微控制器。潜规则是，你会发现用在 PLC 控制器上的微控制器多数是由日本生产的日立和富士通，欧洲的西门子控制器，和美国的摩托罗拉微控制器。CPU 也负责通讯，与 PLC 控制器的其它部分相互联系，如程序执行，内存操作，监督输入和设置输出。PLC 控制器拥有复杂的程序用于内存检查，以确保 PLC 内存不被损坏（内存检查是为了安全原因而作出的）。一般来说，CPU 单元多数用来检查 PLC 控制器本身，所以有可能出现的错误很早就会被发现。你可以简单地看任何 PLC 控制器,查看错误信号在发光二极管上的种种指示形式。 1.2内存 系统内存（今天主要是在 FLASH 技术上实现）用于一台 PLC 的过程控制系统。除了 这个操作系统它还包含用户程序将梯形图翻译成二进制的形式。 FLASH 存储器的内容仅在 用户程序改变下可以改变。PLC 控制器较早被用来代替闪存，EPROM 存储器代替了那些只能依靠紫外线灯等擦除内存并依靠程序员来编程的 FLASH 存储器。在 FLASH 技术的作用下这个过程被大大的缩短了。重组程序内存通过程序中的串行通讯用于应用程序开发。使用内存被划分成多个具有特殊功能的模块。存储器某些部分用来存储输入状态和输出状态。一个 输入信号的实际状态是用 1 或0 存储在一个特定的存储位。每一个输入信号和输出信号在内存里都有一个位与之相对应。内存的其他部分用来存储用户程序中使用的变量以及变量的内容。例如，定时器的值和计数器的值都将被存储在这部分内存里。 1.3PLC 控制器的编程 PLC 控制器可以通过计算机（常用的方式）进行编程，还可以通过手动编程器（控制台）编程。这实际上意味着如果你有需要的编程软件那么每个 PLC 控制器都可以通过计算机进行编程。今天的传输计算机是非常适合在工厂对 PLC 控制器进行编程的。这对工业有着非常重要的意义。一旦系统被刷新，重新读取正确的程序到 PLC 就很重要。还可以定期检查 PLC 中的程序是否改变了。这有助于避免在工厂车间发生危险状况（部分汽车制造商建立了通信网络，定期检查项目中的 PLC 控制器，以确保执行的程序是正确的）。

plc外文翻译

1 Bit Logic In structi ons 1.1 Overview of Bit Logic In structi ons 1.1.1 Description Bit logic in structi ons work with two digits, 1 and 0. These two digits form the base of a nu mber system called the binary system. The two digits 1 and 0 are called binary digits or bits. In the world of con tacts and coils, a 1 in dicates activated or en ergized, and a 0 in dicates not activated or not en ergized. The bit logic in struct ions in terpret sig nal states of 1 and 0 and comb ine them accord ing to Boolea n logic. These comb in ati ons produce a result of 1 or 0 that is called the “result of logic operati on ” (RLO). The logic operations that are triggered by the bit logic instructions perform a variety of fun cti ons. There are bit logic in structio ns to perform the followi ng fun cti ons: ---| |--- Normally Ope n Co ntact (Address) ---| / |--- Normally Closed Con tact (Address) ---(SAVE) Save RLO into BR Memory XOR Bit Exclusive OR ---()Output Coil ---(# )--- Midli ne Output ---|NOT|--- In vert Power Flow The followi ng in structio ns react to an RLO of 1: ---(S ) Set Coil ---(R ) Reset Coil SR Set-Reset Flip Flop RS Reset-Set Flip Flop Other in structi ons react to a positive or n egative edge tran siti on to perform the followi ng functions: ---(N)--- Negative RLO Edge Detectio n ---(P)--- Positive RLO Edge Detectio n NEG Address Negative Edge Detectio n POS Address Positive Edge Detectio n

plc外文翻译

1 Bit Logic Instructions 1.1 Overview of Bit Logic Instructions 1.1.1 Description Bit logic instructions work with two digits, 1 and 0. These two digits form the base of a number system called the binary system. The two digits 1 and 0 are called binary digits or bits. In the world of contacts and coils, a 1 indicates activated or energized, and a 0 indicates not activated or not energized. The bit logic instructions interpret signal states of 1 and 0 and combine them according to Boolean logic. These combinations produce a result of 1 or 0 that is called the “result of logic operation” (RLO). The logic operations that are triggered by the bit logic instructions perform a variety of functions. There are bit logic instructions to perform the following functions: ---| |--- Normally Open Contact (Address) ---| / |--- Normally Closed Contact (Address) ---(SAVE) Save RLO into BR Memory XOR Bit Exclusive OR ---( ) Output Coil ---( # )--- Midline Output ---|NOT|--- Invert Power Flow The following instructions react to an RLO of 1: ---( S ) Set Coil ---( R ) Reset Coil SR Set-Reset Flip Flop RS Reset-Set Flip Flop Other instructions react to a positive or negative edge transition to perform the following functions: ---(N)--- Negative RLO Edge Detection ---(P)--- Positive RLO Edge Detection NEG Address Negative Edge Detection POS Address Positive Edge Detection

