利用皇竹草处理城市污泥生产植物产品

Using hybrid giant napier to treat municipal sewage sludge and produce plant biomass

利用大生物量植物——皇竹草(Pennisetum hydridum),处理城市污泥高效生产有用的植物产品。通过小型田间试验,采用根兜分株移栽和直接扦插方式种植皇竹草,比较土壤、新鲜污泥、土壤+新鲜污泥等体积混合、植物处理后的污泥4种介质的适应性,测定了皇竹草的成活率和生长状况,以及污泥自身性质的变化;通过盆栽试验及田间试验进一步探讨育苗后移栽在新鲜污泥上的可行性。结果表明,新鲜污泥上直接扦插的皇竹草无一存活,即使是根兜分株移栽其成活率也仅为16.67%,生长较差。而对于土壤+污泥混合物或植物处理后的污泥,采用直接扦插方式,皇竹草的成活率也分别达58.33%、75.00%,两个月干草产量达22.20、19.80 t/hm2,为土壤上的5.11、4.55倍。皇竹草吸收K较明显,3个有污泥的处理皇竹草K含量接近40 g/kg干重,N、P2O5、K2O的总含量大于70 g/kg,可作为有机K肥原料;皇竹草重金属Cu、Zn、Pb、Cd含量均符合国家饲料卫生标准(GB 13078—2001),作为饲料是安全的。盆栽试验及田间试验表明,采用育苗后移栽的方式,皇竹草在新鲜污泥上的成活率达66.67%以上。因此,城市污泥直接种植皇竹草可以实现资源化利用。

Sewage sludge production is increasing greatly in China with the development of municipal wastewater treatment, and agricultural application of municipal sewage sludge （MSS） has become one of the main outlets for MSS worldwide. However, direct application of MSS and its composts to agricultural lands can lead to heavy metal contamination of soil and food. Accordingly, application of MSS to plants that are not used for food is a better alternative. Therefore, this study was conducted to investigate the use of the hybrid giant napier （Pennisetum hydridum）, which has a large biomass and can serve as animal feed or paper-making materials, to efficiently produce plant biomass while degrading MSS. To accomplish this, a field experiment composed of small plots with four treatments, soil, fresh sludge, soil-sludge mixture at a ratio of 1：1, and phyto-treated sludge, was conducted. Additionally, Giant Napier were cultivated following transplantation of ramets with roots or direct planting of cut stems. MSS was acquired from the Datansha Wastewater Treatment Plant in Guangzhou, placed in plots with a height of 20 cm on the ground and covered with permeable plastic nets. The survival and growth rate of the Giant Napier were then followed and the main characteristics of the sludge were investigated. A pot experiment and a field experiment were also conducted to investigate the feasibility of transplanting hybrid Giant Napier directly into fresh MSS using seedlings generated from stem cuttings in normal growth medium. The results showed that the hybrid Giant Napier could not survive directly in fresh MSS when cultivated from stem cuttings, as indicated by a survival rate of only 16.67%, even when transplanted ramets with roots were included in the plot. However, the plants survived and grew well in the soil-sludge mixture and phyto-treated sludge. The survival rates of stem cuttings planted in the soil-sludge mixture and phyto-treated sludge were 58.33% and 75.00%, respectively, and the yield of biomass of these two treatments ranged from 19.80 t/hm2 to 22.20 t/hm2 on a dry weight basis over two months, which was 4.55 to 5.11 times higher than that of the soil only treatment. Additionally, the hybrid Giant Napier absorbed K well, as indicated by the K content in the plant biomass reaching about 40 g/kg on a dry weight basis in the three sludge treatments. The total N, P2O5 and K2O content also reached 70 g/kg, indicating that the harvested plant biomass can be used as organic potassium fertilizer. The levels of Cu, Zn, Pb and Cd in the hybrid giant napier were below the tolerance limits of heavy metals according to the Chinese standards of feeds （GB 13078-2001）, indicating that the produced biomass was safe for use as animal feed. The pot experiment and field experiment showed that the survival rate of the hybrid Giant Napier transplanted into fresh MSS with seedlings generated from stem cuttings in normal growth medium reached more than 66.67% and the plants grew to an average of 2.6 m after 6 months. Overall, the results of this study indicate that the hybrid Giant Napier can be directly planted in fresh MSS and produce a high yield.