Analysis on the Performance of Vermifilter at Low Temperature in Winter

The performance of the vermifilter in winter was investigated. The experimental results indicated that the temperature of vermifilter bed in winter was 1~5°C higher than that of the ambient. However, the temperature was still a key factor for the vermifilter, low temperature could influence the activity of the earthworms. The filter bed temperature was positively correlated with the earthworm density. So was the unit-area biomass. Reversely, the filter bed temperature was negatively correlated with the density of the mature earthworms. The results also showed that the earthworms´ relative ingestion and digestion abilities were only about 1/3 of those in summer under the same hydraulic loading. Moreover, the removal rates of the pollutants except BOD5 of the vermifilter effluent in winter was only half of that in summer under the same hydraulic loading. The average removal rates of TN and TP were both less than 10 %. Warmer area and better heat preservation medium are recommended to be provided for the vermifilter for its excellent operation performance.