Polyhydroxyalkanoate production during wastewater treatment

Abstract

A wastewater treatment process elicits microorganisms to convert a waste stream/organic resource to intracellular biopolymer polyhydroxyalkanoate (PHA). The process includes (i) waste stream/organic resource composition feed criteria, (ii) configuration coupled with operational parameters, and (iii) PHA-laden biomass separation and stabilization. A waste stream/organic resource capable of producing enhanced levels of PHA may be selected based on a combination of criteria, which may include short chain fatty acid concentration, protein concentration, polysaccharides concentration, and total suspended solids concentration. The waste stream is introduced into an aeration basin upon a specific configuration and operated under various parameter combinations for selecting/enriching microorganisms capable of producing PHA. The PHA-laden biomass is separated and stabilized for downstream PHA related product beneficial uses. The present process achieves concurrent wastewater treatment and PHA production, where PHA level (of more than 10% on a cell-weight basis) otherwise could not be obtained.

What is claimed is: 
     
         1 . A process for polyhydroxyalkanoate (PHA) production during wastewater treatment, the process comprising:
 providing a waste stream suitable for increased PHA production;   introducing the waste stream into an aeration basin at a location along the length of the aeration basin;   introducing a return activated sludge (RAS) into the aeration basin at a location substantially near the beginning of the aeration basin;   operating the aeration basin under operational parameters that provide a famine-feast regime that promotes the production of PHA by microorganisms in the aeration basin;   processing a treated waste stream from the aeration basin to separate activated sludge (AS) from an effluent, wherein a first portion of the AS is returned to the aeration basin as the RAS; and   processing a second portion of the AS to produce a stabilized PHA-laden biomass.   
     
     
         2 . The process of  claim 1 , wherein providing the waste stream comprises:
 evaluating characteristics of the waste stream; and   determining that the waste stream is suitable for increased PHA production based on the characteristics of the waste stream.   
     
     
         3 . The process of  claim 2 , where the characteristics of the waste stream evaluated comprise a short chain fatty acids concentration, a polysaccharides concentration, a protein concentration, and a total suspended solids concentration. 
     
     
         4 . The process of  claim 1 , wherein providing the waste stream comprises pre-treating an initial waste stream to produce the waste stream suitable for increased PHA production. 
     
     
         5 . The process of  claim 4 , wherein pre-treating the initial waste stream comprises processing the initial waste stream using solids fermentation. 
     
     
         6 . The process of  claim 4 , wherein pre-treating the initial waste stream comprises reducing total suspended solids. 
     
     
         7 . The process of  claim 1 , wherein the location at which the waste stream is introduced into the aeration basin that range from approximately ¼ to ¾ along the length of the aeration basin. 
     
     
         8 . The process of  claim 1 , wherein the waste stream has short chain fatty acids more than 1 mM. 
     
     
         9 . The process of  claim 1 , wherein the waste stream has polysaccharides less than 6 mM. 
     
     
         10 . The process of  claim 1 , wherein the waste stream has protein less than 1 mM. 
     
     
         11 . The process of  claim 1 , wherein the waste stream has total suspended solids concentration less than 200 mg/L. 
     
     
         12 . The process of  claim 1 , wherein the aeration basin is operated as a plug-flow reactor. 
     
     
         13 . The process of  claim 1 , wherein the operational parameters for the aeration basin include an influent COD loading rate between 800 mg/L/day and 3,500 mg/L/day. 
     
     
         14 . The process of  claim 1 , wherein the operational parameters for the aeration basin include a hydraulic retention time more than 1.5 days. 
     
     
         15 . The process of  claim 1 , wherein the operational parameters for the aeration basin include a food-to-microorganism ratio between 0.8 and 3. 
     
     
         16 . The process of  claim 1 , wherein processing the second portion of the AS to produce the stabilized PHA-laden biomass comprises processing the second portion of the AS using dewatering, microbial inactivation, and drying. 
     
     
         17 . A process for polyhydroxyalkanoate (PHA) production during wastewater treatment, the process comprising:
 providing a waste stream suitable for increased PHA production;   introducing the waste stream and a return activated sludge (RAS) into an aeration basin;   operating the aeration basin under operational parameters that provide a feast regime as a conventional activated sludge (AS) process; processing a treated waste stream from the aeration basin to separate AS from an effluent;   introducing a first portion of the AS into a return stream reactor, wherein an effluent AS from the return stream reactor is returned to the aeration basin as the RAS;   operating the return stream reactor under operational parameters that provide a famine regime to select microorganisms capable of producing PHA; and   processing a second portion of the AS to produce a stabilized PHA-laden biomass.   
     
     
         18 . A process for polyhydroxyalkanoate (PHA) production during wastewater treatment, the process comprising:
 identifying a biodegradable, high-carbon content waste stream having PHA precursor metabolites, the waste stream having a short chain fatty acids more than 1 mM, polysaccharides less than 6 mM, protein less than 1 mM, and total suspended solids concentration less than 200 mg/L;   introducing the waste stream into an aeration basin at a location approximately ¼ to ¾ along the length of the aeration basin;   introducing a return activated sludge (RAS) into the aeration basin at a location substantially near the beginning of the aeration basin;   operating the aeration basin as a plug-flow reactor with the following operational parameters: an influent COD loading rate between 800 mg/L/day and 3,500 mg/L/day, a hydraulic retention time more than 1.5 days, and a food-to-microorganism ratio between 0.8 and 3;   transferring a treated waste stream from the aeration basin to a clarifier that separates activated sludge (AS) from an effluent, wherein a first portion of the AS is returned to the aeration basin as the RAS; and   separating and stabilizing PHA-laden biomass from a second portion of the AS.