Modular bioreactor platform

The modular bioreactor platform consists of different types of bioreactors that can be used in sequential and/or parallel configuration. The platform is specifically suitable for investigating sustainable solutions for environmental challenges, such as sustainable energy generation, recovery of resources from complex waste streams, and degradation of (micro)pollutants. These micropollutants are observed at trace concentration (ng/L to µg/L) in the aquatic environment (Fig 1) in the last decades. 

Figure 1. Distribution of micropollutants in the environment through various processes (http://www.eusem.org)

These compounds are a potential hazard to environmental and human health and are found in important resources, such as water used for drinking water production. The concerns of the presence of these micropollutants in the environment indicates the importance of understanding the fate and transformation of these compounds and designing technologies for their removal throughout the water cycle. Combinations of microbial, chemical and physical processes in innovative reactors are needed, and these systems need to be designed, developed and validated. Two examples of the application of hybrid systems for the treatment of micropollutant contaminated water are given below.

Case 1  Pilot-scale hybrid constructed wetlands 

Hybrid-constructed wetlands (CWs) with three CW water flow types in different combinations were installed; (1) vertical subsurface flow CW, (2) horizontal subsurface flow CW, and (3) surface flow CW. In total, six different hybrid CWs were installed, allowing to test all the possible sequences with the 3 CW types. The CWs consisted of sand and gravel, and were planted with Phragmites australis. They were fed with a synthetic medium at a flow rate of 140 L/d, resulting in an HRT of 7.5 days. Removal of phosphate, benzoic acid, and benzotriazole was studied in these systems.

Figure 2. Outdoor pilot-scale hybrid constructed wetlands at WUR-ETE

The CWs were operated for a full year, and the removal of the various compounds is summarized below. 

Figure 3. The highest removal efficiency was observed in the vertical flow CWs, and no removal was seen in the surface flow CWs. benzoic acid, nitrate, bentriazole, and TOC were removed by biodegradation, whereas phosphate and benzotriazole were removed by adsorption
Figure 4. In autumn, the plants were removed, which resulted in less input of oxygen and nutrients for microbial processes. As a consequence, lower removal of compounds that rely on microbial degradation was observed in the horizontal flow CW: benzoic acid, benzotriazole, nitrate. The vertical flow CW performs similarly as in summer
Figure 5. The surface flow CW was frozen during winter, and no operation of the hybrid-CWs was possible. When not frozen, the low temperatures and absence of plants resulted in a low microbial activity, especially in the horizontal flow CWs. The vertical flow CWs still perform better. However, the overall performance of the wetlands depended on the figuration (the used sequences) tested.

The surface flow CW was frozen during winter, and no operation of the hybrid-CWs was possible. When not frozen, the low temperatures and absence of plants resulted in a low microbial activity, especially in the horizontal flow CWs. The vertical flow CWs still perform better.

However, the overall performance of the wetlands depended on the figuration (the used sequences) tested.

Case 2  Hybrid reactor system BO3B (bio-ozone-bio) reactor

This modular system (Figure 6) combines the efficiency of biological removal and the power of ozonation to remove a broad range of micropollutants, while also providing a sustainable and cost effective technology. Wastewater treatment plant (WWTP) effluent is fed into the first reactor (bio), where DOC is removed to reduce the required ozone dose in the second reactor (ozone). In the third reactor (bio), potentially toxic ozonized transformation products are further broken down by microorganisms.

Figure 6. Schematic overview of the BO3B system

First, the removal capacity at different loading rates and ozone dosage is tested, resulting in an optimal HRT of 88 min, and an ozone dose of 0.2 g O3/g TOC (Fig 7).

Figure 7. Overview of pharmaceutical removal

In addition to the modular BO3B reactor, different modules or the first biological reactor are tested in parallel, to identify the optimal configuration. (Fig 8)

Figure 8. Picture of BR1 selection experiment BO3B system; Granular Activated Carbon, Moving Bed Biofilm or Sandfilter.

This shows the variability that can be tested in the modular reactor platform of UNLOCK.