当前位置：搜档网 › Mesophilic acidification of gelatinaceous wastewater

Mesophilic acidification of gelatinaceous wastewater

Journal of Biotechnology 93(2002)99–108

Mesophilic acidi?cation of gelatinaceous wastewater

Herbert H.P.Fang a,*,Hanqing Yu b

Department of Ci 6il Engineering ,Centre for En 6ironmental Engineering Research ,The Uni 6ersity of Hong Kong ,Pokfulam Road ,

Hong Kong ,China

Department of Applied Chemistry ,Uni 6ersity of Science and Technology of China ,Hefei ,Anhui 230026,China

Received 26April 2001;received in revised form 19June 2001;accepted 31July 2001

Abstract

The in?uence of hydraulic retention time (HRT)and gelatin concentration on the acidi?cation of gelatinaceous wastewater in an up?ow anaerobic reactor was investigated at pH 5.5and 37°C.The degree of gelatin degradation increased with the HRT,from 84.1%at 4h to 89.6%at 24h,but decreased with the increase of the gelatin concentration in the in?uent from 65.2%at 2g-COD l ?1to 51.9%at 30g-COD l ?1.The degradation of gelatin followed the Monod kinetics with a maximum rate of 1.10g (g-VSS·d)?1and a half-rate constant of 0.23g l ?1.The overall production rate of VFA and alcohols decreased with HRT,from 0.33g (g-VSS·d)?1at 4h to 0.15g (g-VSS·d)?1at 24h,but increased with gelatin concentration in the in?uent,from 0.10g (g-VSS·d)?1at 4g-COD l ?1to 0.58g (g-VSS·d)?1at 30g-COD l ?1.The key acidi?cation products were acetate,propionate and butyrate,plus i -butyrate,valerate,i -valerate,caproate and ethanol in smaller quantities.Formate,methanol,propanol and butanol were found only in certain runs.Only 4.5–7.8%of COD in wastewater was converted to hydrogen and methane.The sludge yield was estimated as 0.32090.014g-VSS (g-COD)?1.?2002Elsevier Science B.V.All rights reserved.

Keywords :Acidi?cation;Gelatin;Hydraulic retention time;Protein;Volatile fatty acid

https://www.sodocs.net/doc/ed15126730.html, /locate /jbiotec

strength industrial wastewater.A number of high-rate processes have been successfully com-mercialized in the past decade (Lettinga,1995;Fang and Liu,2000).Most of the full-scale anaer-obic reactors were designed for treating wastewa-ters from the sugar,starch,and brewery industries,the main pollutants of which are car-bohydrates.However,many industrial and agricultural wastewaters also contain apprec-iable quantities of protein.Treating protein-rich

1.Introduction

Since the introduction of the anaerobic ?lter (Young and McCarty,1969),anaerobic processes have become viable for the treatment of high-

*Corresponding author.Tel.:+852-2859-2660;fax:+852-2559-5337.

E -mail address :hrechef@hkucc.hku.hk (H.H.P.Fang).

H.H.P.Fang,H.Yu/Journal of Biotechnology93(2002)99–108 100

wastewater often results in the formation of scum, which accumulates inside the reactor,and causes sludge washout(Lettinga and Hulshoff Pol, 1991).This problem has signi?cantly hindered the application of the anaerobic process to the treat-ment of wastewaters from dairy and slaughter industries.

In addition,proteins are degraded more slowly than carbohydrates.Anaerobic degradation of proteins is a complex process involving various groups of microorganisms.Proteins are?rst hy-drolyzed and degraded by proteolytic enzymes into peptides and individual amino acids(McIner-ney,1988).The peptides and amino acids are then acidi?ed into volatile fatty acids(VFA),hydro-gen,ammonium,and reduced sulfur.The VFA are further converted by acetogens into acetate and H2/CO2,both of which are lastly converted to methane by methanogens.The initial hydrolysis is the rate-limiting step in protein degradation(Gu-jer and Zehnder,1983),and the overall degrada-tion rate is slow(Harper and Pohland,1986; McInerney,1988).

To improve the process ef?ciency,a two-stage anaerobic process(Pohland and Ghosh,1971)has been developed for the treatment of protein-rich wastewaters.In such a process,hydrolysis and acidi?cation are carried out in the?rst reactor, the ef?uent of which is subsequently further treated in the second reactor for acetogenesis and methane production.Gelatin,a protein rich in animal connective tissue,is the main constituent in slaughterhouse and meat-processing wastewa-ters.Acidogenesis of gelatin in a continuously stirred tank reactor(CSTR)has been studied (Breure and van Andel,1984).Results show that pH is crucial to the acidogenesis ef?ciency and product distribution.Furthermore,gelatin hydrol-ysis was found to be suppressed by the presence of glucose,because the latter is the preferred substrate for the hydrolytic bacteria(Breure et al., 1986).However,little information is available on the acidogenesis of gelatin in wastewaters in con-tinuously fed up?ow reactors.This work was thus conducted to investigate the effects of hydraulic retention time(HRT)and gelatin concentration in wastewater on the acidi?cation of gelatin in a mesophilic up?ow anaerobic reactor.2.Materials and methods

2.1.Reactor and wastewater

The continuous experiment was conducted for 412days in a2.8l up?ow reactor(84mm inside diameter and500mm height)used previously for methanogenic anaerobic degradation(Fang et al., 1994).The reactor was water-jacketed and oper-ated at37°C.Synthetic wastewater was prepared by using gelatin as the sole carbon source,plus balanced nutrient and trace metals,following the formulation used in the previous study(Fang et al.,1994).Throughout the experiment,the pH of the mixed liquor was kept at5.590.1in order to suppress methanogenesis.The reactor was seeded with the sludge taken from a conventional methanogenic reactor treating dairy wastewater for a previous study(Fang and Chung,1999).The initial sludge concentration was10.8g l?1of volatile suspended solids(VSS).The sludge reten-tion was controlled at15days,by wasting one-?fteenth of the sludge in the reactor daily.

This study was conducted in two phases:in phase I,the in?uent COD(chemical oxygen de-mand)was kept at4g l?1,while the HRT was decreased stepwise from the initial24h to16,12, 8,6,and lastly4h;in phase II,the HRT was kept at12h,while the wastewater COD was increased stepwise from2g l?1to9,15,20,and lastly30 g l?1.The reactor was operated at each HRT or COD level for33–44days to ensure reaching steady state before changing the HRT or COD to the next level.

