Patent Application: US-201213423010-A

Abstract:
tricyglycerols that may be converted to biofuel are recovered from oleaginous organisms in the natural and induced foam of wastewater treatment process plants . growing oleaginous organisms in the form of comparatively dry foam simplifies harvest and is more efficient and efficacious than skimming the biomass off the top of the liquids that rely on less efficient centrifugation or filtration methods typically required to concentrate cells grown in liquids .

Description:
this invention , in broad aspect , is a process for recovering biofuel grade microbial oils from normal foaming in wastewater treatment plants by harvesting and extracting oleaginous ( oil producing ) bacteria that are cultured in the form of a thick microbial foam . the process comprises harvesting nocardioform bacteria - containing foam from wastewater treatment plants , recovering triacylglycerols ( tag ) there - from and , optionally , processing the recovered tag to biofuel — particularly bio - diesel . this system takes advantage of the tendency for filamentous nocardioform bacteria to grow directly in aeration basin waters where , despite competition from other organisms , they are still able to collect as thick hydrophobic bulk foam that floats on the surface of the aeration basin waters . this bulk foam format facilitates harvesting and concentrating the cells , as well as reducing the amount 1 of excess water that must be removed prior to oil extraction . this provides a means of economical cell harvesting , which has been a major limitation in other systems . the invention , in one embodiment , also comprises operating wastewater treatment plants to intentionally produce foam containing nocardioform bacteria for recovery of tag . filamentous , foam - causing nocardioforms responsible for most foaming at municipal wastewater treatment plants include nocardia , gordonia , dietzia and rhodooccus . this invention capitalizes upon the connection between the oil producing property of common foam - causing bacteria and the fact that the foam is an easier to harvest cell format than other microbial and algal biodiesel production systems . while there have been other disclosures of methods to extract lipids from wastewater plants and turn them into biodiesel , they do not target the tag in bacterial cells , but only the lipids that come in with the wastewater . see , for example u . s . pat . no . 7 , 638 , 314 , issued dec . 29 , 2009 . foaming ( and bulking ) is a natural phenomenon that a majority of municipal and industrial wastewater treatment plants already experience . foaming and bulking can occur as either chronic or acute microbial outbreaks , in the form of layers of thick brown foam up to a meter thick . the foam layers are composed of gas bubbles trapped and stabilized by a large mass of long , branched , hydrophobic filaments of nocardioform bacteria , including nocardia , gordonia , and rhodococcus . bacteria closely related to foam - producing nocardioform bacteria include , for example , rhodococcus opacus pd630 , which accumulates up to 78 % dry mass tag ( triacylglycerols ) as storage lipids ( table 1 ). tag lipids are the same lipid components in vegetable oils that are used for other process for biodiesel production . formation of tag lipid storage bodies occurs widely only in the group of bacteria that includes the nocardioforms ( the actinomycetes ). as a soil bacterium , r . opacus cannot be successfully cultivated in raw , unprocessed aeration basin liquids and there are currently no economical ways to produce r . opacus in the large volumes needed for biofuel production . while the level of tag in the various wastewater foams will vary , the nocardioform bacteria contained in the foam are both capable of high volume foam formation and high storage tag accumulation in raw aeration basin waters . when the limited number of bacteria capable of forming storage bodies of tag is taken into consideration , the potential correlation between foaming , during which nocardioform bacterial accumulate to a high biomass , and tag production is even more fortuitous . most bacteria do accumulate some sort of lipophilic compound in the form of an intracellular lipid - body . however , most accumulate either phb ( 3 - hydroxybutyrate ) or phas ( polyhydroxyalkanoates ). tag accumulation in storage bodies , while common among plants , is very uncommon among bacteria . the only group of bacteria capable of accumulating large quantities of tag is in fact in the nocardioforms , including nocardia , rhodococcus , gordonia , and dietzia ( table 1 ). isolates of all of these have been identified as abundant constituents of nocardioform foaming outbreaks in municipal wastewater treatment plants . tag lipid body storage content of nocardioform growing as foam on municipal wastewater has not heretofore been considered as a source of biofuel grade oil . biodiesel - grade lipids can be extracted from sludge and regular ( e . g . non - foaming ) aeration basin liquids and solids . lipid yields of almost 5 % dry weight have been obtained from activated sludge , with a production cost of $ 3 . 11 per gallon , which was higher than the $ 2 . 50 per gallon price of soy diesel at the time of publications . it was noted that increasing yields to 10 % would be required to bridge the cost gap between sludge diesel and soy diesel . the volumes dealt with at municipal wastewater facilities are not trivial . the 21 , 604 public municipal wastewater treatment facilities in the us produce over six million dry metric tons of sludge every year . foam will provide higher yield , easier to extract source of biodiesel grade lipids than sludge . conditions that promote nocardioform “ blooms ” and lead to foaming include aeration methods and influx water components . high levels of fats , oils and grease ( fog ), promote the growth of nocardioforms and wastewater treatment plants that service food manufacturers are particularly prone to foaming . proliferation of filamentous nocardioform is also promoted by conditions such as a low f / m ( food to mass ) ratio , when a plant runs with an extremely long sludge age , and when plants are run at higher temperatures . foaming is also aggravated by plant design , as plants lacking primary scum removal , or plants that recycle scum , are particularly prone to foaming . these known causes of foaming provide guidance for selection of suitable wastewater plants for tag harvesting and to means for intentionally inducing forming for biofuel production . manipulation of these conditions is used intentionally to cause treatment plants to produce foam for recovery and production of bio - diesel ( or other bio - fuels ). in one embodiment the invention will comprise selecting treatment plants that