1、Process Biochemistry 50(2015262271Contents lists available at ScienceDirect ProcessBiochemistryj o u r n a l h o m e p a g e :w w w. e l s e v i e r. c o m /l o c a t e /p r o c b ioReviewA review on anaerobic biolm reactors for the treatment of dairy industry wastewater Dogan Karadag , Oguz Emre K&

2、#246;rog lu, Bestami Ozkaya, Mehmet CakmakciYildiz Technical University, Department of Environmental Engineering, Davutpasa, Istanbul, Turkeya r t i c l ei n f oArticle history:Received 25September 2014Received in revised form 7November 2014Accepted 15November 2014Available online 22November 2014Key

3、words:Dairy wastewater Anaerobic treatment Biolm reactor Methane yielda b s t r a c tThe dairy industry produces signicant quantities of wastewater that have a high potential to pollute the environment if it is not properly treated. Dairy wastewater is rich in organic materials along with other poll

4、utants, and anaerobic treatment technologies have been successfully applied due to its high biodegradability. Several research papers have been published on the application of anaerobic biolm technologies for dairy wastewater under different operational conditions. This paper provides a critical rev

5、iew focusing on biolm reactors for anaerobic treatment of dairy wastewaters of varying strengths. The effects of organic loading rate and hydraulic retention time on the performance of bioreactors are discussed and operational problems are summarized. Evaluation of reports indicates that biolm reac-

6、tors have great performance stability and hybrid bioreactors provide higher organic matter removal and methane production. Among bioreactors, up-ow anaerobic lter packed with varying media has pro-vided higher treatment efciency and it has higher tolerance against hydraulic shock loadings and heavy

7、metal toxicity. Furthermore, more research should be conducted on low-temperature applications to increase net energy gain from dairy wastewaters.©2014Elsevier Ltd. All rights reserved.Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2632. Dairy wastewater characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2633. Anaerobic treatment of dairy wastewaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2634.Anaerobic biolm reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2644.1. Biolm support materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12、 . . . . . . . . . . . . . . . . . . . . . . . . . 2644.2. Anaerobic lter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13、. . . . . . . . . . . . . 2644.3. Anaerobic uidized bed reactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2664.4. Anaerobic

14、moving biolm reactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2674.5. Anaerobic sequencing biolm batch reactor . . . . . . . . .

15、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2684.6. Hybrid anaerobic biolm reactors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2684.7. Evaluation of anaerobic biolm reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2695.Conclusions and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18、. . . . . . . . . . . . . . . . . . . 270Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19、 . . . . . . . . 270References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20、 . . . .270Abbreviations:AF, anaerobic lter; AFBR, anaerobic uidized bed reactor; AMBBR, anaerobic moving biolm reactor; ASBBR, anaerobic sequencing biolm batch reactor; ASBR, anaerobic sequencing batch reactor; BFBR, Buoyant lter bioreactor; BOD 5, 5-day biochemical oxygen demand; COD, chemical oxy

21、gen demand; CSTR, continuously stirred tank reactor; DUHR, downowupow hybrid bioreactor; FOG, fat, oil and grease; GAC, granular activated carbon; HRT, hydraulic retention time; LCFA, long chain fatty acids; OLR, organic loading rate; UASB, upow anaerobic sludge blanket bioreactor; VFA, volatile fat

22、ty acids; VLR, volumetric organic loading. Corresponding author. Tel.:+905554889764.E-mail address:dogankaradag(D.Karadag.D. Karadag et al. /Process Biochemistry 50(20152622712631. IntroductionThe dairy industry has a worldwide importance since it is an essential contributor to human nutrition and h

23、as a high economic value. In the dairy industry, raw milk is transformed to milk, yogurt, cheese, butter, ice cream, milk powder and various types of desserts by various manufacturing processes. Wastewater is generated by washing of milking equipment and milk containers, quality control laboratory a

24、nalyses, and from by-products of whey, cheese, and ice-cream making processes. Major constituents of dairy wastewa-ter are lactose, soluble proteins, lipids, mineral salts and detergents while low concentrations of some heavy metals have been reported in wastewater from control laboratories 13. Dair

25、y wastewater is generally characterized by its relatively elevated temperature (3040 C and high strength with its COD concentration up to 80g L 146.In order to remove suspended, colloidal and dissolved con-stituents from dairy wastewater, physico-chemical treatment tech-nologies including electroche