2.2.Analysis

The production of biogas was measured daily by the water displacement method.The contents of H2,CH4,CO2and N2in the biogas were analyzed by a gas chromatograph(Hewlett–Pack-ard,Model5890Series II)equipped with a ther-mal conductivity detector and a2m×2mm (inside diameter)stainless-steel column packed with Porapak N(80–100mesh).Injector and detector temperatures were kept at130and 200°C,respectively,while column temperature was increased from90to110°C.

H .H .P .Fang ,H .Yu /Journal of Biotechnology 93(2002)99–108101

The concentrations of individual acidogenic products in the ef ?uent were determined by a second gas chromatograph of same model equipped with a ?ame ionization detector and a 10m ×0.53mm HP-FFAP fused-silica capillary.The products were mostly VFA,including acetate,propionate,butyrate,i -butyrate,valerate,i -valer-ate,caproate and lactate,and alcohols,including methanol,ethanol,propanol and butanol.Ef ?uent samples were ?ltered through a 0.2m m membrane,acidi ?ed by formic acid,and mea-sured for free acids.The temperature of the column was initially 70°C for 4min,followed by 140°C for 3min,and lastly 170°C for 4min.The temperatures of injector and detector were both 200°C.Helium was used as the carrier gas at a ?ow rate of 25ml min ?1.The detectable levels were 1mg l ?1for individual VFA (from C2to C7)and 3mg l ?1for individual alcohols.The formate concentration was measured by the col-orimetric method (Lang and Lang,1972).Protein was measured by the Lowry –Folin method (Lowry et al.,1951).

Measurements of COD,pH,NH 3-N,and VSS were performed according to the Standard Meth-ods (APHA,AWWA and WEF,1992).

3.Results and discussion

3.1.O 6erall performance

During anaerobic degradation,gelatin was con-verted into VFA and alcohols in the ef ?uent,plus H 2/CO 2in the biogas and biomass.Fig.1illus-trates:(a)HRT;(b)gelatin concentration in in ?u-ent;(c)gelatin concentration in ef ?uent;(d)total VFA and alcohol concentration in ef ?uent;and (e)biogas production rate throughout this study.Results in Fig.1c illustrate that over 84.1%of 4g-COD l ?1of gelatin in the wastewater was de-graded for HRT as low as 4h,and over 89.6%of gelatin up to 30g-COD l ?1in wastewater was degraded at 12h of HRT.Fig.1d illustrates that the ef ?uent VFA /alcohol concentration increased with both HRT and in ?uent gelatin concentra-tion.On treating wastewater containing 4g-COD l ?1of gelatin,the ef ?uent VFA /alcohol

concentration decreased from 1.67g l ?1at 24h of HRT to 0.96g l ?1at 4h of HRT;at 12h of HRT,the ef ?uent VFA /alcohol concentration in-creased from 0.76g l ?1at 2g l ?1of gelatin in wastewater to 7.76g l ?1at 30g-COD l ?1.

Fig.1e illustrates that the total biogas produc-tion rate increased with gelatin concentration in wastewater,but decreased when HRT https://www.sodocs.net/doc/ed15126730.html,pared to the conventional methanogenic pro-cess,the acidogenic process produces a much lower amount of gas due to the suppression of methane production.For example,in a previous

Fig.1.Operational conditions and performance of the acidi ?-cation reactor:(a)HRT;(b)gelatin concentration in in ?uent;(c)gelatin concentration in ef ?uent;(d)total VFA /alcohol concentration in ef ?uent;and (e)biogas production rate.

H .H .P .Fang ,H .Yu /Journal of Biotechnology 93(2002)99–108

102Fig.2.Effect of HRT on:(a)degradation ef ?ciency;and (b)speci ?c gelatin degradation rate.

this study were considerably lower than the value 3.653g (g-VSS ·d)?1found in another study treat-ing gelatin at pH 5.3,4h of HRT and 3.04g l ?1of gelatin in a complete-mix reactor (Breure and van Andel,1984).The lower rates of this study are likely due to the lack of mixing in the up ?ow reactor.However,the rates found in this study were still considerably higher than the protein degradation rate of 0.172g (g-VSS ·d)?1in the acidogenesis of a dairy wastewater using a similar up ?ow reactor (Yu and Fang,2000).This is due to the absence of carbohydrate in the wastewater of this study.Carbohydrates tend to suppress the synthesis of exopeptidases,a group of enzymes facilitating protein hydrolysis (McInerney,1988);their presence in dairy wastewater lowers the protein degradation rate.

The results of Figs.2a and 3a show that gelatin degradation ef ?ciency had a near-linear relation-ship with both HRT and gelatin concentration in wastewater.Based on linear regression analysis,it can be expressed as follows:

ef ?ciency =2.37×HRT ?0.63×S i +47.05r =0.947

(1)

where S i represents the gelatin concentration in wastewater.Eq.(1)shows that gelatin degrada-tion is more dependent on HRT (h)than S i (g l ?1).Therefore,longer HRT is required to increase the gelatin degradation ef ?ciency.

study on mesophilic methanogenesis of proteina-ceous wastewater using the same reactor (Fang et al.,1994),the gas production reached 16.70l (l ·d)?1at 10h of HRT and 10g l ?1of protein in wastewater,whereas the gas production of this acidogenic reactor was only 5.60l (l ·d)?1at 12h of HRT and 15g l ?1of protein in wastewater.

3.2.Gelatin degradation

In anaerobic degradation,gelatin is ?rst hy-drolyzed,and the products of this reaction are further fermented into acids and alcohols.It was found in this study that,gelatin degradation ef ?-ciency increased with HRT,from 84.1%at 4h to 94.3%at 24h (Fig.2a),but decreased with the increase of gelatin concentration in wastewater,from 98.9%at 2g-COD l ?1to 89.6%at 30g-COD l ?1(Fig.3a).The degradation ef ?ciency ranging from 84.1to 98.6%indicates that gelatin was easily hydrolyzed under acidogenic conditions.

Fig.2b illustrates that the speci ?c gelatin degra-dation rate treating 4g-COD l ?1of gelatin de-creased with the increase of HRT,from 0.85g (g-VSS ·d)?1at 4h to 0.25g (g-VSS ·d)?1at 24h.Fig.3b,on the other hand,illustrates that the speci ?c gelatin degradation rate at 12h of HRT increased with gelatin concentration in wastewa-ter,from 0.19g (g-VSS ·d)?1at 2g-COD l ?1to 1.49g (g-VSS ·d)?1at 30g-COD l ?1.The rates in

Fig.3.Effect of gelatin concentration in wastewater on:(a)degradation ef ?ciency;and (b)speci ?c gelatin degradation rate.