PLC控制系统外文翻译

附录 Abstract: Programmable controller in the field of industrial control applications, and PLC in the application process, to ensure normal operation should be noted that a series of questions, and give some reasonable suggestions. Key words: PLC Industrial Control Interference Wiring Ground Proposal Description Over the years, programmable logic controller (hereinafter referred to as PLC) from its production to the present, to achieve a connection to the storage logical leap of logic; its function from weak to strong, to achieve a logic control to digital control of progress; its applications from small to large, simple controls to achieve a single device to qualified motion control, process control and distributed control across the various tasks. PLC today in dealing with analog, digital computing, human-machine interface and the network have been a substantial increase in the capacity to become the mainstream of the field of control of industrial control equipment, in all walks of life playing an increasingly important role. ⅡPLC application areas Currently, PLC has been widely used in domestic and foreign steel, petroleum, chemical, power, building materials, machinery manufacturing, automobile, textile, transportation, environmental and cultural entertainment and other industries, the use of mainly divided into the following categories: 1. Binary logic control Replace traditional relay circuit, logic control, sequential control, can be used to control a single device can also be used for multi-cluster control and automation lines. Such as injection molding machine, printing machine, stapler machine, lathe, grinding machines, packaging lines, plating lines and so on. 2. Industrial Process Control In the industrial production process, there are some, such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), PLC using the appropriate A / D and D / A converter module, and a variety of control algorithm program to handle analog, complete closed-loop control. PID closed loop control system adjustment is generally used as a conditioning method was more. Process control in metallurgy, chemical industry, heat treatment, boiler control and so forth have a very wide range of applications 3. Motion Control PLC can be used in a circular motion or linear motion control. Generally use a dedicated motion control module, for example a stepper motor or servo motor driven single-axis or multi-axis position control module, used in a variety of machinery, machine tools, robots, elevators and other occasions. 4. Data Processing PLC with mathematics (including matrix operations, functions, operation, logic operation), data transfer, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing.Data

精品中英文外文翻译--PLC和微处理器-定

Introductions of PLC and MCU A PLC is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs .The user enters a program, usually via software or programmer that gives the desired results. PLC are used in many “real world” applications. If there is industry present, chances are good that there is a PLC present. If you are involved in machining, packaging, material handling, automated assembly or countless other industries, you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has need for PLC. For example, let’s assume that when a switch turns on we want to turn a solenoid on for 5 seconds and then turn it off regardless of how long the switch is on for. We can do this with a simple external timer. What if the process also needed to count how many times the switch individually turned on? We need a lot of external counters. As you can see, the bigger the process the more of a need we have for a PLC. We can simply program the PLC to count its inputs and turn the solenoids on for the specified time. We will take a look at what i s considered to be the “top 20” PLC instructions. It can be safely estimated that with a firm understanding of there instructions one can solve more than 80% of the applications in existence. That‘s right, more than 80%! Of course we’ll learn more than jus t these instructions to help you solve almost ALL your potential PLC applications. The PLC mainly consists of a CPU, memory areas, and appropriate circuits to receive input/output data, as shown in Fig. 19.1 We can actually consider the PLC to be a box full of hundreds or thousands of separate relays, counters, timer and date storage locations. Do these counters, timers, etc. really exist? No, they don’t “physically” exist but rather they are simulated and can be considered software counters, timers, etc. These internal relays are simulated through bit locations in registers. What does each part do? INPUT RELAYS-(contacts) These are connected to the outside world. They physically exist and receive signals from switches, sensors, etc... Typically they are not relays but rather they are transistors.

PLC中英文资料外文翻译-(1)