are prone to foaming and that produce relatively high tag containing nocardioform bacteria . therefore , identification of high tag bacteria is an important component of the process of the invention . to determine the suitability of any given wastewater treatment plant for foam recovery analysis of the foam is made to determine the concentration of tag producing bacteria and the variability over a period of time . the kinds of bacteria present the foam will be largely determined by the nature of the feed water content . plants with relatively constant feed content will be more suitable for the process of the invention . plants given to excessive foaming , if the foam contains sufficient tag producing bacteria , will be especially suitable as such and for conversion to intentional foaming design . such analysis can be performed by methods known in the art and can , no doubt , be improved upon for the specific purposes of this invention based on experience with various operating plants . since foaming , and the related problem of bulking , is currently viewed by the wastewater treatment industry as a problem , deliberate running of a plant in “ foaming mode ” requires detailed analysis on the implications for total plant functioning . the primary purpose of a wastewater treatment facility is to process water into a form suitable for release into the natural water system . in one embodiment of the invention other aspects of plant function are be modified achieve this balance . conventional treatment plants can be operated in a “ foam ” mode by providing conditions known to cause excess foaming . methods to promote foaming would initially be designed based on reverse engineering , using conditions known to help control foaming . there is a great deal of information on ways to reduce or control foaming . operation conditions that reduce nocardioform foaming include increasing the wasting rate in order to reduce mcrt ( mean cell residence time — a measure of sludge age ). removal of scum in return activated sludge control and increasing the f / m ( food to mass ratio ) are also known to reduce nocardioform foaming . additionally , it has been observed that high levels of fats and oils also promote nocardioform growth . taken together , these known foaming conditions teach that increasing retention time , processing cooking oils and fats , but maintaining an overall low f / m ratio would generate a condition in which nocardioform foaming is promoted . in addition to operation mode , changes to the aeration basin format might also promote foaming . it is generally accepted that having “ foam traps ”, or areas of reduced circulation , will re - seed the basin with foam - generating bacteria . also , using a return activated sludge system in which waters from the top of the basin are recycled , promotes retention and re - seeding of nocardioform . in one embodiment , separate basins or lagoons are constructed alongside the aeration basin ( the normal location of foaming ) of existing treatment plants where foaming will be intentionally promoted by providing conditions that promote foaming as described above . these basins or lagoons will , optionally , be enclosed to prevent escape of and facilitate collection of the foam . water , with foam removed can be recycled from the foaming basins into the treatment plant aeration basin or other suitable location in the process train . by “ trapping ” the foam and not letting it escape the basin , it will help to continuously “ reseed ” the waters and promote foaming . conditions to promote growth of foaming bacteria , as discussed above include high grease and oil input , longer sludge age , low organic loading rates , and septicity or low oxygen conditions needed for these filaments to overgrow the system . foam disposal into aerobic or anaerobic digesters will also result in foaming . an embodiment of the integrated process on the invention is illustrated in fig1 . foam containing tag lipids is removed from vessel 10 ( a foaming basin of a wastewater treatment plant ) to stage 12 where the foam is broken to produce a process feed stream . conduit 42 shows an optional recycle of glycerol produced in the process for use as a defoaming agent . from stage 12 the process stream passes to stage 14 for processing to break the bacteria cell wall and release tag lipids for further process in stage 16 , where the lipid stream is dewatered and otherwise prepared for the bio - diesel process . a novel means of breaking lipid foams with a sonicating device is described in us 2010 / 0261918 , pub . oct . 14 , 2010 , the appropriate teaching of which is incorporated herein by reference . glycol compounds are also effective defoaming agents . when prepared for tranesterification processing the feed stream passes to the tranesterification process stage , 18 . a product of tranesterification when using koh ( or other strong base ) catalyst , is glycerol . a recycle , 42 , stream of this produced glycerol can be used as a foam breaker in stage 12 . product biodiesel from stage 18 passes by conduit 35 to a washing stage 20 . optionally the biodiesel can be washed in stage 20 with effluent water , 40 , from the treatment plant . wash water , 36 , passes back to a forward stage of the treatment plant . washed , finished biodiesel is recovered through conduit 38 . glycerol is recovered through conduit 44 . the generic process scheme shown in fig1 is only one variation of the process of the invention showing the possibility of recycle water and recycle glycerol as a foam breaker . all elements of the process to convert lipids , except the foam collection and foam breaking stage , are known in the art — much current research on similar processes for algae processing is being conducted world - wide and improvement in every stage of the process are being made . it is contemplated that optimum developments adapted for the particular lipids of this invention will be utilized in converting wastewater foam lipids to biodiesel . a detailed description of the various processes for wastewater sludge treatment , wastewater plant operations and the processes for processing lipids and other oils to biodiesel is contained in u . s . pat . no . 7 , 638 , 314 , dec . 29 , 2009 , the relevant teachings of which are incorporated herein by reference . in the foregoing specification , the invention has been described with reference to specific embodiments thereof . it will , however , be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims . the specification is , accordingly , to be regarded in an illustrative rather than a restrictive sense . therefore , the scope of the invention should be limited only by the appended claims . 1 . alvarez , h . m ., and steinbuchel , a . 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