H .H .P .Fang ,H .Yu /Journal of Biotechnology 93(2002)99–108103

Fig.4.Gelatin degradation kinetics.

gelatin.In another study on acidi ?cation of gelatin using a complete-mix reactor (Breure and van Andel,1984),the R max and K values were estimated as 0.29g (g-VSS ·d)?1and 3.43g l ?1,respectively.The R max value is substantially lower than that in the present study.This could be due to the differences in reactor con ?guration and operational conditions.In the up ?ow reactor of the present study,the gelatin concentration de-creased as the wastewater ?owed upward,and the gelatin concentration in the ef ?uent was substan-tially lower than the average concentration in the reactor;but in a complete-mix reactor,the gelatin concentration in the ef ?uent equals that in the mixed liquor.

3.4.Production and distribution of VFA and alcohols

Acidi ?cation of gelatin produced not just VFA but also alcohols.Fig.5a illustrates that the over-all production rate of VFA and alcohols de-creased with HRT,from 0.33g (g-VSS ·d)?1at 4h to 0.15g (g-VSS ·d)?1at 24h.Fig.5b,on the other hand,illustrates that the production rate increased with gelatin concentration in wastewa-ter,from 0.10g (g-VSS ·d)?1at 4g-COD l ?1to 0.58g (g-VSS ·d)?1at 30g-COD l ?1.

Tables 1and 2summarize,respectively,the data of total VFA /alcohols concentration in the

3.3.Gelatin degradation kinetics

At steady state,the mass balance of gelatin in the acidogenic reactor may be expressed,assum-ing that the ef ?uent and waste gelatin concentra-tions are equal,as follows:RM =QS i ?(Q ?Q w )S e ?Q w S e (2)

R =Q (S i ?S e )/M

(3)

where Q and Q w are the ?ow rates (l d ?1)of ef ?uent and waste sludge,respectively;S i and S e are the in ?uent and ef ?uent gelatin concentrations (g l ?1),respectively;R is the speci ?c gelatin degradation rate (g (g-VSS ·d)?1);M is the total biomass (g-VSS).The gelatin degradation rate may follow the Monod model as:R =R max S e /(K s +S e )

(4)where R max is the maximum gelatin degradation rate (g (g-VSS ·d)?1);S e is the ef ?uent gelatin concentration (g l ?1);and K s is the half-rate con-centration (g l ?1).To best-?t the degradation data,R max and K s were determined as:R max =1.10g (g-VSS ·d)?1K s =0.23g l ?1

Fig.4illustrates that the degradation rates cal-culated from Eq.(4)using the aforementioned parameters ?t the measured data satisfactorily.In a recent study on acidi ?cation of lactose using a similar up ?ow reactor and operational conditions (Fang and Yu,2001),the R max and K values were found to be 4.39g (g-VSS ·d)?1and 1.97g l ?1,respectively.This suggests that acidi ?cation rate of lactose was signi ?cantly higher than that of

Fig.5.Speci ?c VFA /alcohol production rate at various:(a)HRTs;and (b)gelatin concentrations.

H .H .P .Fang ,H .Yu /Journal of Biotechnology 93(2002)99–108105

Fig.6.Ef ?uent propionate concentration at various gelatin concentrations.

production of propionate might only be achieved when less dilute substrate concentration is used.Tables 1and 2also show that production of alcohols was much lower than that of VFA.Etha-nol was the main alcohol produced,accounting for only 2–6%of total VFA /alcohols.Methanol was produced only in certain runs,and never exceeded 2.5%.Propanol and butanol were not detected when gelatin concentration was at 4–8g-COD l ?1.However,at 15g-COD l ?1and higher concentrations,propanol was produced.The proportions of propanol and butanol in-creased with gelatin concentration,but were inde-pendent of HRT.In the acidogenic reactors treating carbohydrate-rich wastewaters,alcohol concentrations could sometimes exceed those of VFA,especially when hydrogen partial pressure is higher than 30kPa (Dabrock et al.,1992;Jones and Woods,1986).However,results of this study show that acidi ?cation of gelatin produced mostly VFA and substantially lower amount of alcohols,as observed previously by others (Breure and van Andel,1984;Jain and Zeikus,1989).

3.5.Ammonium production

Ammonium was produced during the acidi ?ca-tion of protein.As shown in Table 3,the ef ?uent ammonium concentration increased with gelatin concentration,but decreased with the increase of HRT,as expected from the gelatin degradation patterns.The ammonium concentration in the ef ?uent ranged from 0.23to 2.50g l ?1,which is substantially below the threshold level of 5g l ?1above which it becomes toxic to acidogens (Breure and van Andel,1984;Koster and Let-tinga,1988).Thus,the production of ammonium

ef ?uent plus percentages of individual VFA and alcohols at various HRT and gelatin concentra-tions in wastewater.It shows that acetate was the main acidi ?cation product,accounting for 17.8–35.1%of total VFA /alcohols,with an average of 27.4%.The next important VFAs were propi-onate,butyrate and i -butyrate ranging from 10.6to 20.3%,9.0to 15.0%and 10.6to 14.7%,respec-tively.Valerate,i -valerate and caproate and etha-nol were found at lower percentages.Formate,methanol,propanol and butanol were found only in certain runs,at less than 5%,whereas lactate was not detected in all runs.

The product distribution was dependent upon the operational parameters.For instance,the ace-tate concentration increased with both HRT and gelatin concentration in wastewater;but by con-trast,the concentration of propionate in the ef ?uent was independent of HRT,but increased with the gelatin concentration,as illustrated in Fig.6.Since the methanogenesis of propionate is slower compared with acetate and butyrate,pro-pionate was an undesirable intermediate product in the two-stage anaerobic process (Cohen et al.,1984;Harper and Pohland,1986).The engineer-ing implication of this observation is that low

Table 3

Ef ?uent ammonia concentrations at various HRTs and gelatin concentrations in wastewater HRT (h)NH 3-N (g l ?1)Gelatin in wastewater (g-COD l ?1)NH 3-N (g l ?1)40.29590.01520.23390.0170.34990.0260.42490.031460.38690.028890.96490.0570.42490.03112 1.44390.078150.40990.0301620 1.79190.0950.44890.037

2.50190.106

H .H .P .Fang ,H .Yu /Journal of Biotechnology 93(2002)99–108

106Fig.7.Partial pressures of hydrogen,methane and carbon dioxide at various:(a)HRTs;and (b)gelatin concentrations.

