Operational guidance for aeration and flow augmentation for the Chicago Area Waterway System—A case study

The Chicago Area Waterway System (CAWS) is a 133.9 km branching network of navigable waterways controlled by hydraulic structures, in which the majority of the flow is treated wastewater effluent and there are periods of substantial combined sewer overflows. The CAWS comprises a network of effluent dominated streams. More stringent dissolved oxygen (DO) standards and a reduced flow augmentation allowance have been recently applied to the CAWS. Therefore, a carefully calibrated and verified one-dimensional flow and water quality model was applied to the CAWS to determine emission-based real-time control guidelines for the operation of flow augmentation and aeration stations. The goal of these guidelines was to attain DO standards at least 95% of the time. The “optimal” guidelines were tested for representative normal, dry, and wet years. The finally proposed guidelines were found in the simulations to attain the 95% target for nearly all locations in the CAWS for the three test years. The developed operational guidelines have been applied since 2018 and have shown improved attainment of the DO standards throughout the CAWS while at the same time achieving similar energy use at the aeration stations on the Calumet River system, greatly lowered energy use on the Chicago River system, and greatly lowered discretionary diversion from Lake Michigan, meeting the recently enacted lower amount of allowed annual discretionary diversion. This case study indicates that emission-based real-time control developed from a well calibrated model holds potential to help many receiving water bodies achieve high attainment of water quality standards.     

Feasibility of controlling nitrification in predenitrification plants using DO, pH and ORP sensors.

Experimental studies were carried out on a bench-scale nitrogen removal system with a predenitrification configuration to gain insights into the spatial and temporal variations of DO, pH and ORP in such systems. It is demonstrated that these signals correlate strongly with the operational states of the system, and could therefore be used as system performance indicators. The DO concentration in the first aerobic zone, when receiving constant aeration, and the net pH change between the last and first aerobic zones display strong correlations with the influent ammonia concentration for the domestic wastewater used in this study. The pH profile along the aerobic zones gives good indication on the extent of nitrification. The experimental results also showed a good correlation between ORP values in the last aerobic zone and effluent ammonia and nitrate concentrations, provided that DO in this zone is controlled at a constant level. These results suggest that the DO, pH and ORP sensors could potentially be used as alternatives to the on-line nutrient sensors for the control of continuous systems. An idea of using a fuzzy inference system to make an integrated use of these signals for on-line aeration control is presented and demonstrated on the bench-scale system with promising results. The use of these sensors has to date only been demonstrated in intermittent systems, such as sequencing batch reactor systems.     

Improvement of oxygen transfer efficiency in aerated ponds using liquid-film-assisted approach.

In aerated ponds, oxygen is generally supplied through either diffused or mechanical aeration means. Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, a liquid-film-forming apparatus (LFFA) is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for LFFA alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for the liquid film aeration system increases by 37% in comparison with a conventional aeration system. Additionally, by tuning finely the structural parameters of the LFFA, it can also lead to high dissolved oxygen (DO) water with the DO percent saturation greater than 90%. More importantly, this result is accomplished by simply offering a single-pass aeration at a depth as shallow as 26 cm. As a result, the objective of economical energy consumption in aerated ponds can be realized by lowering the aeration depth without sacrificing the aeration efficiency. It is noteworthy that the data presented in this study are acquired either numerically or experimentally.     

曝气对过饱和溶解氧消散过程影响的试验研究

为了促进曝气技术在减缓过饱和溶解氧(DO)影响中的应用,设计开展了无曝气工况和曝气工况下的过饱和DO释放试验,研究了曝气对过饱和DO消散过程的影响规律,分析了不同曝气条件下过饱和DO的释放过程和释放系数。试验结果表明,曝气能显著促进过饱和DO的消散,曝气工况下DO饱和度从170%左右消散至105%左右所需时间均小于11 min,而无曝气工况下所需时间最少为240 min；过饱和DO释放系数随曝气量的增大而增大,随曝气水深的增大而减小,与曝气孔径呈现较强的负相关幂函数关系。根据曝气对过饱和DO的释放规律建立了过饱和DO释放系数与曝气条件的定量关系,通过量纲分析建立了过饱和DO释放系数与曝气条件、模型尺寸、流体参数之间的定量关系,两种定量关系中,后者的均方根误差和平均绝对误差较小、相关系数较高,且参数较易获取,因此实用性更好。     

