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Tower bio-vermifilter system for rural wastewater treatment: bench-scale, pilot-scale, and engineering applications
Nie, E.; Wang, D.; Yang, M.; Luo, X.; Fang, C.; Yang, X.; Su, D.; Zhou, L. & Zheng, Z.
Abstract
This paper presents a systematic study of a
novel tower bio-vermifilter system for rural wastewater
treatment at three scales: bench-scale, pilot-scale, and
engineering applications. First, three types of bioreactors
were tested in the bench-scale experiments: earthworm
bioreactor, soil filter, and one-stage bio-vermifilter.
Experiments with the earthworm bioreactor and soil filter
determined the optimum earthworm density and soil layer
depth to be 12.5 g/L and 40 cm, respectively. The onestage
bio-vermifilter’s poor performance in removing
nitrogen and phosphorous led to several improvements in
the design of the pilot tower bio-vermifilter system
including the addition of one anaerobic biofilter for pre-treatment,
the use of two stages of bio-vermifilters, and the
replacement of gravel with ceramsite in the media. Second,
a pilot tower bio-vermifilter system built in Yixing City of
Jiangsu province showed a good performance in the
removal of chemical oxygen demand, ammonium nitrogen,
and phosphorous. However, the system’s removal of total
nitrogen showed considerable fluctuations, possibly due to
the low ratio of carbon to nitrogen in its stage two bio-vermifilter.
Finally, four operating tower bio-vermifilter
systems in three basins of China were evaluated and
compared with two other rural sewage treatment technologies
in terms of economic costs and pollutant removal
performance. Comparison results show that the tower biovermifilter
system is a versatile system that can work
effectively under a variety of natural and socioeconomic
conditions at a reasonable cost.
Keywords
Sewage; Phosphorus; Nitrogen; Chemical oxygen demand; Pollutant removal; Evaluation
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