detectable at 16h.Fig.7b illustrates that on treating gelatinaceous wastewater at 12h of HRT,the hydrogen partial pressure increased with gelatin concentration,from undetectable at 2g-COD l ?1to 10kPa at 30g-COD l ?1.The meth-ane partial pressure followed an opposite trend to that of hydrogen,while carbon dioxide partial pressure was steady,ranging from 50to 69kPa.The total COD of hydrogen and methane ac-counted for only 4.5–7.8%of COD in wastewa-ter.It increased with HRT,but decreased with the increase of gelatin concentration.The COD con-version to hydrogen and methane in acidi ?cation was considerably lower than the 86–90%found in a methanogenic reactor treating proteinaceous wastewater (Fang and Chung,1999).3.7.Sludge yield

Sludge yield in an anaerobic treatment system can be estimated based on COD balance (Fang et al.,1994).COD is a wastewater parameter indi-rectly measuring the amount of electrons that are available for oxidation.In a strict anaerobic pro-cess,no electron acceptor is added to the system.In such a case,although the COD in the in ?uent is transformed into VFA,alcohols,hydrogen,methane and biomass,the overall COD should remain unchanged.As a result,the COD differ-ence between in ?uent and ef ?uent should be equal to the COD in biogas,i.e.hydrogen and methane,and COD in the biomass.The biomass COD can,thus,be estimated from the other three terms of COD,all of which can be accurately measured.Assuming the chemical formula of sludge to be C 5H 7NO 2,each gram of biomass is equivalent to 1.42g of COD,and the sludge yield can be estimated accordingly.

appears to have no in ?uence on the acidi ?cation of gelatin in this study.This is also due to the acidic condition in the acidogenic reactor,under which little ammonium is converted to the more toxic form of ammonia.

However,methanogens are more vulnerable to the ammonia toxicity and the increase of pH in the methanogenic reactor would convert ammo-nium into toxic ammonia.Thus,controlling the ammonium concentration could be critical in feeding the acidi ?ed ef ?uent to the methanogenic reactor in the two-stage process.

3.6.Gas production

Fig.7a illustrates that on treating gelatin at 4g-COD l ?1,the hydrogen partial pressure de-creased with the increase of HRT,becoming un-

Table 4

Sludge yields at various HRTs and gelatin concentrations in wastewater HRT (h)Yield (g-VSS (g-COD)?1)Gelatin in wastewater (g-COD l ?1)Yield (g-VSS (g-COD)?1)0.32690.015420.31190.01840.32390.02060.31690.0200.32390.008890.32090.007120.32290.018150.31690.0120.31090.00716200.33090.0210.30190.011

0.33890.013

H.H.P.Fang,H.Yu/Journal of Biotechnology93(2002)99–108107

Table4summarizes the estimated yield of gelatin-acidifying sludge at various HRTs and gelatin concentrations.The average yield was 0.32090.014g-VSS(g-COD)?1,which is com-parable to that of acidogenic sludge reported in literature ranging from0.230to0.324g-VSS(g-COD)?1(Cohen et al.,1980;Zoetemeyer et al., 1982;Kissalita et al.,1989;Fang and Yu,2001; Yu and Fang,2000).

4.Conclusions

At pH 5.5and37°C,the degree of gelatin degradation increased with the HRT,from84.1% at4h to89.6%at24h,but decreased with the increase of the gelatin concentration in the in?u-ent from65.2%at2g-COD l?1to51.9%at30 g-COD l?1.The degradation of gelatin followed the Monod kinetics with a maximum rate of1.10 g(g-VSS·d)?1and a half-rate constant of0.23 g l?1.The overall production rate of VFA and alcohols decreased with HRT,from0.33g(g-VSS·d)?1at4h to0.15g(g-VSS·d)?1at24h, but increased with gelatin concentration in in?u-ent,from0.10g(g-VSS·d)?1at4g-COD l?1to 0.58g(g-VSS·d)?1at30g-COD l?1.The key acidi?cation products were acetate,propionate and butyrate.Only4.5–7.8%of COD in wastewa-ter was converted to hydrogen and methane.The sludge yield was estimated as0.32090.014g-VSS (g-COD)?1.

Acknowledgements

The authors wish to thank the Hong Kong Research Grants Council for the support of this study(HKU7004/98E),and H.H.P.F.wishes to thank the Croucher Foundation for the Senior Research Fellowship.

References

APHA,AWWA and WEF,1992.Standard Methods for the Examination of Water and Wastewater,18th ed.American Public Health Association,Washington D.C.Breure, A.M.,van Andel,J.G.,1984.Hydrolysis and acidogenic fermentation of a protein,gelatin,in an anaero-bic continuous culture.Appl.Microbiol.Biotechnol.20, 45–49.

Breure, A.M.,Mooijman,K.A.,van Andel,J.G.,1986.

Protein degradation in anaerobic digestion:in?uence of volatile fatty acids and carbohydrates on hydrolysis and acidogenic fermentation of gelatin.Appl.Microbiol.Bio-technol.24,426–431.

Cohen,A.,Breure,A.M.,van Andel,J.G.,van Deursen,A., 1980.In?uence of phase separation on the anaerobic diges-tion of glucose-I maximum COD-turnover rate during continuous operation.Water Res.14,1439–1448. Cohen,A.,van Gemert,J.M.,Zoetemeyer,R.J.,Breure,A.M., 1984.Main characteristics and stoichiometric aspects of acidogenesis of soluble carbohydrate containing wastewa-ter.Process Biochem.19,228–232.

Dabrock, B.,Bahl,H.,Gottschalk,G.,1992.Parameters affecting solvent production by Clostridium pasteurinum.

Appl.Environ.Microbiol.58,1233–1239.

Fang,H.H.P.,Chui,H.K.,Li,Y.Y.,Chen,T.,1994.Perfor-mance and granular characteristics of UASB process treat-ing wastewater with hydrolyzed proteins.Water Sci.

Technol.30,55–63.

Fang,H.H.P.,Chung,D.W.C.,1999.Anaerobic treatment of proteinaceous wastewater under mesophilic and ther-mophilic conditions.Water Sci.Technol.40,77–84. Fang,H.H.P.,Liu,Y.,2000.Anaerobic wastewater treatment in(sub-)tropical regions.Proceedings of International Symposium of the COE Project on Establishment and Evaluation of Advanced Water Treatment Technology Systems Using Functions of Complex Microbial Commu-nity.March,Tokyo,pp.119–130.

Fang,H.H.P.,Yu,H.Q.,2001.Acidi?cation of lactose in wastewater.J.Environ.Eng.127(9),825–831.

Gujer,W.,Zehnder, A.J.B.,1983.Conversion processes in anaerobic digestion.Water Sci.Technol.15,127. Harper,S.R.,Pohland,F.G.,1986.Recent developments in hydrogen management during anaerobic biological wastewater treatment.Biotechnol.Bioeng.28,585–602. Jain,M.K.,Zeikus,J.G.,1989.Bioconversion of gelatin to methane by a coculture of Clostridium collageno6orans and Methanosarcina barkeri.Appl.Environ.Microbiol.55, 366–371.

