Bacterial responses to temperature during aeration of pig slurry

The temperature effect on total anaerobic and aerobic bacterial growth in pig slurry was studied using low level batch aeration treatments. Five bioreactors were built using Plexiglas tubes to perform five temperature treatments (5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C). An airflow rate of 0.129 L/min/L manure was used to aerate manure contained in all reactors. Data showed that temperature had a profound impact on the aerobic counts in pig slurry during the aeration process. When the temperature increased from 15 degrees C to 25 degrees C, the average oxidation-reduction potential decreased from +40 mV to -60 mV, accompanied by a 75% reduction of aerobic bacteria in the manure. At 25 degrees C, the anaerobic counts were consistently higher than aerobic counts for most of days. A quadratic relationship was observed between the aerobic counts and the oxidation-reduction potential with a correlation coefficient of 0.8374. To reduce odor generation potential, the oxidation-reduction potential in the manure should be maintained at +35 mV or higher.     

Oxidation-reduction potential changes in aeration tanks and microprofiles of activated sludge floc in medium- and low-strength wastewaters.

Real-time control of aeration tank operation is key to high-efficiency pollutant removal and energy savings. One of the aims of this study was to examine the potential for using redox potential (oxidation-reduction potential [ORP]) to indicate wastewater quality online in aeration tanks treating medium (chemical oxygen demand [COD] of 70 to 150 mg/L) and low (COD of 15 to 30 mg/L) pollutant-concentration wastewaters. The field-scale data provide a good relationship between ORP values and nutrient removal along the length of the aeration tanks. The ORP values increased dramatically as organic matter was removed along the aeration tanks, indicating the improvement of the bulk liquor redox status. Dissolved oxygen higher than 1.0 mg/L was necessary for good biodegradation and improvement of the liquid redox status. Nitrification occurred at higher ORP values (380 to 420 mV) than was the case for organic substrate oxidation (250 to 300 mV). The microprofiles obtained from microelectrode measurements substantiate the heterogeneity of the microbial processes inside activated sludge flocs. Because of microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the top layer (0.1 to 0.2 mm) of the activated sludge aggregate present in medium-strength wastewater, with an anoxic zone dominating inside the flocs. When dissolved oxygen in the bulk water was higher than 4.0 mg/L, the anoxic zone inside the floc disappeared. At low wastewater pollutant concentrations, the ORP and dissolved oxygen inside the activated sludge aggregates were higher than those from medium-strength wastewater. The prospect of using ORP as an online control approach for aeration tank operation and the potential reasons for activated sludge floc size varying with pollutant strengths are also discussed.     

Quick determination of malodor-causing fatty acids in manure by capillary electrophoresis

The analysis of odor components in livestock waste has been extensively studied. Past research has identified volatile fatty acids, especially from C3 to C6, as indicators of malodor. Originally, the odorous components were analyzed by gas chromatography after a tedious absorption and troublesome extraction procedure or by a subjectively olfactory system or sense of smell. Thus, there is a need for the development of highly specific, quantitative analytical methods. In this research, a comprehensive liquid manure analysis approach-capillary electrophoresis (CE) with a systematic optimization procedure-was adopted to measure the concentration of propanoic acid (C2H5COOH, C3), butyric acid (C3H7COOH, C4), valeric acid (C4H9COOH, C5) and caproic acid (C5H11COOH, C6) in swine manure. Liquid samples after filtration were injected into CE directly. The following condition is finally proposed: fused-silica capillary, effective length 40 cm, 50 microm I.D.; buffer, 20 mM Tris and 10 mM p-anisate, pH 8.0; voltage 30 kV; temperature 25 degrees C. The results showed that CE provided a quantitative analysis of volatile fatty acids in liquid manure at the ppm level with minimum sample needed (nanoliter). Moreover, the use of CE is a timesaving technique; one measurement for the separation of those VFAs could be completed within 10 min.     

