| Earthworm-constructed wetland system with the features of "higher loading, lowerinvestment, lower energy consumption”, is appropriate for wastewater treatment inpapermaking industry. It has been primarily applied in domestic waste water treatment. Furtherresearches and developments to reinforce this system will be supportive for the sustainabledevelopment and clean production in pulp and papermaking industry in China.The literature emphasized the research on substrates, plants, earthworm and analogearthworm-constructed wetland system, which were used for CMP wastewater treatment.Different removal efficiency of different substrates (anthracite, shale, general bio-ceramic, finebio-ceramic), different plants (Reed, Cyperus alternifolius, Dracaena sanderiana) and thecombination of better plant and anthracite, the combination of earthworm and anthracite by aseries of experiments, were investigated. Then it investigated the removal efficiency of thewhole system and did researches on the degradation laws of the disposed wastewater bysubstrates, plants and the system. There were several results had been obtained and illustratedas follows:(1) When the wastewater were treated by anthracite, shale, general bio-ceramic and finebio-ceramic, the wastewater with anthracite gets the best remove of COD, then were finebio-ceramic, general bio-ceramic, the worst one was shale; the average efficiency were69.2%,59.1%,48.2%and31.5%; at the same time, the one with anthracite was also doing well in TPand chroma removal. Conmparing the removal efficiency of the four different substrates to thewastewaer, we found that the grain size, volume-weight, porosity, specific area of anthraciteare3~6mm,0.84g/cm~3,0.52%,4230m~2/m~3, which was the most one suited for microorganismto grow on and reslove organic matter.(2) Comparing the removal effects of the system with different plants: Reed, Cyperusalternifolius, Dracaena sanderiana, the results were as follow: according to the COD removal,the order of removal ability was: Dracaena sanderiana, Reed, Cyperus alternifolius; the removal of TP: Dracaena sanderiana, Cyperus alternifolius, Reed, and Dracaena sanderianawas the best plant for the remove of chorma. In the further experiment with Dracaenasanderiana and anthracite, we found the combination of Dracaena sanderiana and anthracitecould get the best removal efficiency, the COD removal was41.5%, the TP removal was98.2%,the TN removal was42.2%, the chroma removal was35.6%; the single anthracite was not thatgood for COD removal, it was only32.3%, the worst was the single Dracaena sanderiana, itwas26.3%. The results indicated that it was better for plant and substrates working together forthe pollutant remove.(3)The removal efficiency of the substrates with earthworm was better than the substrateswithout earthworm, the removal efficiency of COD, TP, TN and chroma of the group withearthworm are66.8%,.7%,71.4%and95.5%, the group without earthworm are60.3%,29.6%,55.3%, and87.2%; when HRT was20days. The group with chemical screenings was morebeneficial to earthworm than the group without chemical screenings, because chemicalscreenings could provide the earthworm with nutrition, which also brought extra pollution. Itwas important to rationalized the pavement to support earthworm and avoided new pollutionduring engineering construction.(4)It took35-40days for the analog earthworm-constructed wetland system to get stablewith HRT30days. Compared the different diposing results with different HRT:5days,10days,15days,20days,25days,30days by controlling the inflow.When the HRT was20days, theremoval efficiency were76.7%,74.5%,61.2%and79.4%, which was not obvious differentwhen HRT is30days.(5)The analog system did very well in the removing COD, TP and chroma of thewastewater. The qualities of the source water used in the experiment were: COD584mg/L, TP47mg/L, TN6.41mg/L, chroma180times, pH7.72; When the wastewater was disposed by thesystem (HRT20days), the effluent water qualities became COD136mg/L, TP12mg/L, TN2.49mg/L and chroma37times, while COD and TP was still not eligible for the nationalstandard3544-2008. According to GC-MS detection of the organic matters of the differentdisposed effluent of the system, the organic matters changed a lot in composition. There were 30different matters in the raw water, while it became14and12after plant and earthwormbiofilter, which was because most of organic substances in the effluent were able to bedecomposed into low molecular by the system disposing. |
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