绍兴市饮用水源汤浦水库水质特征研究

饮用水库的水质保护是优质供水的前提保障.通过对汤浦水库各类水质指标连续5年的系统监测,详细分析了一些变化比较敏感,并对水源保护和供水水质具有较大影响的pH、DO、CODMn、TN、TP、藻类等指标的现状、特征及发展趋势,为饮用水库的水质管理及供水处理提供了理论指导.同时,评价了汤浦水库的富营养化状况,提出了饮用水库水质监测、评价的方向和建议.     

Prediction of dissolved oxygen content changes based on two-dimensional behavior features of fish school and T–S fuzzy neural network

Dissolved oxygen (DO) content is an important index of river water quality. Water quality sensors have been used in China for urban river water monitoring and DO content prediction. However, water quality sensors are expensive and difficult to maintain, and have a short operation period and difficult to maintain. This study developed a scientific and accurate method for prediction of DO content changes using fish school features. The behavioral features of the Carassius auratus fish school were described using two-dimensional fish school images. The degree of DO content decline was graded into five levels, and the corresponding numerical ranges of cluster characteristic parameters were determined by considering the opinions of ichthyologists. Finally, the variation of DO content was predicted using the characteristic parameters of the fish school and the multiple-input single-output Takagi–Sugeno fuzzy neural network. The prediction results were basically consistent with the actual variations of DO content. Therefore, it is feasible to use the behavioral features of the fish school to dynamically predict the level of DO content in water, and this method is especially suitable for prediction of sharp decline of DO content in a relatively short time.     

Nitrite accumulation by aeration controlled in sequencing batch reactors treating domestic wastewater.

The feasibility of obtaining and keeping stable nitrite accumulation in Sequencing Batch Reactors (SBRs) treating domestic wastewater is studied. The final product of ammonium oxidation is either reproducible nitrate or nitrite depending on the aeration strategy. With the aerobic-anoxic sequence, two SBRs fed with domestic wastewater are operated in parallel. One SBR (SBR1) is controlled by the aeration control strategy, and the other SBR (SBR2) by alternate aeration control strategy. Based on the on-line indirect measurements of DO and pH, the relationship between pH (or DO) and nitrogen concentration (NH4+-N, NO(3-)-N and NO(2-)-N) is investigated. The result indicates that pH and DO can be used as control parameters for the real-time aeration control strategy to obtain nitritation in SBR treating domestic wastewater. The result of SBR1 indicates that long-term stable nitritation is possible at 32+/-1 degrees C. The result of SBR2 indicates that the aeration control strategy is necessary for nitritation during the acclimation period, because the nitrite accumulation disappears when the aeration is extended.     

A control strategy for reducing aeration costs during low loading periods.

The efficiency of the aeration system in a full-scale activated sludge basin with 3 separately controlled aeration zones was improved for the low loading period in summer. The air flow rate to each aeration zone is currently regulated to hold a preset dissolved oxygen concentration (DO). Four different DO setpoint combinations were tested, each one for a one week period, using dynamic off-gas testing to measure the standardised oxygen transfer efficiency (alphaSOTE). As the DO setpoints were lowered, the total air flow rate to the basin decreased initially. A low DO in the first zones slowed biomass activity and pushed the load towards the end of the aeration basin. The relationship between alphaSOTE and the specific diffuser flow rate qD is different for each zone. In Zone 1 there was a strong decrease in alphaSOTE as qD increased, while Zones 2 and 3 were fairly independent of qD, Zone 2 at a higher level than Zone 3. Aeration costs were reduced by 15% for the most efficient combination. To achieve even more savings, a control strategy adjusting oxygen transfer rates over the aeration basin to the necessary oxygen transfer rates is suggested. It is based on changing the DO setpoints to reach the lowest total air flow rate while meeting the effluent requirements.     