The effect of limited aeration on swine manure phosphorus removal.

Two low level aeration schemes (intermittent vs. continuous) were investigated on a laboratory scale, in conjunction with swine manure pH adjustment using sodium hydroxide (1.0 M), for manure phosphorus (P) removal. According to the data, an 80% reduction in soluble P was observed when the manure pH was increased to 8. Both intermittent and continuous aeration treatments could raise manure pH above 8 with an airflow rate of 1 L/minute in a period of 15 days. A drastic increase in pH (about 1 unit) was observed for both aeration schemes within the first day of test, resulting in a 76% reduction in soluble P concentration in the liquid. It appeared that there is no difference in terms of P removal between the two aeration programs, suggesting that the intermittent aeration be preferred to save energy while still achieving the same level of P removal.     

Preventive control of odor emissions through manipulation of operational parameters during the active phase of composting

Better understanding of the effects of key operational parameters or environmental factors on odor emission is of critical importance for minimizing the generation of composting odors. A series of laboratory experiments was conducted to examine the effects of various operating conditions on odor emissions. The results revealed that airflow rates that were too high or too low could result in higher total odor emissions. An optimal flowrate for odor control would be approximately 0.6 L/min.kg dry matter with intermittent aeration and a duty cycle of 33%. Temperature setpoint at 60°C appeared to be a turning point for odor emission. Below this point, odor emissions increased with increasing temperature setpoint; conversely, odor emissions decreased with increasing temperature setpoint above this point. With regard to the composting material properties, odor emissions were greatly affected by the initial moisture content of feedstock. Both peak odor concentration and emission rate generally increased with higher initial moisture content. Odor emission was significant only at moisture levels higher than 65%. An initial moisture level below 45% is not recommended due to concern with the resulting lower degree of biodegradation. Biodegradable volatile solids content (BVS) of feedstock had pronounced effect on odor emissions. Peak odor concentration and emission rate increased dramatically as BVS increased from 45% to 65%, thus, total odor emission increased exponentially with BVS.     

The ORP and pH profiles during simultaneous nitrification and denitrification of low carbon municipal wastewater

The ORP and pH profiles and the stability of Simultaneous Nitrification and Denitrification (SND) for low carbon municipal wastewater treatment were investigated under the different aeration modes in Sequencing Batch Reactor (SBR). The results showed that the 92% removal efficiency for TN, the smallest average level of ORP and both of the variation of ORP and pH values are achieved in Intermittent Aeration (IA) with 0.5 aeration fraction and high air-on frequency. These results suggested that IA with small aeration fraction and high air-on frequency favourable for the stable SND. The average level of ORP fluctuation range and the stability of ORP and pH values are all beneficial for the stable and complete degree of SND.     

Removal of DEHP in composting and aeration of sewage sludge

The potential of composting and aeration to remove bis(2-ethylhexyl) phthalate (DEHP) from municipal sewage sludge was studied with two dewatered sludges: raw sludge and anaerobically digested sludge. Composting removed 58% of the DEHP content of the raw sludge and 34% of that of the anaerobically digested sludge during 85 days stabilisation in compost bins. A similar removal for the anaerobically digested sludge was achieved in a rotary drum in 28 days. Less than 1% of DEHP was removed with the compost leachate. Although DEHP removal was greater from raw sludge compost than anaerobically digested sludge compost, the total and volatile solids removals were on the same level in the two composts. In the aeration of raw sludge at 20 degrees C the DEHP removals were 33-41% and 50-62% in 7 and 28 days, respectively. Both composting and aeration are concluded to have the potential to reduce the DEHP contents typically found in sewage sludges to levels acceptable for agricultural use.     

