PhD student project: Converting wastewater treatment facilities into resource factories: Recoveri...

September 13 2017
Position Type
Full Time
Organization Type


A current societal challenge is to achieve higher value conversions from organic residuals into renewable platform materials and chemicals. To this end, waste activated sludge is rich in microbial metabolic activity and it can be a functional resource used to produce renewable resources like biopolymers. Harvested surplus biomass has been demonstrated to offer significant capacity for intracellular biopolymer accumulation. Waste municipal activated sludge can be made to accumulate approximately its organic weight in polyhydroxyalkanoates (PHAs) when fed regionally available sources of fermented organic residues. Surplus activated sludge from industrial biological wastewater treatment processes can be made to accumulate significantly higher levels of PHA. PHAs are biobased and biodegradable polymers with established commercial potential as ingredients for the bioplastics, biofuel, and chemical industries. Societal water quality management infrastructures can gain a duality in function as renewable resource (biopolymer) production facilities, if the PHAs are recovered in an efficient manner. Efficient PHA recovery methods that fit in scale and economy within regional realms of industrial and municipal water quality management activities will be an enabler to kick-start value chains in practice from the opportunity to reliably supply renewable biopolymers.


Research challenge

The crude product from a biopolymer production facility is a wet PHA-rich biomass comprising PHA and non-PHA biomass (NPB). The NPB will be dominated by microbial biomass constituents (proteins, genetic material, lipids and polysaccharides). The technology challenge is to recover, as efficiently as possible, a semi-manufactured PHA product of market value for downstream exploitation. As efficiently as possible means with:

  1. maximal exploitation of the non-PHA biomass constituents,

  2. little, but ideally, no by-products which are construed to be process wastes for treatment,

  3. streamlined integration into environmental management infrastructure and material flows,

  4. as small an economy of scale as possible to kick-start viable value chains, and

  5. a crude polymer product with relatively high thermal stability, molecular mass, and purity.


    The objective of this project will be to build on the already existing wealth of experience within the project partner team and establish fundamental insights of the polymer fate and its preservation as a foundation to generate innovation towards practical implementation of PHA recovery unit processes and methods.


This project falls under the Wetsus research theme Bioplastics. The theme stakeholders are: Paques BV (, STOWA (, and SNB (

Promotor: Mark van Loosdrecht (TU Delft)

Co-promotor: Robbert Kleerebezem, (TU Delft)

Wetsus supervisor: Dr. Alan Werker (contact for information,



Wetsus, Leeuwarden, The Netherlands

This job comes from a partnership with Science Magazine and Euraxess