Jones,D.T.,Woods,D.R.,1986.Acetone–butanol fermenta-tion revisited.Microbiol.Rev.50,484–524.

Kissalita,W.S.,Lo,K.V.,Pinder,K.L.,1989.Kinetics of whey–lactose acidogenesis.Biotechnol.Bioeng.33,623–630.

Koster,I.W.,Lettinga,G.,1988.Anaerobic digestion at ex-treme ammonia concentration.Agric.Wastes9,51–62. Lang,E.,Lang,H.,1972.Spezi?sche farbreaktion zum di-recten nachweis der ameisensure.Zeitschrift fur Analytis-che Chimie260,8–10.

Lettinga,G.,1995.Anaerobic digestion and wastewater treat-ment systems.Antonie van Leeuwenhoek67,3–28.

H.H.P.Fang,H.Yu/Journal of Biotechnology93(2002)99–108 108

Lettinga,G.,Hulshoff Pol,L.W.,1991.UASB-process design for various types of wastewaters.Water Sci.Technol.24, 87–107.

Lowry,O.H.,Rosebrough,N.J.,Farr,A.L.,Randall,R.J., 1951.Protein measurement with the Folin phenol reagent.

J.Biol.Chem.193,265–275.

McInerney,M.J.,1988.Anaerobic hydrolysis and fermenta-tion of fats and proteins.In:Zehnder,A.J.B.(Ed.),Biol-ogy of Anaerobic Microorganisms.Wiley,New York,pp.

373–416.

Pohland,F.G.,Ghosh,S.,1971.Developments in anaerobic stabilization of organic wastes,the two-phase concept.

Environ.Technol.1,255–266.Young,J.C.,McCarty,P.L.,1969.The anaerobic?lter for waste treatment.J.Water Pollut.Control Fed.41,R160–R173.

Yu,H.Q.,Fang,H.H.P.,2000.Thermophilic acidi?cation of dairy wastewater.Appl.Microbiol.Biotechnol.54,439–444.

Zoetemeyer,R.J.,Arnoldy,P.,Cohen,A.,Boelhouwer,C., 1982.In?uence of temperature on the anaerobic acidi?ca-tion of glucose in a mixed culture forming part of a two-stage digestion process.Water Res.16,313–321.

如何写先进个人事迹

如何写先进个人事迹篇一：如何写先进事迹材料如何写先进事迹材料一般有两种情况：一是先进个人，如先进工作者、优秀党员、劳动模范等；一是先进集体或先进单位，如先进党支部、先进车间或科室，抗洪抢险先进集体等。无论是先进个人还是先进集体，他们的先进事迹，内容各不相同，因此要整理材料，不可能固定一个模式。一般来说，可大体从以下方面进行整理。 (1)要拟定恰当的标题。先进事迹材料的标题，有两部分内容必不可少，一是要写明先进个人姓名和先进集体的名称，使人一眼便看出是哪个人或哪个集体、哪个单位的先进事迹。二是要概括标明先进事迹的主要内容或材料的用途。例如《王鬃同志端正党风的先进事迹》、《关于评选张鬃同志为全国新长征突击手的材料》、《关于评选鬃处党支部为省直机关先进党支部的材料》等。 (2)正文。正文的开头，要写明先进个人的简要情况，包括：姓名、性别、年龄、工作单位、职务、是否党团员等。此外，还要写明有关单位准备授予他(她)什么荣誉称号，或给予哪种形式的奖励。对先进集体、先进单位，要根据其先进事迹的主要内容，寥寥数语即应写明，不须用更多的文字。然后，要写先进人物或先进集体的主要事迹。这部分内容是全篇材料

的主体，要下功夫写好，关键是要写得既具体，又不繁琐；既概括，又不抽象；既生动形象，又很实在。总之，就是要写得很有说服力，让人一看便可得出够得上先进的结论。比如，写一位端正党风先进人物的事迹材料，就应当着重写这位同志在发扬党的优良传统和作风方面都有哪些突出的先进事迹，在同不正之风作斗争中有哪些突出的表现。又如，写一位搞改革的先进人物的事迹材料，就应当着力写这位同志是从哪些方面进行改革的，已经取得了哪些突出的成果，特别是改革前后的．经济效益或社会效益都有了哪些明显的变化。在写这些先进事迹时，无论是先进个人还是先进集体的，都应选取那些具有代表性的具体事实来说明。必要时还可运用一些数字，以增强先进事迹材料的说服力。为了使先进事迹的内容眉目清晰、更加条理化，在文字表述上还可分成若干自然段来写，特别是对那些涉及较多方面的先进事迹材料，采取这种写法尤为必要。如果将各方面内容材料都混在一起，是不易写明的。在分段写时，最好在每段之前根据内容标出小标题，或以明确的观点加以概括，使标题或观点与内容浑然一体。最后，是先进事迹材料的署名。一般说，整理先进个人和先进集体的材料，都是以本级组织或上级组织的名义；是代表组织意见的。因此，材料整理完后，应经有关领导同志审定，以相应一级组织正式署名上报。这类材料不宜以个人名义署名。写作典型经验材料-般包括以下几部分： (1)标题。有多种写法，通常是把典型经验高度集中地概括出来，一

