The effect of bioaugmentation on the performance of sequencing batch reactor and sludge characteristics in the treatment process of papermaking wastewater

In this paper, the differences between reinforced sequencing batch reactor, which was inoculated with superior mixed flora, and conventional sequencing batch reactor were compared in the process of treating papermaking wastewater under similar conditions. The results showed that the addition of superior mixed flora could not only shorten the sludge acclimation time, but also improve the treatment efficiency of reactor as well as make the reactor have higher ability to withstand high volume loading rate; the phenomenon of aerobic granulation only occurred in reinforced sequencing batch reactor, and superior mixed flora were the key reason that aerobic granular sludge could shape; aerobic granular sludge had many advantages over conventional activated sludge such as it possessed compacter microbial structure, better settling performance, and lower water content.     

Fluorescent <Emphasis Type="Italic">in situ</Emphasis> hybridization and flow cytometry as tools to evaluate the treatments for the control of slime-forming enterobacteria in paper mills

Slime formation is a serious problem nowadays in the paper industry. Some enterobacteria are associated with the formation of slime deposits in paper and board mills. Detection and characterization of slime forming bacteria, belonging to the genus Enterobacter, Raoultella, and Klebsiella have been achieved by fluorescence in situ hybridization (FISH), using one probe based on the enterobacterial repetitive intergenic consensus sequence and other two rRNA targeted oligonucleotide probes. The effects of three kinds of antimicrobiological products (biocides, dispersants, and enzymes) on these enterobacterial cells were analyzed by flow cytometry (FC). Biocides Butrol 1009 and 1072 were the most effective microbiocides against all enterobacterial cells analyzed, reaching 90% of dead bacteria after 24 h. However, the enzymatic treatment (Buzyme) was not equally efficient on enterobacteria and its microbiocide capacity varied depending on the type of microorganism. FISH and FC were effective tools to detect important slime forming enterobacteria and to select specific treatments to control microbial problems in the paper industry.     

造纸废液氧化塘纤维素酶产生菌群的分析与产酶菌株的筛选

【目的】解析造纸废液氧化塘中产纤维素酶微生物的群体组成和结构;筛选并获得一批纤维素酶产生菌,丰富菌株资源,并为纤维素酶的工业应用和环境污染的生物处理奠定基础。【方法】基于16S rRNA基因序列信息,系统考察了造纸废液氧化塘环境中产纤维素酶细菌的群体组成和结构,并通过测定纤维素酶在不同pH条件下酶活变化考察所产纤维素酶的特性。【结果】造纸废液氧化塘中产纤维素酶微生物具有丰富的多样性。在分类上分属于Firmicutes、Actinobacteria、Alpha-proteobacteria和Gamma-proteobacteria 4个门(亚门)15种。来自泥液混合样和黑液排污口泥样的产纤维素酶细菌群体多样性最为丰富,由6-7个种的细菌组成;而来自强碱性的黑液下层样品中微生物的多样性则较为贫乏,主要由来自Bacillus类细菌组成。分离菌株除酸性纤维素酶产生菌外,碱性纤维素酶和中性纤维素酶产生菌也较为丰富,且其分布与样品来源有紧密的关系。【结论】对造纸废液氧化塘产纤维素酶微生物群体组成和结构的研究,不仅有利于对新菌株资源的挖掘,也可为特殊环境的微生物学研究提供参考。     

Prediction of effluent quality in papermaking wastewater treatment processes using dynamic kernel-based extreme learning machine

Papermaking wastewater accounts for a large proportion of industrial wastewater, and it is essential to obtain accurate and reliable effluent indices in real-time. Considering the complexity, nonlinearity, and time variability of wastewater treatment processes, a dynamic kernel extreme learning machine (DKELM) method is proposed to predict the key quality indices of effluent chemical oxygen demand (COD). A time lag coefficient is introduced and a kernel function is embedded into the extreme learning machine (ELM) to extract dynamic information and obtain better prediction accuracy. A case study for modeling a wastewater treatment process is demonstrated to evaluate the performance of the proposed DKELM. The results illustrate that both training and prediction accuracy of the DKELM model is superior to other models. For the prediction of the quality indices of effluent COD, the determinate coefficient of the DKELM model is increased by 27.52 %, 21.36 %, 10.42 %, and 10.81 %, compared with partial least squares, ELM, dynamic ELM, and kernel ELM, respectively.     

Characterization of two quaternary ammonium chloride-resistant bacteria isolated from papermaking processing water and the biocidal effect on their biofilm formation

Biofilm formation and growth on equipment surfaces is detrimental to papermaking processes. However, a fundamental understanding leading to an optimal control strategy is yet to be found. Quaternary ammonium compounds (QAC) are being increasingly applied in the papermaking processes. Among them, the most frequently applied, N-alkyl-benzyl-dimethyl ammonium chloride, was employed in this study. To foster fundamental understanding of QAC efficacy towards biofilm control, two of the highest QAC-resistant strains of bacteria were isolated from the papermaking processing water and employed as model organisms. By the 16S rRNA gene sequencing technique, two Gram-negative rods with QAC resistance were identified as Morganella morganii (HB22) and the biofilm-forming Pseudomonas putida (HB45). The minimal inhibition concentration (MIC) values were 8 mg L⁻¹ for HB22 and 16 mg L⁻¹ for HB45, respectively, against QAC in basal medium (BM). However, both strains could grow under more than 150 mg L⁻¹ QAC in basal medium at neutral pH. As observed by crystal violet assay and fluorescent confocal microscopy, HB45 formed biofilm more slowly on stainless steel coupon which is the prime material of papermachine than on the surface of polystyrene, the most common material for food packaging and semi-finished/finished products. HB45 formed biofilm more slowly on stainless steel coupons than on polystyrene Petri dish surfaces, as observed by crystal violet assay and fluorescent confocal microscopy. For HB45, there was a marginal increase of inhibition of biofilm formation by increasing QAC concentration from 50 to 75 mg L⁻¹. By comparison of inhibition concentration in liquid state and in biofilm formation, the results implicate that the current practice in papermaking processes of adding biocide to qualitatively control planktonic bacterial communities does not ensure control of biofilm formation.     

Seed storage hemicelluloses as wet-end additives in papermaking

Xyloglucans and galactomannans are examples of hemicelluloses that can be accumulated in seeds of many plants, being extensively studied and used for industrial applications. Guar gum and starch are polysaccharides currently used as wet-end additives in papermaking, whereas xyloglucans have never been reported to improve paper quality. In this work we show that different types of xyloglucans improved the mechanical properties of paper sheets without affecting the optical ones. Addition of 1% (w/w) of hemicelluloses to cellulosic pulp was able to increase by about 30% the mechanical properties such as burst and tear indexes. Seeds of several species could be used as source for the production of wet-end additives, since the results did not vary with the source of polysaccharides. Even if the utilisation of these hemicelluloses will not cost less than starch or guar gum, it might represent an important strategy for sustainable use of rainforest species.