Bad Odour Harvested Rainwater

One problem I am facing right now is that the harvested rainwater has a bad odour. Hence, the system (used for toilet flushing only) has been temporarily suspended. On water testing, it is observed that apart from odour the water has above limit colour and turbidity. I am planning to erect a filter cum dozing unit on the delivery pumping mains. Can someone suggest the type of filter cum dozing unit for a flow of 10 m3/day?