明胶制作方法及工艺流程

明胶制作方法及工艺流程明胶制作方法及工艺流程明胶制法明胶是动物的皮、骨、白色结缔组织中含有的胶原蛋白，经提纯和初级水解后加工而制得的一种产品。明胶为淡黄至黄色，半透明微带光泽的粉粒或薄片，无特殊臭味，无挥发性。一般明胶含水在16%以下，在干燥环境明胶比较稳定，在潮湿环境下易吸潮被细菌分解而变质。明胶在灼烧时，变软胀大直至炭化，放出一种特殊的角燃烧羽毛或氨的臭味。在冷水中明胶难溶解，但能吸水而变软，而在热水中极易溶解。明胶难溶于汽油、乙醇、氯仿等普通有机溶剂。但可溶于醋酸、水杨酸和苯二甲酸等有机酸，还可溶于尿素、硫脲及溴化钾、碘化钾等水溶液中。明胶是一种高分子化合物，其分子量约为17500－450000。明胶的用途：按用途可分为照相明胶、食用明胶和工业明胶。它广泛应用于食品、医药、化工、纺织、印染、造纸、火柴、五金、家具以及感光材料等从多行业之中。 1、食品工业：用于妈糖、点心、罐头、冰淇淋、汽水、布丁等。 2、医药工业：用于外科敷料、调制丸剂、药膏、制胶囊、制药丸的糖衣层、鱼肝油丸的外皮。 3、感光材料：用于制造照相、电影胶片、X光片、印相纸、放大纸等。 4、印刷工业：用于照相制版和高合印刷胶等。 5、轻纺工业：用于丝绸、棉布、毛毯、纸、皮革制品、草鞋编织品的上浆上光等。 6、化学工业：用于塑料、橡胶、乐器、铅笔、木材、书籍等。 7、粘合剂：用于砂布、砂轮、模型、乐器、铅笔、木材、书籍等。主要原料：制取明磁的主要原料是猪、牛、羊等动物的皮，包括鲜皮和干皮。皮产主要来自两方面。第理制革厂制革时割下的边角皮，零碎破以及不适合制革的皮；第二是肉类加工厂、食品厂剥下的鲜猪皮。皮料种类、性状及用途种类性状用途鲜皮类、牛皮、上剖皮：制革厂机械剖下的牛皮中心层，两面光洁不带皮下层。下剖皮：一面光洁，一面略带皮下层。制上等明胶、制一般明胶。牛块皮：制革厂不用的牛头，脚皮和边角零料皮，制上等明胶。重鲜皮：制底革时剖下来的碎牛皮，制工业明胶。猪剖皮：制猪革时剖下的两面光洁的皮。制上等明胶。鲜猪皮：肉类加工厂和食品厂供应的新鲜、冷藏猪皮，制上等明胶。鲜羊皮：制羊革时剖下的碎皮，制一般明胶。鲜杂皮：制其它革时丢弃的皮，如马、驴皮、制皮胶。

关于时间管理的英语作文 manage time

How to manage time Time treats everyone fairly that we all have 24 hours per day. Some of us are capable to make good use of time while some find it hard to do so. Knowing how to manage them is essential in our life. Take myself as an example. When I was still a senior high student, I was fully occupied with my studies. Therefore, I hardly had spare time to have fun or develop my hobbies. But things were changed after I entered university. I got more free time than ever before. But ironically, I found it difficult to adjust this kind of brand-new school life and there was no such thing called time management on my mind. It was not until the second year that I realized I had wasted my whole year doing nothing. I could have taken up a Spanish course. I could have read ten books about the stories of successful people. I could have applied for a part-time job to earn some working experiences. B ut I didn’t spend my time on any of them. I felt guilty whenever I looked back to the moments that I just sat around doing nothing. It’s said that better late than never. At least I had the consciousness that I should stop wasting my time. Making up my mind is the first step for me to learn to manage my time. Next, I wrote a timetable, setting some targets that I had to finish each day. For instance, on Monday, I must read two pieces of news and review all the lessons that I have learnt on that day. By the way, the daily plan that I made was flexible. If there’s something unexpected that I had to finish first, I would reduce the time for resting or delay my target to the next day. Also, I would try to achieve those targets ahead of time that I planed so that I could reserve some more time to relax or do something out of my plan. At the beginning, it’s kind of difficult to s tick to the plan. But as time went by, having a plan for time in advance became a part of my life. At the same time, I gradually became a well-organized person. Now I’ve grasped the time management skill and I’m able to use my time efficiently.

英语演讲稿：未来的工作

英语演讲稿：未来的工作这篇《英语演讲稿范文：未来的工作》，是特地，希望对大家有所帮助！热门演讲推荐：竞聘演讲稿 | 国旗下演讲稿 | 英语演讲稿 | 师德师风演讲稿 | 年会主持词 | 领导致辞 everybody good afternoon:. first of all thank the teacher gave me a story in my own future ideal job. everyone has a dream job. my dream is to bee a boss, own a pany. in order to achieve my dreams, i need to find a good job, to accumulate some experience and wealth, it is the necessary things of course, in the school good achievement and rich knowledge is also very important. good achievement and rich experience can let me work to make the right choice, have more opportunities and achievements. at the same time, munication is very important, because it determines whether my pany has a good future development. so i need to exercise their municative ability. i need to use all of the free time to learn

关于坚持的英语演讲稿

关于坚持的英语演讲稿 Results are not important, but they can persist for many years as a commemoration of. Many years ago, as a result of habits and overeating formed one of obesity, as well as indicators of overall physical disorders, so that affects my work and life. In friends to encourage and supervise, the participated in the team Now considered to have been more than three years, neither the fine rain, regardless of winter heat, a day out with 5:00 time. The beginning, have been discouraged, suffering, and disappointment, but in the end of the urging of friends, to re-get up, stand on the playground. 成绩并不重要，但可以作为坚持多年晨跑的一个纪念。多年前，由于庸懒习惯和暴饮暴食，形成了一身的肥胖，以及体检指标的全盘失常，以致于影响到了我的工作和生活。在好友的鼓励和督促下，参加了晨跑队伍。现在算来，已经三年多了，无论天晴下雨，不管寒冬酷暑，每天五点准时起来出门晨跑。开始时，也曾气馁过、痛苦过、失望过，但最后都在好友们的催促下，重新爬起来，站到了操场上。 In fact, I did not build big, nor strong muscles, not a sport-born people. Over the past few years to adhere to it, because I have a team behind, the strength of a strongteam here, very grateful to our team, for a long time, we encourage each other, and with sweat, enjoying common health happy. For example, Friends of the several run in order to maintain order and unable to attend the 10，000 meters race, and they are always concerned about the brothers and promptly inform the place and time, gives us confidence and courage. At the same time, also came on their own inner desire and pursuit for a good health, who wrote many of their own log in order to refuel for their own, and inspiring. 其实我没有高大身材，也没健壮肌肉，天生不属于运动型的人。几年来能够坚持下来，因为我的背后有一个团队，有着强大团队的力量，在这里，非常感谢我们的晨跑队，长期以来，我们相互鼓励着，一起流汗，共同享受着健康带来的快

