Ecological Management Of Textile Dyeing Sludge

The textile industry as a pillar industry of national economy generates large amount of textile dyeing sludge. Textile dyeing sludge characterized by complicated composition, a great number of nondegradable substances, is generally difficult to be effectively disposed using conventional methods, and recycling rate is quite low. Therefore, it is very important to develop a technology of recovery and recycling of textile dyeing sludge in order to reduce the pressure on environmental pollution. Phytoremanagement was studied in this paper for advanced treatment of the textile dyeing sludge.Phytoremanagement is a new technique to clean up heavy metal-organic contaminated textile dyeing sludge which can take up heavy metal, transport and accumulate them in their above ground shoots. These plants also can decompose organic contaminants at the same time. While the mechanisms of phytoremanagement for complex contaminated textile dyeing sludge are not fully understood and the technology is not established yet. In order to solve the problem of ubiquitous polluted textile dyeing sludge, pot experiment was conducted to study phytoremanagement efficiency and mechanism of Loliumperenn L., Festuca arundinacea, Trifolium repens, Dichondra repens, Eragrostis pilosa, Cynodon dactylon, Pennisetum calndestinum, and Agrostis palustris in cleaning heavy metal-organic contaminated textile dyeing sludge. At the same time, the plant species were investigated in order to screen out native hyperaccumulators. The main results obtained were summarized as follows:By pot experiment, the influences of dyeing sludge on soil properties and turf grass growth was studied. Results indicate that textile dyeing sludge has active effects on turf grass growth, such as deepening leaf's yellow, promoting turf grass growth. The dyeing sludge contains some metal elements i.e., Cu, Cd, As, Pb and Cr, while the contents of metal elements reduces with time. Therefore, the three turfgrasses can comply to treat the textile dyeing sludge. According to the experiment, growth and clipping yields of turf grass are best in the 100% dyeing sludge treatment. The above method can be applied to the treatment of residual sludge produced in printing and dyeing wastewater biological process.Loliumperenn L., Festuca arundinacea, and Trifolium repens were screened out as feasible restoration species. The choice of plant is a very important aspect to consider in the phytomanagement-based technique for treating the textile dyeing sludge. It was reported that L. perenne was a suitable species for revegetation of metalliferous waste, producing high dry matter yields and accumulating elevated amounts of metals from reservoirs in the readily extractable and soluble forms. F. arundinacea is an cool-season turfgrass species of great economic importance. As a turfgrass, it is widely used in home lawns, parks, golf courses, playgrounds, and athletic fields. F. arundinacea can also serve as a utility turfgrass for soil solidification.By contrast, most of the researches on T. repens growing in metal-polluted areas have been focused on the symbiotic nitrogen-fixation and only few of them have been interested in metal uptake .The choice of T. repens as the third plant sample studied in this work, therefore, not only contributes to improve the knowledge about its suitability in a phytomanagement process, but also allows a comparison between the respective behaviors of a leguminous, T. repens, versus a gramineous, L. perenne and F. arundinacea, growing in textile dyeing sludge.The rotation system of Loliumperenn L.and Trifolium repens had the highest accumulation amounts to heavy metals and the best removal efficiency to organic contaminations among stubbles. Water content, ash content, and pH values were studied, together with total content of heavy metals, identification of leaching toxicity,by 10 samples in different period.All textile dyeing sludges had very high moisture levels and high ash levels, and were slightly alkaline with pH range of 7.06～8.77,indicating that these sludges belonged to slightly basic industrial wastes.This may be related to high pH of textile dyeing wastewater.Particle size distribution of textile dyeing sludge was analysed by hand according to the china standard sieves. The result obtained was: after planting of the turfgrasses the particle size distribution of textile dyeing sludge is assess to the size of the soil, so after the textile dyeing sludge can can be used in planting grass, avoiding its landfill disposal.Water content, ash content, and pH values were studied, total content of heavy metals, identification was detected by ICP-AES, by 10 samples from 10 different textile dyeing plants. All textile dyeing sludges had very high moisture levels and high ash levels, and were slightly alkaline with pH