曝气条件对侧流活性污泥水解工艺脱氮性能和微生物的影响

通过改变传统厌氧/缺氧/好氧（A²/O）反应器和侧流活性污泥水解（SSH）反应器的曝气强度和溶解氧（DO）浓度,考察了曝气条件对脱氮性能的影响,并对比研究了微生物群落结构的变化规律。结果表明：相较于高DO阶段,两组反应器在中低DO阶段有更好的脱氮效果。在相同进水条件下,SSH反应器的脱氮性能优于A²/O反应器,且出水满足一级A标准。高通量测序结果表明,中低DO浓度更有利于脱氮微生物的生长。相对于A²/O反应器,SSH反应器中反硝化微生物的相对丰度更高。因此,合理控制曝气条件维持中低DO浓度有利于SSH工艺达到良好的脱氮性能及脱氮微生物的生长。     

Aeration tank odour by dimethyl sulphoxide (DMSO) waste in sewage.

Sewage plants can experience dimethyl sulphide (DMS) odour problems by at least one mg/L dimethylsulphoxide (DMSO) waste residue in plant influent, through a DMSO/DMS reduction mechanism. This bench-scale batch study simulates in bottles the role of poor aeration in wastewater treatment on the DMSO/DMS and sulphate/H2S reduction. The study compares headspace concentrations of sulphide odorants developed by activated sludge (closed bottles, half full) after six hours under anoxic versus anaerobic conditions, with 0 versus 2 mg/L DMSO addition. Anoxic sludge (0.1 - 2 mg/L dissolved oxygen, DO) with DMSO resulted in about 50 ppmv DMS and no other sulphide, while DMSO-free sludge was free of detectable sulphides. Anaerobic sludge (no measurable DO to the point of sulphate reduction) with DMSO resulted in 22/4/37 ppmv of H2S/methanethiol (MT)/DMS, while DMSO-free sludge resulted in 44/8/2 ppmv of H2S/MT/DMS. It is concluded that common "anoxic" aeration tank zones with measurable DO in bulk water but immeasurable DO inside sludge flocs (nitrate reducing) experience DMSO reduction to DMS that is oxidation resistant and becomes the most important odorant. Under anaerobic conditions, H2S from sulphate reduction becomes an additional important odorant. A strategy is developed that allows operators to determine from the quantity of different sulphides whether the DMSO/DMS mechanism is important at their wastewater plant.     

河道曝气技术在苏州地区河流污染治理中的应用

根据河道曝气技术控制河流水环境污染的基本原理以及在国内外的应用进展,结合苏州河流污染的实际情况,分析了在苏州地区利用河道曝气技术的可能性、可行性。针对苏州河道的特征,应选用相应的模型来计算需氧量并选择不同的充氧设备进行曝气复氧,同时配合多种措施来提高河道曝气复氧的效果。合理运用河道曝气技术可以快速提高溶解氧、改善水体黑臭现象、净化水质,在苏州这样的河网城市具有较为广阔应用前景。     

Modeling the Linkage Between River Water Quality and Landscape Metrics in the Chugoku District of Japan