关于管理的英语演讲

1.How to build a business that lasts100years 0:11Imagine that you are a product designer.And you've designed a product,a new type of product,called the human immune system.You're pitching this product to a skeptical,strictly no-nonsense manager.Let's call him Bob.I think we all know at least one Bob,right?How would that go? 0:34Bob,I've got this incredible idea for a completely new type of personal health product.It's called the human immune system.I can see from your face that you're having some problems with this.Don't worry.I know it's very complicated.I don't want to take you through the gory details,I just want to tell you about some of the amazing features of this product.First of all,it cleverly uses redundancy by having millions of copies of each component--leukocytes,white blood cells--before they're actually needed,to create a massive buffer against the unexpected.And it cleverly leverages diversity by having not just leukocytes but B cells,T cells,natural killer cells,antibodies.The components don't really matter.The point is that together,this diversity of different approaches can cope with more or less anything that evolution has been able to throw up.And the design is completely modular.You have the surface barrier of the human skin,you have the very rapidly reacting innate immune system and then you have the highly targeted adaptive immune system.The point is,that if one system fails,another can take over,creating a virtually foolproof system. 1:54I can see I'm losing you,Bob,but stay with me,because here is the really killer feature.The product is completely adaptive.It's able to actually develop targeted antibodies to threats that it's never even met before.It actually also does this with incredible prudence,detecting and reacting to every tiny threat,and furthermore, remembering every previous threat,in case they are ever encountered again.What I'm pitching you today is actually not a stand-alone product.The product is embedded in the larger system of the human body,and it works in complete harmony with that system,to create this unprecedented level of biological protection.So Bob,just tell me honestly,what do you think of my product? 2:47And Bob may say something like,I sincerely appreciate the effort and passion that have gone into your presentation,blah blah blah-- 2:56(Laughter) 2:58But honestly,it's total nonsense.You seem to be saying that the key selling points of your product are that it is inefficient and complex.Didn't they teach you 80-20?And furthermore,you're saying that this product is siloed.It overreacts, makes things up as it goes along and is actually designed for somebody else's benefit. I'm sorry to break it to you,but I don't think this one is a winner.

关于工作的优秀英语演讲稿

关于工作的优秀英语演讲稿 Different people have various ambitions. Some want to be engineers or doctors in the future. Some want to be scientists or businessmen. Still some wish to be teachers or lawers when they grow up in the days to come. Unlike other people, I prefer to be a farmer. However, it is not easy to be a farmer for Iwill be looked upon by others. Anyway,what I am trying to do is to make great contributions to agriculture. It is well known that farming is the basic of the country. Above all, farming is not only a challenge but also a good opportunity for the young. We can also make a big profit by growing vegetables and food in a scientific way. Besides we can apply what we have learned in school to farming. Thus our countryside will become more and more properous. I believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. All the working position can provide him with a good chance to become a talent. 1 ————来源网络整理，仅供供参考

个人先进事迹简介

个人先进事迹简介 01 在思想政治方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.利用课余时间和党课机会认真学习政治理论,积极向党组织靠拢. 在学习上,xxxx同学认为只有把学习成绩确实提高才能为将来的实践打下扎实的基础,成为社会有用人才.学习努力、成绩优良. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质和从容、坦诚、乐观、快乐的生活态度,乐于帮助身边的同学,受到师生的好评. 02 xxx同学认真学习政治理论,积极上进,在校期间获得原院级三好生,和校级三好生,优秀团员称号,并获得三等奖学金. 在学习上遇到不理解的地方也常常向老师请教,还勇于向老师提出质疑.在完成自己学业的同时,能主动帮助其他同学解决学习上的难题,和其他同学共同探讨,共同进步. 在社会实践方面,xxxx同学参与了中国儿童文学精品“悦”读书系,插画绘制工作,xxxx同学在班中担任宣传委员,工作积极主动,认真负责,有较强的组织能力.能够在老师、班主任的指导下独立完成学院、班级布置的各项工作. 03 xxx同学在政治思想方面积极进取,严格要求自己.在学习方面刻苦努力,不断钻研,学习成绩优异,连续两年荣获国家励志奖学金；作

为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质.

明胶的生产工艺

明胶的具体生产方法有4种：即碱法、酸法、盐碱法和酶法等。国内外普遍使用的是碱法生产。现将工艺过程叙述如下：原料整理：将不同种类的原料进行分类整理，如牛皮与猪皮；湿皮与干皮等应分开，拣出不合规格的皮另行处理。带毛皮可用5%石灰乳或0.5~1%的硫化溶液浸泡，将毛脱去。鲜猪皮的脂肪层应刮去。干皮要泡在清水中浸软。石灰水预浸:将整理好的皮原料放入1%左右的石灰水中浸渍1~2d，然后切成小块。水力除污:将皮块与水连续地加入水力除脂机内，利用水力的冲击作用和高速铁锤的机械作用，清洗除脂肪和污物。石灰水浸渍：将去脂的皮块放入浸渍池中，用2~4%的石灰水（比重1.015~1.035）浸渍。湿皮与水的比例为1: 3~4，pH值为12.0~12.5。温度最好在15℃，时间为15—90d。气温高时石灰水浓度可低些，气温低时其浓度可增大。此工序称“发皮”；是明胶生产的关键工序之一。洗涤中和：待皮块膨胀后，捞出用水充分洗涤，经过多次洗涤，最后pH 为9.0~9.5.洗涤后，用酸中和剩余的石灰，先加水使原料浸没，在不断搅拌下用水洗净，一般需8~12h内完成。熬胶浓缩：先在胶锅内放入热水，然后将原料倒入，注意不要让皮块粘结成团，同时缓慢升温至55~65℃，热浸6~8h后放出胶汁；再向锅内加入热水，使水温较前次提高5~100℃继续熬胶，依此类推，进行多次，每次温度也相应地逐步升高，最后一次可以煮沸。将所得稀胶汁在600℃左右用过了滤棉、活性炭或硅藻土等作助滤剂，以板框式压滤机过滤，得澄清胶液，胶液再用离心机分离，进一步除去油脂等杂质。再将胶液放入减压浓缩罐中，控制温度65~700℃进行蒸发浓缩，当胶液变浓时，可改为60~650℃继续减压浓缩。根据胶液质量和干燥设备条件掌握胶液浓缩的浓度，如用冷热风空调干燥时，胶液浓度比重1.050~1.080（500℃）含胶量为23~33%即可。凝胶干燥，经浓缩的胶液，乘热加入一定量的过氧化氢·亚硫酸或尼泊金，既漂白又防腐。将浓胶液在滴在冷辊上，即形成细细的胶条，在刮在容器内运到烘床上烘干。以冷热风干燥至凝胶水分为10~12℃时，再经粉碎即为成品。亦有将浓胶液滴于滚筒后，干燥即得半圆球形胶粒。