range of 7.06～8.77. The total concentrations of Fe,Al,Zn,Ni and Cu in all sludge samples were relatively higher than that of Cd and Pb with the average values of 45.99 mg·g-1,60.89 mg·g-1,0.610 mg·g-1,0.230 mg·g-1,0.3199 mg·g-1,0.040 mg·g-1 and 0.0246 mg·g-1. With respect to agricultural use tests indicated that textile dyeing sludges in the choosed examples belonged to non-hazardous wastes due to the very lower concentrations of hazardous compositions such as heavy metals than that of the state control standard.Moreover, in order to take less venture of resource utilization, it is essential to analyze the speciation of the heavy metals of Cr, Cu, Zn, Ni, Pb in further, Using Tessier A sequential extraction method. The results show that Cd is mainly in exchangeable and Fe-Mn oxides fraction, accounting for 47.6% and 23.2% respectively. So we draw the conclusion that Cd is more active, and it has potential impact on environment, so more attention should be paid to it. The other ones are relatively inert.Bioavailability of Pb, Cu, Zn, Ni and Cd was investigated with textile dyeing sludge in a pot scale experiment. Heavy metals in textile dyeing sludge and plants were analyzed after Loliumperenn L. had been grown on the textile dyeing sludge for 60 days. Chemical fractions of textile dyeing sludge were analyzed with a sequential extraction technique. The bioavailability of heavy metals decreased in the older: Cu > Zn > Pb > Ni> Cd.Textile dyeing sludge is the remains of the textile dyeing water; it did not have soil enzymes. Enzymatic activities in heavy metal polluted soil had been widely used to indicate the extent of pollution. Loliumperenn L .was used as the study crop and planted in the plastic pot. Root bags made of 300-mu nylon cloth were used to divide rhizosphere and non- rhizosphere soils. The results showed that soil enzyme activities were higher in the rhizosphere than that in the non- rhizosphere textile dyeing sludge.The four enzymes of Urease and Catalase,Polyphenol oxidase,Dehydrogenase had increased activities with increasing textile dyeing sludge application. Enzyme activity increased sharply at the beginning of the process, most likely because of the suitable availability of the organic matter in the initial mixture. It then increased smoothly from 20 to 60days, and afterwards it then decreased.Leaching tests indicated that textile dyeing sludges belonged to non-hazardous wastes due to the very lower concentrations of hazardous compositions such as heavy metals in the leachates than that of the state control standard (GB5085.3-2007, Indification of standards for hazardous wastes-Indification for extration toxicity). But each of metals in samples showed obvious different leaching behavior, possibly depending on their chemical forms. After planting, the leaching behavor was decreased. Among the three treatments, rotation system is the best phytoremanangement for the leaching toxicity on the textile dyeing sludge.Analysis of organic pollutant in textile dyeing sludge was researched. GC/MS technology was employed to examine analyze the distribution of sewage sludge. The research result showed that: types of pollutants which should be controlled preferentially in our country including benzene, toluene, nitrobenzene, phenol were detected in textile dyeing sludge. The type of the organic pollutant is few more because the treatment of the dyeing and finishing wastewater, a great number of nondegradable substances, is effectively disposed using advancedtreatment of knitting dyeing and finishing wastewater methods. After phytoremanagement by Loliumperenn L there did not detected benzene, toluene, nitrobenzene, phenol. So after planting the textile dyeing sludges in the choosed examples belonged to non-hazardous wastes.For the moment, there were no any scientific and satisfactory limits of organic pollutant in sewage sludge yet. We, therefore, suggest that the government renew the limits of it based on the heavy metals. Because of the existence of the priority of controlled organic pollutants, textile sewage sludge should be treated before resource utilization to be more effective and safer.The spectroscopic changes of textile dyeing sludge were investigated by Fourier-Transform Infrared Spectroscopy (FT-IR), The FT-IR spectra of textile dyeing sludge composed of the peaks of sorbed water, vibration of Si-O, Fe-O or Al-O. The FT-IR showed that after phytoremanagement the contents of amine and cellulose materials in textile dyeing sludge decrease and the contents of carboxyl and aromatics textile dyeing sludge also decrease.The characteristics of textile dyeing sludge are studied by the X-ray Diffraction (XRD). The analysis of XRD showed the textile dyeing sludge is clinoptilolite. The surface of textile dyeing sludge is composed of some elements, such as silicon, oxygen, aluminum and potassium, etc.