The present study was conducted using secondary database, remote sensing, geographical information system (GIS) and multivariate analysis tools in order to develop Multiple Linear Regression (MLR) models that could be able to predict level of water quality variables using compositional and spatial attributes of land cover in the river basins. The study encompasses 21 river basins with 32 000 Km² area, located in the Chugoku district in West Japan. Biological Oxygen Demand (BOD), pH, Dissolved Oxygen (DO), Suspended Solid (SS), Total Nitrogen (TN), and Total Phosphorus (TP) were considered as water quality variables of the stream. Satellite data was used to generate the land cover map of the study area. MLR models were developed using the compositional (%) and spatial attributes (landscape metrics) of the land cover at watershed and class levels for representing the land cover-stream water quality linkage. The results of the MLR modeling using the land cover data at the class level revealed that 92%, 74% and 62% of the total variations in concentration of DO, pH and TP were explained by changes in the measure of the spatial attributes of the land cover at the class level in the study area. These models can help local and regional land managers to understand the relationships between the compositional attribute (%) and the spatial features of the land cover and river water quality and would be applied in formulating plan for watershed-level management.     

Restoration of hypolimnetic dissolved oxygen through light irradiation-induced periphyton production

Large quantities of detritus can accumulate on the bottom sediments of eutrophic lakes, leading to depletion of dissolved oxygen (DO) in the hypolimnion. Decreased redox potential associated with low hypolimnetic DO concentrations can accelerate the remobilization of ammonia and phosphorus from the sediments back into the water column. As maintenance of aerobic conditions in the hypolimnion is an important consideration for successful lake management, this research focused on the use of periphyton production of DO to control hypolimnetic DO levels. To augment periphyton photosynthesis, light was irradiated to the bottom sediments via glass fibres, in order to examine the effects of light irradiation on DO restoration on bottom sediments in test chambers. Dissolved oxygen restoration by periphytic photosynthesis was confirmed in these experiments, with both temperature and light intensity having positive effects on the areal net oxygen production rate. The Q ₁₀ temperature coefficient for net oxygen production was estimated to be 2.24. In typical temperate-zone lakes, the hypolimnetic water temperature is <15 °C, resulting in an expected areal net oxygen production rate ranging from 100 to 200 mg O₂ m⁻² day⁻¹ at a light irradiation of 50 μE m⁻² s⁻¹. Based on these experimental results, the condenser area required to achieve DO restoration under hypolimnetic light irradiation alone was estimated to be 3.2–4.1% of the hypolimnetic area. Thus, hypolimnetic light irradiation combined with hypolimnetic aeration can reduce energy consumption required for hypolimnetic aeration in DO restoration efforts.     

Evaluation,prediction, and protection of water quality in Danjiangkou Reservoir,China

The water quality in the Danjiangkou Reservoir has attracted considerable attention from the Chinese public and government since the announcement of the Middle Route of the South to North Water Diversion Project(SNWDP), which commenced transferring water in 2014.Integrated research on the evaluation, prediction, and protection of water quality in the Danjiangkou Reservoir was carried out in this study in order to improve environmental management. Based on 120 water samples, wherein 17 water quality indices were measured at 20 monitoring sites, a single factor evaluation method was used to evaluate the current status of water quality. The results show that the main indices influencing the water quality in the Danjiangkou Reservoir are total phosphorus(TP), permanganate index(COD Mn), dissolved oxygen(DO), and five-day biochemical oxygen demand(BOD5), and the concentrations of TP, BOD5, ammonia nitrogen(NH3e N), COD Mn, DO, and anionic surfactant(Surfa) do not reach the specified standard levels in the tributaries. Seasonal Mann e Kendall tests indicated that the COD Mn concentration shows a highly significant increasing trend, and the TP concentration shows a significant increasing trend in the Danjiangkou Reservoir. The distribution of the main water quality indices in the Danjiangkou Reservoir was predicted using a two-dimensional water quality numerical model,and showed that the sphere of influence from the tributaries can spread across half of the Han Reservoir if the pollutants are not controlled.Cluster analysis(CA) results suggest that the Shending River is heavily polluted, that the Jianghe, Sihe, and Jianhe rivers are moderately polluted, and that they should be the focus of environmental remediation.     

