TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In producing PHAs in biomass, the substrate and biomass form a mixture and the substrate includes RBCOD, and the method includes generally maintaining the concentration of the RBCOD in the mixture at 1000 mg/L and below. The method comprises feeding the substrate to the biomass such that the concentration of RBCOD is generally maintained above 10 mg/L. The substrate is fed to the biomass in three or more pulses and where the frequency of the pulses is such that the respiration rate of the biomass does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent pulse fed. The method further comprises feeding the substrate to the biomass in pulses; and employing online process monitoring with UV/visible (VIS) spectroscopy, conductivity, or pH for controlling substrate feeding rate or pulse feeding frequency. The substrate and biomass are mixed together to form a substrate and biomass mixture, and the method includes controlling substrate feeding rate or pulse feeding frequency as a function of the concentration of total or dissolved organic carbon in the substrate and biomass mixture, or the concentration of COD in the substrate and biomass mixture. The method also comprises controlling substrate feeding rate or pulse feeding frequency utilizing respirometry based on dissolved oxygen concentration in the mixture, carbon dioxide concentration in the mixture, or redox potential of the mixture. Biomass is contained within mixed liquor and the method includes directing the biomass into a first zone and directing the biomass to a second zone and feeding the substrate to the biomass in the second zone, where the second zone includes a volume of mixed liquor less than the volume of mixed liquor in the first zone; and where the concentration of the substrate in the second zone is higher than the concentration of the substrate in the first zone. The method further comprises concentrating the biomass before, during, or after PHA accumulation in the biomass. Frequency of supplying the substrate to the biomass is such that the respiration rate of the biomass after at least one supply of substrate to the biomass does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent supply of substrate. Frequency of supplying the substrate to the biomass is such that the respiration rate of the biomass after each of the at least three times substrate is supplied to the biomass does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent supply of substrate. Intermittently supplying the substrate to the biomass includes: (i) intermittently pumping the substrate into a feeding zone that includes the biomass; (ii) circulating a portion of the biomass from a zone having a relatively low concentration of substrate to a zone having a relatively high concentration of substrate while the substrate is fed continuously or non-continuously; or (iii) a combination of intermittently pumping the substrate into a feeding zone that includes the biomass and intermittently bringing the biomass into contact with the substrate. The substrate and biomass form a mixture and the substrate includes BCOD and the method includes generally maintaining the concentration of the RBCOD in the mixture at 1000 mg L and below while generally maintaining the concentration of the RBCOD above 10 mg L; and where intermittently supplying the substrate to the biomass includes exposing the biomass to a series of interruptions in substrate supply such that the respiration rate of the biomass after at least one interruption does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent supply of substrate. Biomass is contained within mixed liquor and the substrate is fed intermittently to the biomass; and where the frequency of feeding the substrate to the biomass is controlled by sensing the dissolved oxygen concentration in the mixed liquor and triggering the feeding of the substrate to the biomass in response to an increase in dissolved oxygen concentration, over a selected time, that is greater than a selected threshold value. The method also comprises controlling the frequency of feeding the substrate to the biomass by correlating the dissolved oxygen concentration in the mixed liquor with a relatively low biomass respiration rate, and after the relatively low biomass respiration rate occurs, then triggering the feeding of the substrate to the biomass in response to an increase in dissolved oxygen concentration, over the selected time, that is greater than the threshold value. It further comprises treating a wastewater stream and producing a mixed cultured biomass; harvesting the mixed cultured biomass and utilizing the mixed cultured biomass to produce the PHAs; and where the method entails utilizing at least a portion of the wastewater stream or an alternative wastewater stream as the substrate fed to the mixed cultured biomass. Promoting accumulation of PHAs in biomass comprises feeding the RBCOD to the biomass in a series of pulses and controlling the frequency of the pulse feeding such that the respiration rate of the biomass after at least one pulse feeding does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent pulse of RBCOD fed. During PHA accumulation the method includes interrupting the feed of the substrate to the biomass; and controlling the frequency of interruptions such that the respiration rate of the biomass after at least one interruption does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent interruption of substrate feeding. The method further comprises biologically treating a wastewater stream with activated sludge; and where the biomass utilized for producing PHAs is taken from the activated sludge after the activated sludge has been utilized in biologically treating the wastewater stream; and where feeding the organic carbon-containing substrate to the biomass includes feeding at least a portion of the wastewater stream or an alternative wastewater stream to the biomass. In producing PHA in biomass utilizing waste activated sludge, the waste activated sludge is directed into a first zone and the wastewater influent or alternate wastewater influent which includes organic carbon-containing substrate is directed into a feeding zone; and the method includes circulating the biomass from the first zone to the feeding zone and back to the first zone and where interrupting the feed to the biomass is achieved by maintaining a relatively high substrate concentration in the feeding zone and a relatively low substrate concentration in the first zone. The first zone is a variable volume reactor and the feeding zone is a generally constant volume reactor; and where the wastewater influent or the alternate wastewater influent is mixed with the activated sludge to form mixed liquor and where the mixed liquor is circulated from the variable volume reactor to the generally constant volume reactor. The PHA accumulation process is carried out in a single reactor and where both the waste activated sludge and wastewater influent is directed into the single reactor. During PHA accumulation, the frequency of interruptions is controlled such that the respiration rate of the biomass does not drop more than 70% relative to the maximum respiration rate achieved by the biomass in response to the most recent feed supply. The method further includes biologically treating the wastewater influent with the activated sludge to remove contaminants from the wastewater influent; wasting at least some of the activated sludge utilized to treat the wastewater influent; and utilizing the biomass of the wastewater influent to produce the PHAs. In producing high molecular weight PHAs in biomass, the carbon-containing substrate is wastewater from an industrial, municipal or agricultural process, or one or more products derived to it. The amount of substrate in each supply of substrate is an amount sufficient to expose the biomass to a concentration of COD between 20 and 500 mg-COD/L. The average molecular weight of the PHAs produced is at least 400000 g/mole. Respiration rate of the biomass does not drop more than 30% relative to the maximum respiration rate achieved by the biomass in response to the most recent supply of substrate. Respiration rate of the biomass is directly or indirectly determined by online process monitoring of one or more parameters including the dissolved oxygen concentration in the mixed liquor, the kinetics of VFA removal from the mixed liquor, the oxygen consumption of the biomass, the carbon dioxide production of the biomass, and pH changes in the mixed liquor. An endpoint in PHA accumulation or saturation of PHAs is determined by turbidometnc measurements based on near-infrared back scatter methods, Raman infrared spectroscopy, build-up of RBCOD, decreased substrate uptake kinetics relative to the substrate used, decreased biomass respirometry relative to the substrate used, or its combination. The method further includes biologically treating a wastewater stream with biomass to remove contaminants; wasting at least some of the biomass; and utilizing at least some of the waste biomass as the PHA-accumulating biomass. It also comprises biologically treating a wastewater stream with activated sludge to remove contaminants from the wastewater stream; wasting at least a portion of the activated sludge; utilizing biomass contained in the waste activated sludge as the PHA accumulating biomass; and feeding the wastewater stream or an alternative wastewater stream to the PHA accumulating biomass. EXAMPLE - No suitable example given.