26、mical 7,8, coagulationocculation 9,10, adsorption 11and membrane treatment 12,13have been applied. Aerobic technologies have limited application for the treat-ment of organics in dairy wastewater due to the high organic load, extensive energy requirements for oxygen supply, oxygen transfer limitatio

27、ns, large quantity of sludge production and difculties in solids settling and thickening 14. Anaerobic treatment has been successfully applied for the treatment of heavily polluted wastewa-ters and has the advantages of lower nutrient requirement and less sludge production 15. During anaerobic degra

28、dation of organic matter, energy-rich methane gas is produced which is an economi-cally viable energy source if it is combusted in a combined heat and power plant 16,17. The high COD concentration and temperature of dairy wastewater gives it a signicant potential for anaero-bic treatment 18. Several

29、 bioreactor types have been applied for the anaerobic treatment of dairy wastewaters. Since dairy indus-try wastewater is high volume and heavily polluted, granule and biolm based reactors are suitable because of the capability for high-rate removal of organics along with energy recovery. In the pre

30、sent work, publications on biolm reactors have been reviewed for operational strategies and performance on the basis of organic removal and methane production from dairy industry wastewaters.2. Dairy wastewater characteristicsDairy industry generates huge amount of wastewaters, approximately 0.210L

31、of waste per liter of processed milk 19. Wastewater generation and characteristics are signicantly affected by several parameters such as scale of the factory, type of processing, the efciency and simplicity of methods used for cleaning of equipment, operating practices, methods used forTable 1Dairy

32、 industry wastewater characteristics.Wastewater sourcepHCOD (gL 1BOD 5(gL 1Solids (gL 1Volatile solid (gL 1Nitrogen (mgL 1Phosphorus (mgL 1FOG (gL 1Reference Whey 4.46604059(TS1.5NA6.964.94NA 1.1(TSS0.99NANANA 24Milk permeate5.556.5255.2063.48NA2.673.80(TSSNA300400(TN350450NA25Milk processing4.07.05

33、103537(TSNA20150(TKN5070NA89(TKN9.9NA27Dairy811261.240.351(TSS0.330.945060(TKN20500.30.528Dairy7.152.83.88(TS1.3516.5(TKN38.6NA29NA:not available; TS:total solid, TSS:total suspended solid; TN:total nitrogen; TKN:total Kjeldahl nitrogen; FOG:fats, oil and grease.efuent disposal, type of water source

34、s and the cost of water 20. Some reported characteristics values of dairy wastewaters are given in Table 1. Dairy wastewater is generally in neutral condi-tions whereas pH of ice-cream wastewater is slightly acidic and it decreases until to 4.46in whey wastewater. Organic content of dairy wastewater

35、 as in the terms of COD and BOD 5changes in wide range according to type of processing. COD concentra-tion in dairy industry is between 2and 6g L 1while it increases up to 10g L 1in milk-processing efuent and the highest val-ues have been reported for whey wastewater up to 70g L 1. Dairy wastewater

36、is also characterized by high concentration of solids with half of its as in volatile form. The highest reported amount of total solid was 59g L 1in whey while very little amount was in volatile form. Nitrogen and phosphorus contents of dairy wastewater are considerably different in each processing

37、efu-ent while those were comparatively lower than other industrial sources.3. Anaerobic treatment of dairy wastewatersBiochemical processes in anaerobic bioreactors are accom-plished by mixed cultures of acidogenic and methanogenic bacteria while each microbial group has different optimal environmen

38、tal conditions and kinetics. Anaerobic treatment systems can be clas-sied as granule and biolm reactors according to the distribution of the microorganisms. Both bioreactor types can be successfully operated under high organic loading rates (OLRswith effective treatment efciency and energy recovery

39、from heavily polluted wastewaters. Establishing the best conditions for the whole micro-bial community is difcult; therefore, development of optimal conditions for methanogenic bacteria supplies successful opera-tion of anaerobic degradation 30. Several factors including pH, temperature, organic loa

40、ding rate, presence of inhibitory matters and reactor conguration may affect the performance of anaer-obic systems. Researchers have applied various biolm reactors for the treatment of dairy wastewaters and optimized operational parameters until the bioreactors were able to achieve steady-state cond

41、itions. There is, however, no uniform agreement on the deni-tion and required duration of steady-state conditions, and various strategies have been applied. Generally, steady state conditions have been determined by monitoring the standard deviations in the values of methane generation and organic r

42、emoval efciency. Borja and Banks 23accepted steady-state conditions when the variation in monitored parameters was less than 1%,while most researchers extended the variations to 5%and 10%25,31. On the other hand, some researchers have dened the steady-state condi-tions according to multiples of the