可编程控制器技术讨论与未来发展 摘自《可编程控制器技术讨论与未来发展》 数字媒体系 08165110 多衡随着时代的发展,当今的技术也日趋完善、竞争愈演愈烈;单靠人工的操作已不能满足于目前的制造业前景,也无法保证更高质量的要求和高新技术企业的形象. 人们在生产实践中看到,自动化给人们带来了极大的便利和产品质量上的保证,同时也减轻了人员的劳动强度,减少了人员上的编制.在许多复杂的生产过程中难以实现的目标控制、整体优化、最佳决策等,熟练的操作工、技术人员或专家、管理者却能够容易判断和操作,可以获得满意的效果.人工智能的研究目标正是利用计算机来实现、模拟这些智能行为,通过人脑与计算机协调工作,以人机结合的模式,为解决十分复杂的问题寻找最佳的途径我们在各种场合看到了继电器连接的控制，那已经是时代的过去，如今的继电器只能作为低端的基层控制模块或者简单的设备中使用到；而PLC的出现也成为了划时代的主题，通过极其稳定的硬件穿插灵活的软件控制，使得自动化走向了新的高潮。 PLC的最大特点在于：电气工程师已不再电气的硬件上花费太多的心计，只要将按钮开关或感应器的输入点连接到PLC的输入点上就能解决问题，通过输出点连接接触器或继电器来控制大功率的启动设备，而小功率的输出设备直接连接就可以。 PLC的内部包含了具有中央处理器的CPU，并带有外部I/O口扩展的I/O接口地址和存储器三大块组成，CPU的核心是由一个或者多个累加器组成，它们具有逻辑的数学运算能力，并能读取程序存储器的内容通过计算后去驱动相应的存储器和I/O接口；I/O口将内部累加器和外部的输入和输出系统连接起来，并将相关的数据存入程序存储器或者数据存储器中；存储器可以将I/O口输入的数据存入存储器中，并在工作时调转到累加器和I/O接口上，存储器分程序存储器ROM和数据存储器RAM,ROM可以将数据永久的存入存储器中，而RAM只能作为CPU计算时临时计算使用的缓冲空间。 PLC的抗干扰是极其优秀的，我们根本不用去关心它的使用寿命和工作场合的恶劣，这些所有的问题已不再成为我们失败的主题，而留给我们的是关心如何来利用PLC的内部资源为我们加强设备的控制能力，使我们的设备更加的柔性。 PLC的语言并不是我们所想象的汇编语言或C语言来进行编程，而是采用原有的继电器控制的梯形图，使得电气工程师在编写程序时很容易就理解了PLC的语言，而且很多的非电气专业人士也对PLC很快认识并深入。

PLC中英文资料外文翻译

可编程控制器 技术讨论与未来发展 学生姓名： ****** 所在院系： ****** 所学专业： ****** 导师姓名： ****** 完成时间：******

外文资料 PLCtechnique discussion and future development With the development of the times, today's technology is maturing, competition intensified。 rely on manual operation does not satisfy the current industry outlook, there is no guarantee of higher quality requirements and high-tech corporate image. People saw in the production practice, automation to bring great convenience and product quality assurance, but also reduce the labor intensity, reducing the staff on the establishment in many complex production process is difficult to achieve target control, the overall optimization, optimal decision-making, skilled operatives, technicians or specialists, managers can easily determine and operate it, you can get satisfactory results. artificial intelligence research is the use of computers to achieve the target, the analog These intelligent behavior, through coordination of the human brain and a computer to combine human models for solving very complex problem of finding the best way. PLC's most important feature is: electrical engineer electrical hardware no longer spend too much scheming, as long as the button switch or sensor input connected to the PLC input point will solve the problem by connecting the output point contacts or relay to control the power of the boot device, and small power output devices can be connected directly. Contained within the PLC having a central processor of the CPU, and with an external I / O port expansion I / O interface and the memory addresses of three major components, CPU core is formed by one or more accumulators, which have the logical math capabilities, and can read the contents of the program memory to drive through the calculation of the corresponding memory and I / O interface。 I / O port to the internal accumulator and external input and output systems together, and the relevant data stored in the program memory or data memory。 memory can be I / O port input data stored in memory and transferred to the accumulator at work, and I / O interfaces, memory sub-ROM program memory and data memory RAM, ROM data can be permanently stored in memory, CPU and RAM only as a temporary calculated using the calculation buffer space. PLC immunity is extremely good, we do not have to care about the life and work of its harsh occasions, all of these issues are no longer the subject of our failure, and left us is concerned with how to take advantage of the PLC's internal resources to

PLC中英文资料外文翻译

附录 外文资料 PLC technique discussion and future development Along with the development of the ages, the technique that is nowadays is also gradually perfect, the competition plays more more strong; the operation that list depends the artificial has already can't satisfied with the current manufacturing industry foreground, also can't guarantee the request of the higher quantity and high new the image of the technique business enterprise. The people see in produce practice, automate brought the tremendous convenience and the product quantities for people up of assurance, also eased the personnel's labor strength, reduce the establishment on the personnel. The target control of the hard realization in many complicated production lines, whole and excellent turn, the best decision etc., well-trained operation work, technical personnel or expert, governor but can judge and operate easily, can acquire the satisfied result. The research target of the artificial intelligence makes use of the calculator exactly to carry out, imitate these intelligences behavior, moderating the work through person's brain and calculators, with the mode that person's machine combine, for resolve the very complicated problem to look for the best path We come in sight of the control that links after the electric appliances in various situation, that is already the that time generation past, now of after use in the mold a perhaps simple equipments of grass-roots control that the electric appliances can do for the low level only;And the PLC emergence also became the epoch-making topic, adding the vivid software control through a very and stable hardware, making the automation head for the new high tide. The PLC biggest characteristics lie in: The electrical engineering teacher already no longer electric hardware up too many calculationses of cost, as long as order the importation that the button switch or the importation of the sensors order to link the PLC up can solve problem, pass to output to order the conjunction contact machine or control the start equipments of the big power after the electric appliances, but the