泉州山美水库水质富营养化评价分析与防治对策

根据山美水库2008-2011年的水质监测资料,通过"卡尔森指数法"对水库富营养化现状进行评价。研究山美水库入库、库中及出库表层的水质特征、富营养化程度及富营养化变化趋势,并进行成因分析。结果表明:从入库、库中至出库的表层水体,TP浓度较高,TN超标最为严重,DO值在2011年相对较低,其他指标均满足水库水质Ⅱ类标准。四年中的水库富营养化程度基本为中营养状态,并有向中富营养转变的趋势。进行了成因分析并提出防治富营养化的相关对策与措施,以改善山美水库的水质情况。     

池塘底部微孔曝气增氧试验及分析

随着水产养殖产业的持续升温、养殖密度的提高和高产高效养殖技术的推广,增氧装备越来越成为水产养殖必不可少的设备。鼓风曝气系统中的微孔曝气式增氧机因其曝气效率相对较高,适应性较强而广泛应用于水产养殖中。为了更好地了解和推广使用微孔曝气增氧系统,本文通过室内模型试验及数据分析,研究了曝气流量与曝气管长度对总氧体积传质系数的影响,构建了总氧体积传质系数预测模型。因此,本文的研究能为微孔曝气增氧系统在实际中的应用提供有价值的参考。     

Potential of OUR and OTR measurements for identification of activated sludge removal processes in aerated basins.

In order to develop a process control scheme to reduce energy costs for aeration in activated sludge systems with biological P removal, pre-denitrification and nitrification stages, the spatial distribution of carbon oxidation and nitrification was evaluated over a long full-scale plug flow aeration basin using an externally measured specific oxygen uptake rate (sOUR) and in basin measurement of the actual specific oxygen transfer rate (sOTR) with off-gas testing as well as with the calculated oxygen demand from NH4-N concentrations (sOTR(N)). Using a simple static model, a gas phase balance on oxygen and carbon dioxide, sOTR(N) values were also calculated from off-gas testing. Comparison of sOTR(N) to sOTR and sOUR for carbon oxidation (sOUR(C)) to nitrification (sOUR(N)) at different loading conditions allowed the oxidation processes to be followed over the three zones of the aeration basin. As expected, the distribution depended on the dissolved oxygen concentration (DO) in the basin. However, the major change was in the C-oxidation rate and not the nitrification rate. At a low DO, and when NH4-N was present in the zone, the amount of oxygen transferred for nitrification was nearly the same, but the overall sOTR was lower. The externally measured sOUR was only useful when it was differentiated into sOUR(N) and sOUR(C). sOUR(N) could be used to predict the nitrification rate in the basin. With further refinement, the gas phase balance model has potential to be used to monitor the degree of nitrification over the basin length. This can be integrated into a control scheme to reduce aeration costs by adjusting the DO setpoint according to loading conditions in the     

南水北调工程对衡水湖水环境的影响预测

利用2003年衡水湖水体溶解氧和氨氮浓度的实测数据对环境流体动力学模型EFDC的计算结果进行的验证结果表明,EFDC模型可以应用于衡水湖的水环境模拟。该模型预测南水北调工程对衡水湖水环境影响的结果表明,水温受水深、大气温度和调水温度的影响,而溶解氧浓度主要受水温影响;调水期不同的调水方式对湖内的污染物浓度变化有一定影响,调水结束后扩散作用使湖内的污染物浓度趋于一致。为了能够容纳南水北调来水,增容势在必行。建议将衡水湖挖深,这样既可扩充湖的容量,也可将污染物含量高的底泥挖除,使水质不易变坏。     

关于现行再生水水质标准和规范执行情况的讨论

针对现行再生水水质标准、规范的执行情况进行了讨论,提出了再生水回用于工业循环冷却水时氨氮浓度控制在5 mg/L以下,应根据现实情况近期适当降低某些城市河道的水体功能,在《城市污水再生利用城市杂用水水质》中列入部分能够全面反映水质安全的关键性指标,城市公共再生水尽量采用统一供水水质等一系列建议.