自我管理演讲稿英语翻译

尊敬的领导，老师，亲爱的同学们，大家好！我是5班的梁浩东。今天早上我坐车来学校的路上，我仔细观察了路上形形色色的人，有开着小车衣着精致的叔叔阿姨，有市场带着倦容的卖各种早点的阿姨，还有偶尔穿梭于人群中衣衫褴褛的乞丐。于是我问自己，十几年后我会成为怎样的自己，想成为社会成功人士还是碌碌无为的人呢，答案肯定是前者。那么十几年后我怎样才能如愿以偿呢，成为一个受人尊重，有价值的人呢？正如我今天演讲的题目是：自主管理。大家都知道爱玩是我们孩子的天性，学习也是我们的责任和义务。要怎样处理好这些矛盾，提高自主管理呢？首先，我们要有小主人翁思想，自己做自己的主人，要认识到我们学习，生活这一切都是我们自己走自己的人生路，并不是为了报答父母，更不是为了敷衍老师。我认为自主管理又可以理解为自我管理，在学习和生活中无处不在，比如通过老师，小组长来管理约束行为和同学们对自身行为的管理都属于自我管理。比如我们到一个旅游景点，看到一块大石头，有的同学特别兴奋，会想在上面刻上：某某某到此一游话。这时你就需要自我管理，你需要提醒自己，这样做会破坏景点，而且是一种素质低下的表现。你设想一下，如果别人家小孩去你家墙上乱涂乱画，你是何种感受。同样我们把自主管理放到学习上，在我们想偷懒，想逃避，想放弃的时候，我们可以通过自主管理来避免这些，通过他人或者自己的力量来完成。例如我会制定作息时间计划表，里面包括学习，运动，玩耍等内容的完成时间。那些学校学习尖子，他们学习好是智商高于我们吗，其实不然，在我所了解的哪些优秀的学霸传授经验里，就提到要能够自我管理，规范好学习时间的分分秒秒，只有辛勤的付出，才能取得优异成绩。在现实生活中，无数成功人士告诉我们自主管理的重要性。十几年后我想成为一位优秀的，为国家多做贡献的人。亲爱的同学们，你们们？让我们从现在开始重视和执行自主管理，十几年后成为那个你想成为的人。谢谢大家！

关于工作的英语演讲稿

关于工作的英语演讲稿【篇一：关于工作的英语演讲稿】关于工作的英语演讲稿 different people have various ambitions. some want to be engineers or doctors in the future. some want to be scientists or businessmen. still some wish to be teachers or lawers when they grow up in the days to come. unlike other people, i prefer to be a farmer. however, it is not easy to be a farmer for iwill be looked upon by others. anyway,what i am trying to do is to make great contributions to agriculture. it is well known that farming is the basic of the country. above all, farming is not only a challenge but also a good opportunity for the young. we can also make a big profit by growing vegetables and food in a scientific way. besides we can apply what we have learned in school to farming. thus our countryside will become more and more properous. i believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. all the working position can provide him with a good chance to become a talent. 【篇二：关于责任感的英语演讲稿】 im grateful that ive been given this opportunity to stand here as a spokesman. facing all of you on the stage, i have the exciting feeling of participating in this speech competition. the topic today is what we cannot afford to lose. if you ask me this question, i must tell you that i think the answer is a word---- responsibility. in my elementary years, there was a little girl in the class who worked very hard, however she could never do satisfactorily in her lessons. the teacher asked me to help her, and it was obvious that she expected a lot from me. but as a young boy, i was so restless and thoughtless, i always tried to get more time to play and enjoy myself. so she was always slighted over by me. one day before the final exam, she came up to me and said, could you please explain this to me? i can not understand it. i

明胶提纯工艺

明胶提纯工艺北京希涛技术开发有限公司、

明胶小试验使用说明书一、明胶-1号、明胶-2号的配制方法 1.明胶-1号配制浓度：10‰ 2.明胶-2号配制浓度：10‰ 3.具体溶解方法：先取100ml水放在烧杯中，用搅拌器搅动使水旋转起来，将1g明胶-1号、明胶-2号干粉分别缓慢均匀加入水中，注意防止加在杯壁上，搅拌10-20分钟，使其完全溶解。二、实际操作 1.取待处理明胶液100ml，先加入0.5g活性白土搅拌均匀。 2.再加入10‰浓度的明胶-1号溶液2-3ml，搅拌2-3分钟后，观察明胶液内形成的絮团是否均匀悬浮，如否，搅拌至使其均匀悬浮； 3.最后加入10‰浓度的明胶-2号溶液1-2ml，先以较快的搅拌速度使其混合均匀，然后缓慢搅拌，搅拌1-2分钟，慢慢就能看到清澈的上清液。三、最终现象被提纯的明胶液上清液呈淡黄色透明油状液体，在底部形成少量较大柔软的絮团。透明度能达200mm；其它各种杂质含量比处理前降低许多，使明胶的质量大幅度提高。四、实验室投加量生产车间投加量换算公式 a×1% = c (g/t) b×1‰×1‰ 式中代号： a：小试投加量单位：ml b：胶水量单位：ml c：生产投加量单位：g/t

明胶提纯工艺当中流程及使用一、配药 1.明胶-1号、明胶-2号均配成10‰浓度的水溶液。 2.小包装打开后应尽早配成水溶液，干粉易吸潮将给配制带来不便。 3.配药时应将药粉均匀分散抖在进水瀑布上，并同时搅拌溶液防止起团。 4.干粉放完后应继续搅拌20分钟以上，使其充分溶解。 5.水溶液理论上保持七天，尽量三天用完二、操作要求：明胶温度60°C，均匀充分搅拌起来 1．先加入活性白土，投加量为公斤/吨胶水 2．搅拌3-5分钟加入1号 3．观察所起絮团大小、稠稀、均匀等 4．当絮团均匀、很稀、悬浮、无丝时加入2号 5．颜色变浅黄色并迅速下沉，悬浮物较少，无丝即可三、明胶提纯的现象及处理方法

关于时间管理的英语演讲

Dear teacher and colleagues: my topic is on “spare time”. It is a huge blessing that we can work 996. Jack Ma said at an Ali's internal communication activity, That means we should work at 9am to 9pm, 6 days a week .I question the entire premise of this piece. but I'm always interested in hearing what successful and especially rich people come up with time .So I finally found out Jack Ma also had said :”i f you don’t put out more time and energy than others ,how can you achieve the success you want? If you do not do 996 when you are young ,when will you ?”I quite agree with the idea that young people should fight for success .But there are a lot of survival activities to do in a day ,I want to focus on how much time they take from us and what can we do with the rest of the time. As all we known ,There are 168 hours in a week .We sleep roughly seven-and-a-half and eight hours a day .so around 56 hours a week . maybe it is slightly different for someone . We do our personal things like eating and bathing and maybe looking after kids -about three hours a day .so around 21 hours a week .And if you are working a full time job ,so 40 hours a week , Oh! Maybe it is impossible for us at