Using a high biomass plant Pennisetum hydridum to phyto-treat fresh municipal sewage sludge.

The study was carried out to investigate the use of a high biomass plant, Pennisetum hydridum, to treat municipal sewage sludge (MSS). An experiment composed of plots with four treatments, soil, fresh sludge, soil-sludge mixture and phyto-treated sludge, was conducted. It showed that the plant could not survive directly in fresh MSS when cultivated from stem cuttings. The experiment transplanting the incubated cutting with nurse medium of P. hydridum in soil and fresh MSS, showed that the plants grew normally in fresh MSS. The pilot experiment of P. hydridum and Alocasia macrorrhiza showed that the total yield and nutrient amount of P. hydridum were 9.2 times and 3.6 times more than that of A. macrorrhiza. After plant treatment, MSS was dried, stabilized and suitable to be landfilled or incinerated, with a calorific value of about 5.6MJ/kg (compared to the initial value of 1.9MJ/kg fresh sludge).

[Effect of co-planting of Sedum alfredii and Zea mays on Zn-contaminated sewage sludge].

The sewage sludge produced in Guangzhou and other cities contains heavy metals such as Zn which exceeds the national standard for agricultural use and should be taken into consideration. A phyto-treatment system consisted of metal hyperaccumulator Sedum afredii Hance and low-accumulating corn was exploited to phytoextract metals from sludge, in order to reduce heavy metals in sludge and meanwhile to stabilize the sludge and gain innocuous agricultural products. The two plants were co-cropped directly on the sludge plots, the plant biomass and metal uptake were determined as well as the changes of the treated sludge. A pot experiment was conducted to study the interaction mechanisms between the two plant roots. The results of the experiment in plots showed that the efficiency of the phyto-extraction of Zn/Cd by S. alfredii was significantly improved by co-planting and Zn content in S. alfredii reached 9 910 mgx kg(-1), 1.5 folds of that in the mono-crop. Meanwhile the produced corn grain was conformed to the national standards for foods or feeds concerning heavy metals and the treated sludge was biologically stabilized. The results from the pot experiment studying the interaction mechanisms showed that corn roots, separated from S. alfredii with a mesh barrier, decreased pH in the sludge solution, increased DOC and resulted in higher Zn/Cd concentration than that of S. alfredii mono-crop, which caused more Zn/Cd transported to the S. alfredii side and then enhanced the uptake of the heavy metals by the hyperaccumulator.

Co-cropping for phyto-separation of zinc and potassium from sewage sludge.

The use of sewage sludge as a fertilizer and soil amendment has resulted in high concentrations of heavy metals in the soil limiting its use. The present study was carried out to find the possibility of phyto-separating toxic and beneficial elements from the sludge using suitable plants. Of the five plants tested the hyperaccumulator Sedum alfredii H achieved the greatest removal of Zn, while shoots of Alocasia marorrhiza accumulated high content of K. Co-cropping these two plants on the sludge verified the previous observations on A. marorrhiza and the shoots of this plant could accumulate more than 120 g K kg(-1) dry matter in the median growth stage. Zn hyperaccumulated in Sedum's shoots to an extent more than 10 g kg(-1) dry matter; K concentrated five to ten times in the Alocasia's shoots which could be used as a good organic-K-fertilizer. Hence, the two elements were simultaneously phytoseparated and could be recycled. Furthermore, cultivation of plants in the sludge resulted in significant decreases in total Zn but kept the favorable agronomic characteristics of the sludge material, such as pH, organic matter content, and NPK concentrations and ameliorated its biological stability. These results suggest that simultaneous phyto-separation of toxic and beneficial elements from sewage sludge are possible by co-cropping using specific plants without the input of any chemicals.

[Allelopathic effects of Cymbopogon citratu volatile and its chemical components].

This paper studied the allelopathic effects of Cymbopogon citratus volatile on the seed germination and seedling growth of corn and barnyard grass (Echinochloa crusgalli) in field and in obturator, and analyzed the chemical components of the volatile with SPME and GC-MS. The results of bio-assay indicated that the germination rate of corn or barnyard grass intercropped with C. citrate or enclosed in obturator with fresh C. citratus had no significant difference from the control, but the seedling growth of corn and barnyard grass was significantly inhibited. The volatile from C. citratus roots contained 10 components. The main component was longifolene-(V4), occupying 56.67% of the total, the second component was selina-6-en-4-ol (20.03%), while the others were under 10%. There were 12 components in the volatile from C. citratus shoots. The main component was citral (53.98%), the second was z-citral (34.40%), and the others were under 4%. There were 2 monoterpenes and 9 sesquiterpenes in the volatile from shoots, and all the terpenes in the volatile from roots were sesquiterpenes. Therefore, the allelopathy of C. citratus should not be ignored when planted it with other crops.

[Laboratory-scale continuous treatment of monosodium glutamate manufacturing wastewater using yeast].

Dehydrogenation activity(DHA), test indicated that mixed yeast strains isolated from high strength monosodium glutamate wastewater could endure the high concentrations of COD, SO4(2-), and NH4+ containing in glutamate wastewater. The mixed yeast strains were inoculated to a biological contact oxidation reactor, and the reactor was used to treat the glutamate wastewater. Under a COD load ranging from 2.0 to 14.3 kg/(m3.d), the COD removal rate was over 80%. On the other hand, supplementation of phosphorus was necessary to maintain a stable COD removal performance. Variation of effluent pH seemed to have no apparent influence on COD removal rate. The optimum pH for the growth of yeast, however, was found to be in the range of 3.5-5.0. The effluent wastewater contained high concentration of yeast bodies, which could be utilized as a forage additive because of its high protein content (57.9%) and well-balanced amino acid distribution.