Degradation of polyacrylamide (PAM) and methane production by mesophilic and thermophilic anaerobic digestion: Effect of temperature and concentration

• PAM degradation in thermophilic AD in comparison with mesophilic AD. • PAM degradation and its impact on thermophilic and mesophilic AD. • Enhanced methane yield in presence of PAM during thermophilic and mesophilic AD. • PAM degradation and microbial community analysis in thermophilic and mesophilic AD. Polyacrylamide (PAM) is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge. Furthermore, it degrades slowly and can deteriorate methane yield during anaerobic digestion (AD). The impact or fate of PAM in AD under thermophilic conditions is still unclear. This study mainly focuses on PAM degradation and enhanced methane production from PAM-added sludge during 15 days of thermophilic (55°C) AD compared to mesophilic (35°C) AD. Sludge and PAM dose from 10 to 50 g/kg TSS were used. The results showed that PAM degraded by 76% to 78% with acrylamide (AM) content of 0.2 to 3.3 mg/L in thermophilic AD. However, it degraded only 27% to 30% with AM content of 0.5 to 7.2 mg/L in mesophilic AD. The methane yield was almost 230 to 238.4 mL/g VSS on the 8th day in thermophilic AD but was 115.2 to 128.6 mL/g VSS in mesophilic AD. Mechanism investigation revealed that thermophilic AD with continuous stirring not only enhanced PAM degradation but also boosted the organics release from the sludge with added PAM and gave higher methane yield than mesophilic AD.     

微生物法在油气勘探中的应用研究

石油天然气的微生物勘探法是通过测定土壤中以微渗漏轻烃为食物来源的微生物菌落来圈定烃类渗漏的范围.本文探讨了甲烷氧化菌、厌氧纤维素分解菌和硫酸盐还原菌在油气勘探中的意义,并将其作为指示微生物,以川西孝泉地区已知天然气田为例,对微生物油气勘查技术的试验效果进行研究.结果发现,在气田上方指示微生物存在明显异常现象,即在气田上方甲烷氧化菌、厌氧纤维素分解菌数量较少,硫酸菌还原菌较高;气田外缘甲烷氧化菌、厌氧纤维素分解菌数量较高,而硫酸菌还原菌较低.研究表明,微生物地表油气勘探技术用于油气预测是有效的.图2参12     

Optimization of phosphorus removal in uniFed SBR system for domestic wastewater treatment

The characteristic of phosphorus removal and appropriate change of the traditional operation modes were investigated in UniFed sequencing batch reactor (SBR) laboratory-scale apparatus (40 L), treating actual domestic wastewater with low ratios of C/N (2.57) and C/P (30.18), providing theoretical basis for actual application of wastewater treatment plant. UniFed SBR system with its unique operation mode had the distinct superiority of phosphorus removal. On this occasion, the effect of volumetric exchange ratio (VER) and the method of influent introduction for phosphorus removal were studied. When the carbon source became the limiting factor to phosphorus release, the higher the VER, the lower the phosphorus concentration in the effluent. Three different influent patterns, including one-time filling, four-time filling, and continuous filling with the same quantity of wastewater could increase the release rate of anaerobic phosphorus from 0.082 to 0.143 mg·P·(L·min)^-1. Appropriate change of the traditional operation modes could optimize the efficiency of phosphorus removal. When the feed/ decant time was extended from 2 h to 4 h, the phosphorous removal efficiency increased from 59.93% to 88.45% without any external carbon source. In the mode of alternation of anoxic-aerobic (A/O) condition, phosphorous removal efficiency increased from 55.07% to 72.27% clearly. The carbon source in the influent can be used adequately, and denitrifying phosphorus removal was carried out in anoxic stage 2 (A2). This mode was optimal for the treatment of actual domestic wastewater with low C/N and C/P ratios.     

Effect of acetate and propionate on the production and characterization of soluble microbial products (SMP) in aerobic granular sludge system

It is well known that soluble microbial products (SMP) derived from biological systems found in wastewater treatment plant effluent are responsible for chemical oxygen demand (COD). Aerobic granular sludge (AGS) is recognized as an efficient and innovative approach for wastewater treatment. Acetate and propionate as two dominant organic substances in wastewater need to be effectively removed before discharge. The aim of this study was to investigate the effectiveness of acetate and propionate to interfere with the accumulation, molecular weight (MW) distribution and composition of SMP in aerobic granular sludge (AGS) system using two identical sequencing batch reactors (SBR) named R1 and R2, respectively, thus reducing the COD. The results demonstrated that more SMP accumulated in R1 in presence of acetate compared to R2 treated with propionate. A positive correlation for SMP formation was detected as evidenced by aeration rates, but a negative correlation with hydraulic retention time (HRT). The MW distribution analysis suggested that small molecules (MW <3?kDa) were the dominant fraction of SMP in R1 and R2, accounting for 57–79% and 39–61%, respectively. In addition, gas chromatography-mass spectrometry (GC-MS) demonstrated that esters, alkanes, alkenes and alcohols were the predominant low-MW SMP in R1 and R2. More peaks were present in R2 (61) than R1 (46). Esters were the predominant SMP (39%) in R1, while alkanes were the predominant SMP (31%) in R2. Further, microbial community analysis indicated that more α- and γ-Proteobacteria groups which readily utilize low-MW SMP were found in R2 compared to R1-granules which may have contributed to less SMP accumulated in R2. The abundant genera in the granules were Zoogloea and Azoarcus, in particular, a greater quantity of Azoarcus was detected in R2 than R1-granules, which may be associated with higher degradation of aromatics in SMP.     

十二烷基苯磺酸钠(SDBS)及消油剂对刺参幼参的急性毒性

为探究表面活性剂对海洋棘皮动物的影响,测定了十二烷基苯磺酸钠(SDBS)和消油剂对刺参(Stichopus japonicas )幼参的急性毒性。结果显示,SDBS对刺参幼参的72 h-LC₅₀和96 h-LC₅₀分别为2.50和1.71 mg·L^-1;消油剂对刺参幼参的96 h-LC₅₀为7 498.94 mg·L^-1。刺参幼参相对于多刺裸腹溞(Moina macrocopa )和脊尾白虾仔虾(Palaemon carincauda )对SDBS的敏感性较高,相对于安氏伪镖水蚤(Pseudodiaptomus annandalei )对SDBS的敏感性则较低,SDBS对刺参幼参的毒性明显大于十二烷基磺酸钠(SDS),消油剂的96 h-LC₅₀ 远远大于SDBS和SDS,毒性非常小,但这仅是对刺参幼参而言,大多数研究忽视了消油剂自身对生物体存在的影响,因此这方面的研究工作还需要继续开展。     

A road-map for energy-neutral wastewater treatment plants of the future based on compact technologies (including MBBR)

In the paper concepts for wastewater treatment of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration. In the paper concepts for domestic wastewater treatment plants of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration.