This graduation thesis for the master Strategic Product Design at the Delft University of Technology is written as a research and advice report for the civil engineering and advice agency Witteveen+Bos. More specifically for the Digital Acceleration product-market combination (PMC). The report answers the following question: “Is Witteveen+Bos as an organization structurally fit for developing, maintaining and marketing digital products?”...

Biofouling and scaling are ongoing challenges for reverse osmosis (RO) membranes application in wastewater reclamation. Adequate RO feed pretreatment is necessary for biofouling and scaling control. The objective of this thesis was evaluated the effectiveness of ion exchange treatment with weak acid cation (WAC) and strong base anion (SBA) resins columns, in series, after ultrafiltration (UF) treatment for the pretreatment of municipal wastewater treatment plant effluent in order to be used for RO desalination. Specifically, the performance of two SBA resins, the Amberlite SCAV4 Cl (SCAV4) and the Amberlite IRA458 Cl (IRA458) was assessed at three regeneration levels (120, 100 and 80 g NaCl/Lr). The effect of the different regeneration levels on anions removal (sulfate, phosphate and nitrate), total organic carbon (TOC) removal and the operational exchange capacity was researched. Moreover, the subsequent effect on RO biofouling and scaling potential was investigated based on the product water quality of the two SBA resins with bio-growth potential tests and software tests (WAVE design, PHREEQC 3 and Avista Ci), respectively. Phosphate and sulfate removal was above 97% for both resins at all regeneration levels. TOC removal of about 70% was achieved in all cases. It was also observed that sulfate, phosphate and TOC removal remained the same up to the point where product nitrate concentration reached its feed concentration. The removal of nitrate was influenced by the regeneration level. For both SBA resins, a lower regeneration level caused a higher nitrate baseline leakage in product water, hence to a lower removal. The macroporous SCAV4 found to have higher selectivity towards nitrate compared to the gel IRA458. Nevertheless, the anion selectivity order for both SCAV4 and IRA458 was HCO3- < NO3- < HPO42- < SO42-. A minor increase in the operational exchange capacity for both SBA resins was observed at higher regeneration levels. Overall, the influence of the different regeneration levels was found to be limited towards the product water quality and the operational exchange capacity. Also, both SBA resins resulted to similar product water quality. The operational exchange capacity of IRA458 at each regeneration level was higher than that of SCAV4, due to the former’s greater total exchange capacity. The RO feed water quality produced without ion exchange pretreatment (only UF) supported bacterial growth up to 54 ± 1.5 × 106 cells/mL. The RO feed water qualities produced with ion exchange pretreatment in the cases of SCAV4 and IRA458 supported bacterial growth up to 3.4 ± 0.3 × 106 cells/mL and to 1.25 ± 0.2 × 106 cells/mL, respectively. The resulted reduction in the bacterial growth potential was above 90% after ion exchange treatment with either one of the tested SBA resins. The growth-limiting nutrient for the RO feed water qualities produced by either SBA resin was phosphorus. The bacterial growth supported by the two RO feed water qualities produced with ion exchange pretreatment after extra phosphorus addition was 80% lower than that supported by the RO feed water quality produced without ion exchange. This difference suggests that both SBA resins removed a considerable fraction of assimilable organic carbon (AOC). It was concluded that ion exchange pretreatment with either one of the tested SBA resins resulted in nutrients removal (P and C) in the RO feed that lowers the biofouling potential compared to RO feed pretreatment with only UF. The software results suggest lower scaling potential for several scalant types in the RO feed after ion exchange treatment with either one of the tested SBA resins. Among them was calcium phosphate, which was found to have high scaling potential in RO feed without ion exchange treatment (only UF) either with or without anti-scalant dosing. However, the scaling potential of some silica and iron based minerals was high, thus anti-scalant dosing might be required.

Galdieria sulphuraria (G. sulphuraria ) is a eukaryotic, extremophilic, spherical and unicellular species of red algae. G. sulphuraria can grow at very low pH-values (pH 0.05 – 5.0) and high temperatures (35 – 56 °C). The growth conditions of G. sulphuraria make it suitable for axenic cultivation because the low pH and high temperature minimalize the risk of microbial contamination. Next to its ability to remove nutrients in wastewater treatment, G. sulphuraria is a prospective producer of a valuable product, Phycocyanin (PC), a thermostable blue pigment-protein complex, which is used as, among others food additive and food colorant.

These characteristics of G. sulphuraria lead its selection by Evides Industriewater for the uptake of the ammonium present in the reverse osmosis (RO) concentrate of New Energy and REsources from Urban Sanitation (NEREUS). NEREUS focuses on the re-use of nutrients present in wastewater, among others ammonium. One of the goals of NEREUS is to re-use the ammonium present in the RO concentrate with the use of algae. In order to recover ammonium from the RO concentrate of NEREUS, it is necessary to test whether G. sulphuraria is capable of growing on such medium. The possibility of cultivating of G. sulphuraria on the RO concentrate from water and resource recovery pilot plant of NEREUS was investigated in this thesis.

The objectives of this thesis were to find the optimal growing conditions and assess the biomass growth and nutrients consumption. Screening experiments with synthetic Allen medium, which is usually used for the cultivation of the G. sulphuraria, were conducted to obtain the best growing conditions of G. sulphuraria. In order to understand the best growing conditions for the cultivation of G. sulphuraria, the effects of several factors were investigated, which are: 1) different metabolism, 2) different nitrogen sources and concentrations (ammonium: 100 – 1000 mgNH4+-N/L and nitrate: 247 mgNO3--N/L), 3) different carbon sources (glucose, bicarbonate and CO2) and different glucose concentrations (C:N = 5:1 and 10:1), 4) different phosphate concentrations (N:P = 37:1 and 7.2:1), 5) culture densities. Ammonium with mixotrophic metabolism turned out to be the best nitrogen source. Biomass concentration on ammonium was four times higher than on nitrate. Increasing the ammonium concentration from 200 mgNH4+-N/L to 1000 mgNH4+-N/L resulted in around 25% more biomass and no firm conclusions could be drawn from the experiment performed with different phosphate concentrations. No significant increase in the growth of G. sulphuraria was observed between Carbon:Nitrogen (C:N) ratio = 5:1 and 10:1. Furthermore, culture densities higher than 0.7 g/L of biomass resulted to a slower growth of G. sulphuraria.

Experiment with synthetic RO concentrate shows that there was light limitation involved during the cultivation. Highest and fastest growth (µmax = 0.78 day-1) was observed in the mix of 40% real RO concentrate and 60% synthetic RO concentrate medium culture. Growth inhibition was observed in cultures containing RO concentrate of NEREUS. Still, G. sulphuraria did grow on RO concentrate of NEREUS. This work is contributing to the scientific and engineering community in the field of microalgae.