抗生素杆菌肽锌对鸡粪厌氧水解酸化的影响

以上海某养鸡场产生的粪便为研究对象,探讨抗生素杆菌肽锌(ZnBc)对鸡粪厌氧水解酸化的影响。结果表明:(1)相比于发酵前的pH,发酵后的pH变化幅度不大,在6.65～7.40变化。(2)氨氮和ZnBc浓度对数(lgc)呈负线性相关,经拟合方程测算出ZnBc对氨氮的半抑制常数(IC50)为15.23mg/L。当ZnBc>5 105mg/L时,氨氮的产生完全受抑制。添加ZnBc对发酵液氨氮的影响极显著。(3)溶解磷(SP)和lgc满足Boltzman方程。添加ZnBc对发酵液SP的影响极显著。(4)ZnBc不仅影响挥发性脂肪酸(VFAs)浓度,还影响VFAs组分。(5)添加ZnBc对发酵液总有机碳(TOC)有极显著影响。(6)相比原鸡粪,发酵后固体有机N、C、H均下降,并分别在ZnBc为0.10、0.01、0.01mg/L时达到最低值,说明鸡粪在厌氧水解酸化过程中固体有机组分向液体转移。     

Effects of anaerobic selector hydraulic retention time on biological foam control and enhanced biological phosphorus removal in a pure-oxygen activated sludge system.

Increased anaerobic selector hydraulic retention times (HRTs) in a high-purity oxygen activated sludge process resulted in an increase in soluble orthophosphate release and biodegradable chemical oxygen demand removal, confirming that enhanced biological phosphorus removal occurs at aeration solids retention times (SRTs) below 1.7 days. Under operating conditions that included biological foam trapping and recycling, an anaerobic selector with HRTs higher than 55 minutes resulted in a decrease in filament counts and effective foam control. Effective norcardioform control is achieved through the combination of metabolic selective pressure and increased soluble organic substrate removal in the anaerobic selector and low aeration SRT.     

混合水解对打捆麦秸水解产酸的影响

为研究混合水解对麦秸水解产酸的影响,以猪粪、厨余和蔬菜废物为原料,研究其分别与麦秸混合水解产酸的特性,分析了水解过程中pH值、COD、SCOD和VFAs的变化。结果表明,除麦秸＋蔬菜废物最佳出料时间为3～9d外,麦秸、麦秸＋厨余垃圾、麦秸＋猪粪水解液最佳出料时间均为3～7d,7d后水解液COD浓度下降;将蔬菜废物与麦秸混合水解,水解液pH值降低幅度最大,水解液中总有机酸浓度最高,pH值最低为5．31,有机酸浓度最高达6．46g／L,且水解液中SCOD浓度、SCOD／COD比值最大;添加猪粪明显促进了麦秸有机物的水解溶出,麦秸单位干物质水解率和产酸率较对照分别提高了43％～134％和50．53％,但对提高水解液SCOD浓度、SCOD／COD比、TVFA浓度、降低水解液pH值的效果不如蔬菜废物;添加厨余垃圾的效果介于猪粪和蔬菜废物之间。从促进麦秸水解产酸的角度,以添加猪粪的效果最好。     

Precipitation of swine and cattle manure phosphorous using limestone dust

The effectiveness of SPS and PULPRO, fine limestone dusts, in precipitating swine and dairy manure phosphorous (P) was determined in the laboratory. Both manures were sieved before being treated with limestone, to reproduce the treatment of mechanically separated manure and to observe the precipitation effect of limestone without that of the large manure solid particles. P precipitation was optimized by varying precipitation conditions (propeller blade speeds, mixing time and limestone levels) and limestone particle size. P precipitation was optimized using a propeller blade mixing speed of 0.3 m s(-1) for at least 5 minutes, using 3% limestone (dry limestone mass over wet manure mass). In terms of particle size, PULPRO 20 (limestone with a particle size of 0.02 mm) produced the most P precipitation and the smallest volume and mass of sludge, as compared to PULPRO 10, PULPRO 3 and SPS (limestone with a particle size of 0.01, 0.003 and 0.3 to 0.003 mm, respectively). For both 9.5% TS (total solids) dairy and 8.8% TS swine manure, mechanical separation followed by limestone precipitation concentrated 90% of manure TS and TP in a sludge volume representing 45% of the initial raw manure mass.     