43、hydraulic retention time (HRTduration. Kundu et al. 32applied steady-stage duration as two HRT while some researchers preferred at least 5HRT 2,33or 717264D. Karadag et al. /Process Biochemistry 50(2015262271HRT 34. Furthermore, Kisielewska et al. 35dened the steady-state as within 5%standard variat

44、ion and 1719times of the HRT. Anaerobic treatment process is strongly dependent on oper-ational pH of the bioreactor. Researchers have reported that no methane was produced from dairy wastewater at pH values below 4.5while methane producing is favorable between pH 6.5and 7.536,37. During the anaerob

45、ic degradation of organic content of dairy wastewater, volatile fatty acids could rapidly accumulate within bioreactor and decrease the pH. Additionally, lack of suf-cient buffering capacity could lead to failure in bioreactor operation and low pH may inhibit methanogenic activity. The optimum pH ra

46、nge could be maintained by inserting on-line pH controller into the bioreactor 38or by addition of buffering chemicals into the feed 39,40. Anderson and Yang 41investigated the buffering effects of different chemicals, and found that Na 2CO 3and NaHCO 3 had superior buffering capacity than NaOH at a

47、round pH 7.0. During the treatment of dairy wastewater, researchers have used mainly NaHCO 326,42,43and NaOH 2429to adjust pH at desired levels. Moreover, mixing of dairy wastewater with alkaline-rich waste-water could be another solution to provide adequate buffering capacity within the bioreactor.

48、The inorganic contamination of dairy efuents, especially whey wastewater, is associated with addition of NaCl, KCl and calcium salts during the production processes 14. Sodium toxicity is a common problem which inhibits the methane-producing consortia during the anaerobic treatment of highly concent

49、rated food wastes 44. Dairy industry efuents are also rich in lipids and high lipid content could negatively affect the anaerobic bioreactor perfor-mance 19. Lipids are slowly degraded and cause some operational problems such as biomass otation, microbial wash-out and limited substrate transfer with

50、in the biolms 22.4. Anaerobic biolm reactorsAnaerobic biolm reactors are attractive with their high load-ing capacities, concentrated biomass, resistance to hydraulic or organic overloads, and no requirement of mechanical mixing 2843,14,44,45. Compared to conventional anaerobic treatment systems, bi

51、olm reactors could signicantly reduce start-up time and increase organic loading rates up to vefold 46. Biolms are microbial communities attached to support materials and they have ability for effective removal of organics and methane production 4749. Various types of biolm reactors have been succes

52、sfully applied for the treatment of high-strength efuents from food industry and dairy production 50,51.4.1. Biolm support materialsIn anaerobic biolm reactors, microorganisms are immobilized on support materials and organic matter removal efciency is related with the nature and properties of materi

53、als 52. Dairy wastewater treatment in anaerobic lter (AFhas been conducted by using various support materials such as seashell 53, char-coal, plastic materials 28,54, ceramic 55, sintered glass 56, re bricks 52, natural stones including limestone, gravel 52, pumice 43, clay 46and rocky aggregates 57

54、,58. Patel et al. 45 compared the whey treatment performances of different support materials in an up-ow AF at 37 C. They reported that charcoal-packaged AF provided the highest COD removal, CH 4content and biogas production with the lowest amount of total VFA, con-troversially; pumice had the lowes

55、t treatment efcient. Authors associated the lower treatment performance with the low surface area of pumice.Researchers have studied the dairy wastewater treatment in an AF by using different clay minerals as support media 46,59. Experimental results indicated that surface area of clay was effec-tiv

56、e on the biodegradation kinetics and COD removal efciency was high as up to 95%.CH 4production was found related with surface morphology, capacity of microorganism adsorption and exchange of micronutrients from clays. Porosity of support mate-rials is also very important on reactor performance and i

57、t was reported that porous media provided better performance at higher OLR 54. The reactor with non-porous media showed instability above an OLR of 4kg COD m 3d 1whereas the reactor with the porous material was still stable at OLRs of up to 21kg COD m 3d 1 54,56. Concentrated biomass was developed i

58、n the porous media, whereas most of unattached biomass was retained in the voids of the non-porous media. Recently, researchers have proven that magneto-active material is effective on the hydrolysis and acido-genesis of dairy wastewater in AF 60. Magneto-active packing media was prepared by coating plastic material with iron and cop-per powders. The study was conducted at 35 C and experimental results indicated that magneto-active media sig