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3.2.2. CMF-S installation The mean SDI15-value was 2.8 with a minimum of 1.4 and a maximum of 4.3. However in the last weeks of the tests the SDI's improved and were comparable to those of the CMF and ZeeWeed fĂ­ltrate.

The organic load of the effluent was partially removed; no bacteria were found in the filtrate (table 3). The log removal for HPC was around 2 but it the counts increased with time. This could be due to the location of the installation. Unlike the CMF, both the CMF-S and the ZeeWeed installations were installed in open air near the aeration basin of the sewage plant. Small sewage droplets in the atmosphere could have contaminated the air (compressor) and the filtrate reservoir. A sample taken while chloraminating the feed resulted in lower counts that proved the effectiveness of this method.

3.2.3. ZeeWeed installation In the first part of the tests the mean SDIis-value was 3.3 but after replacement of the module it decreased to 2.6 with a minimum of 1.6 and a maximum of 3.5.

The organic load of the effluent was partially removed and no bacteria were found in the filtrate (table 2). The mean log removal for HPC was around 3 but here also a small increase of counts was observed although not in the same extent as on the CMF-S. The pH of the filtrate produced with the ZeeWeed unit was slightly higher (table 2) presumably by stripping of carbon dioxide during the back pulse4 (airflow).

3.2.4. Particle counting On September 8th a Met One 215W particle counter was installed on both submerged systems. It continuously counted particles greater than lpm. Due to the backwash it was difficult to get stable counts, especially on the CMF-S system where the backwash cycle lasted longer.

On the ZeeWeed filtrate, the amount of particles never exceeded 20 counts/ml and most of the results were between 5 and 10 counts/ml; on the CMF-S filtrate it was slightly higher with a majority of counts between 0 and 20 counts/ml.

Table 3. Quality of the wastewater effluent of the WWTP at Wulpen compared to the filtrate quality of CMF-S_

Parameter

Effluent

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