Settling characteristics of nursery pig manure and nutrient estimation by the hydrometer method

The hydrometer method to measure manure specific gravity and subsequently relate it to manure nutrient contents was examined in this study. It was found that this method might be improved in estimation accuracy if only manure from a single growth stage of pigs was used (e.g., nursery pig manure used here). The total solids (TS) content of the test manure was well correlated with the total nitrogen (TN) and total phosphorus (TP) concentrations in the manure, with highly significant correlation coefficients of 0.9944 and 0.9873, respectively. Also observed were good linear correlations between the TN and TP contents and the manure specific gravity (correlation coefficients: 0.9836 and 0.9843, respectively). These correlations were much better than those reported by past researchers, in which lumped data for pigs at different growing stages were used. It may therefore be inferred that developing different linear equations for pigs at different ages should improve the accuracy in manure nutrient estimation using a hydrometer. Also, the error of using the hydrometer method to estimate manure TN and TP was found to increase, from +/- 10% to +/- 50%, with the decrease in TN (from 700 ppm to 100 ppm) and TP (from 130 ppm to 30 ppm) concentrations in the manure. The estimation errors for TN and TP may be larger than 50% if the total solids content is below 0.5%. In addition, the rapid settling of solids has long been considered characteristic of swine manure; however, in this study, the solids settling property appeared to be quite poor for nursery pig manure in that no conspicuous settling occurred after the manure was left statically for 5 hours. This information has not been reported elsewhere in the literature and may need further research to verify.     

Odor compounds released from different zones of two adjacent waste treatment facilities: Interactive influence and source identification

An integrated approach was applied to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities (an aerobic biological treatment plant and an anaerobic landfill site), identify their precise sources, and distinguish the interactive influences between them. Seven odor families were investigated, including alcohols, terpenes, carbonyls, aromatics, volatile fatty acids (VFAs), sulfur compounds, and ammonia. Principal components analysis, characteristic molecular ratios, and ternary diagrams were used to differentiate the interactive influence of the odor sources. Among typical biotic compounds, terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs. Ratios of p-cymene at sampling locations related to the biological treatment plant (aerobic status) were between 0.00 and 0.25, whereas those at landfill-related sampling points (anaerobic status) were between 0.25 and 1.0. The molecular ratio of terpenes was also found to be an appropriate means to differentiate between homologous and similar odor sources such as an aerobic biological treatment plant and anaerobic landfill.

Implications:?The aim of this work is to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities, identify their precise sources, and distinguish the interactive influences between them. The emission of gaseous pollutants greatly affects the living quality of nearby residents, and odor complaints are becoming a major problem. In this study we utilized various pretreatment and analytical methods to obtain integrated emission information of gaseous pollutants. The results showed terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs.     

Odor measurements for manure spreading using a subsurface deposition applicator

Odor emissions during manure spreading events have become a source of concern, particularly where farms are located nearby urban areas. The objective of the present study was to compare odor concentrations and odor emission rates due to pig manure application using two different types of applicators, a sub-surface deposition system and a conventional splash-plate applicator. Air samples were collected using a Surface Isolation Flux Chamber and the "bag-in-vacuum chamber" techniques, at 0.5, 1.5 and 2.5 hours after manure application. A three-station forced-choice dynamic dilution olfactometer was used by an odor panel for determining odor concentration. Preliminary results indicated that with the sub-surface deposition system applicator odor emission rate was reduced by 8% to 38% compared to that of the conventional splash-plate applicator. The highest reduction in odor strength and odor emission rate was observed in the most offensive period after manure application. The sub-surface deposition system may be a solution for hog producers who wish to reduce odor complaints from applying manure without the cost and problems associated with deep injection systems.     

