I'd probably go with something like this.

... the treatment capacity of which should be approximately 50% of the capacity of the cleaning fluid filter and degreaser.

The purification system should have a capacity/maximum flow rate of about 50% of the capacity of the wash water filter and the oil extractor.

处理能力按清洗液过滤及除油装置能力的约50%来配备

This sentence answers the question, "How big a purifier should I get?" It says the purifier works in sequence with a filter and oil extractor, and the purifier should be big enough to handle about half of the nominal capacity (max flow rate) of the filter and the oil extractor.