Influence of temperature and time on phosphorus removal in swine manure during batch aeration

This study was conducted to investigate the effects of temperature and time on the mechanisms of phosphorus removal in swine manure during aeration. Removal of soluble orthophosphates significantly increased with aeration time and temperature. Successive significant ortho-P removals were observed between days one and nine but no significant additional removals were recorded thereafter. Removals were significantly higher at temperatures of 20 and 25 degrees C than at temperatures of 5, 10, and 15 degrees C and ranged between 22.9 to 31.0%. Insoluble inorganic phosphorus also changed significantly with aeration time and temperature and with a similar trend as soluble orthophosphates. The pH of the manure explained 92 and 87% of the content of insoluble inorganic phosphorus at lower temperatures (5, 10, 15 degrees C) and at higher temperatures (20, and 25 degrees C), respectively. Organic phosphorus and aerobes growth patterns were similar to that of soluble orthophosphates removal. The rapid growth of aerobes was most probably the principal factor behind a rapid soluble ortho-P removal above 15 degrees C. The contribution of inorganic phosphates to the removal of soluble orthophosphates was approximately 61% while that due to organic P was approximately 35%. Precipitation was found to be the principal mechanism governing removal of soluble ortho-P in swine manure during aeration treatments.     

问歇曝气周期对低C/N比污水生物脱氮的影响

研究了间歇曝气生物脱氮工艺中,曝气周期和污水的c/N比对脱氮效率的影响,以及氧化还原电位(ORP)变化规律.中试试验结果表明,TN污泥负荷为0.05 kg/(kg MLVSS.d)时,间歇曝气系统的硝化反应所需曝气时间与总反应时间比至少要在0.5以上,一周期内搅拌时间不宜超过1 h;反硝化过程中难以找到ORP曲线突变点,因此,在低c/N比污水生物脱氮中ORP难以作为工程控制参数;由于原水的碳氮比太低,TN去除率只有35%～40%左右,为提高脱氮效率有必要投入外加碳源.     

Microwave treatment and struvite recovery potential of dairy manure

Microwave digestion of liquid dairy manure was tested for the release of nutrients, such as orthophosphates, ammonia-nitrogen, magnesium, calcium and potassium, both with and without the aid of an oxidizing agent (hydrogen peroxide). The orthophosphate to total phosphorus ratio of the manure increased from 21% to greater than 80% with 5 minutes of microwave treatment. More than 36% of total chemical oxygen demand (t-COD) of the manure was reduced when microwave digestion was assisted with peroxide addition. In addition, the volatile fatty acids (VFAs) distribution shifted to simpler chain acids (acetic acid in particular) with an increase in operating temperature. In the second part of the study, digested manure with increased soluble phosphate was tested for the recovery of struvite (magnesium ammonium phosphate) at different pH. It was found that up to 90% of orthophosphate can be removed from the solution. Overall, it was concluded that the oxidizing agent-assisted microwave digestion process can be used upstream of anaerobic digestion, following which the anaerobically digested manure can be used for struvite recovery. Thus, this microwave digestion process presents the potential for enhanced efficiencies in both manure digestion and struvite recovery.     

准好氧填埋氮转化影响因子变化规律试验研究

依据准好氧填埋工艺原理建立了试验装置,定期监测渗滤液硝氮、氨氮、温度、pH值、氧气含量,ORP(氧化还原电位),研究准好氧填埋过程中氮转化的影响因子变化规律.结果表明,温度呈现先上升后下降再回升的变化趋势;pH值呈现出先上升再下降的变化趋势,最大值达到8.74,之后下降到7.91.填埋开始阶段,填埋层的氧气浓度缓慢下降,最低下降到3.43%,随着空气经导气管和渗滤液收集管进入填埋体,氧气浓度明显上升达到10.46%.进入填埋后期,氧气浓度再次下降,最低到1.61%.填埋试验后期,ORP均小于150 mV,最大值为123 mV,最小值为-166 mV.