Treatment of Integrated Steel Plant Wastewater Using Conventional and Advanced Techniques

The integrated steel industry is considered as one of the important industrial sectors, and its outputs are inputs for other sectors including construction, engineering, medical and scientific equipment, and defence. Massive production, consumption, and export of steel signify a country's economic index. This review outlines the World's steel production quantities, the processes involved, and wastewater generation from the industry and its treatment. Wastewater generated from steel plants is highly complex and requires intensive treatment before discharge into natural water bodies. Technologies adopted for treating wastewater generated from steel industries are deliberated, focusing on coking wastewater treatment. Microbial mediated processes provide an effective means of degrading the contaminants, but the toxicity of certain compounds during higher pollutant load inhibits its further treatment. However, these processes can be integrated with either electrochemical technologies or advanced oxidation processes (AOPs), which can reduce the toxicity level. Hence, when a highly concentrated and complex mixture of contaminants is considered, an integrated approach is a resourceful option in terms of cost-effectiveness and treatment efficiency.     

The Utilization and Modeling of Photo-Fenton Process as a Single Unit in Textile Wastewater Treatment

Studies on the direct application of the photo-Fenton process (PFOP) to disinfect and decontaminate textile wastewater are rare. The output of the artificial neural network (ANN) models applied to the wastewater of a textile factory producing woven fabrics, which is used to assess the efficiency of the PFOP process, are investigated and compared with each other in this study. The highest PFOP efficiency is obtained at a pH of 3. Chemical oxygen demand (COD), suspended solids (SS) and color removal rates are 94%, 90%, and 96%, respectively. The data are modeled with ANNs and nonlinear external input autoregressive ANNs (NARX-ANN) using the MATLAB R2020a software program. Both Levenberg–Marquardt (trainlm) and scaled conjugate gradient (trainscg) algorithms are employed in the ANN and NARX-ANN models, whereas hyperbolic tangent sigmoid (Tansig) and logistic sigmoid (Logsig) functions are superimposed on the hidden layer in the ANN model, and Tansig functions are superimposed on the NARX-ANN model. It is determined that the developed ANN models are more effective in estimating the PFOP efficiency. The mean squared error is 0.000 953, and the coefficient of determination (R²) is 0.96 661.     

太湖上游流域经济发展对废水排放及入湖总磷的影响

为探索太湖流域水环境质量随经济发展的变化趋势,利用环境库兹涅茨曲线模型模拟1978-2012年太湖上游流域人均GDP与废水排放量、入湖总磷负荷的关系.结果表明:以1978年为计算基期,太湖上游流域人均GDP年均增速为10.3%~11.8%;1990-2012年,太湖上游流域年均工业废水排放量和废水排放总量分别为64799×104、93707×104t,与人均GDP均呈倒U型关系,从2006-2007年、2008-2009年呈下降趋势;入湖总磷负荷与太湖上游流域废水排放总量呈显著正相关,且与人均GDP呈倒U型关系,从2007-2008年呈下降趋势,在1990s以前为850~1200 t/a,1990s以后为1300~2000 t/a.该研究为从经济学角度评估太湖上游流域废水排放、入湖总磷负荷及其变化趋势提供科学依据.     

湖泊湿地的水质净化效应——以太湖三山湿地为例

为了解湖泊湿地的水质净化效果,以太湖三山湿地为研究对象,综合利用遥感、GIS技术、现场水质监测、实验室分析和模型模拟等方法,分析三山湿地对污染物的拦截净化效果,进而探讨湖泊湿地对水体氮、磷污染物的削减渠道及其贡献率.结果表明三山湿地对太湖水体和三山岛生活污水均有明显净化效果.2014年三山湿地的总氮(TN)、总磷(TP)输入通量分别为549.45和19.4 t,通过水草打捞/收割分别去除20.99和4.52 t,湿地水体内TN、TP变化量分别为528.46和14.88 t,这部分营养盐输出途径包括沉积到底泥、降解转化、水体交换等.湿地的TN、TP拦截能力分别为2723.56和102.48 kg/(hm2·a).水生植物收割打捞与底泥疏浚是提高湿地水质净化能力的有效措施.水动力模拟结果显示,三山湿地建成后使附近水域水体流向发生变化,流速减小,对湿地内水质产生多方面的作用.     

Typology of Municipal Wastewater Treatment Technologies in Latin America

This paper presents an analysis of the wastewater treatment plants in six Latin American and Caribbean countries. Based on a sample of 2734 municipal treatment facilities, the applied processes are classified by sizes (influent flow) and type of technologies. The distribution of the technologies is also presented for each of the six countries. In addition, a representative municipal wastewater characterization, based on influent data from 174 treatment plants, is proposed. Results show that stabilization ponds, activated sludge, and the upflow anaerobic sludge blanket reactors represent 80% of the treatment facilities of the sample, providing treatment to 81% of the total flow considered. Moreover, 67% of the plants in the sample are small (flow <25 L/s) and the very small facilities (influent flow <5 L/s) are extensively applied in the region (34% of the sample), especially in Mexico and Brazil. The use of very small treatment plants may result in low energy efficiency systems and on possible incompliance of the discharge standards. This common practice in several countries in Latin America should be revised in order to improve the environmental performance of such facilities.     

Treatment of Synthetic Olefin Plant Wastewater at Various Salt Concentrations in a Membrane Bioreactor

The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab‐scale submerged MBR with a flat‐sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na₂SO₄) (0–20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater.     

太湖水体中胶体磷含量初探

室内静态模拟不同温度下太湖15个湖区柱状沉积物磷酸根释放,分析了相应表层沉积物形态磷,以及梅梁湾间隙水中相关离子Al(Ⅲ)、Fe(Ⅱ)、Ca(Ⅱ)和PO43-含量的季节变化．研究表明,受陆源影响较大的泥区通常是太湖内源磷的稳定源;而在开敞度较大的湖区,由于表层沉积物胶体的物化吸附,使得温度对底泥磷释放的影响作用减弱,并易产生磷的“内汇”现象;在梅梁湾区成汇区,还加上春夏季藻类的局部超负荷需磷这一控制因素,从而使得太湖大部分泥区在一年中至少发生一次源-汇转换过程．化学热力学分析揭示,Al-P较之Fe-P和Ca-P更易在界面发生溶解可能是太湖表层沉积物Al-P与PO43-P释放速率呈显著相关(r=0．3858>r1-0．01,n=45)的内在原因．虽然沉积物中Fe-P有较高的释磷潜力,但浅水湖所营造的沉积物表层氧化层和广泛覆盖的无机胶体及粘土矿物的强吸附介质,可能是抑制沉积物中Fe-P释放成为优势的主要因素．估算太湖沉积物-水界面磷的净通量为899．4±573．6 t／a,约占太湖磷入湖量的1／4-1／2,其中成汇通量约为-91．2±42．4 t/a．     

Sediment resuspension under action of wind in Taihu Lake,China

A field study was undertaken to investigate the changes of the current speed, wave parameters and sediment resuspension under different wind speeds in the Taihu Lake. The Acoustic Doppler Current Profi...     

Degradation of Bezafibrate with UV/H2O2 in Surface Water and Wastewater Treatment Plant Effluent

Bezafibrate (BZF), a widely used lipid regulator, is a potential threat to ecosystems and human health in water, and the recent research showed that advanced oxidation processes (AOPs) are much more effective for BZF degradation. In this study, we investigated the photochemical decomposition of BZF in surface water and effluent from waste water treatment plants (WWTP) by UV/H₂O₂ process. The results showed that the UV/H₂O₂ process was a promising method to remove BZF at low concentration, generally at µg L^?1 level. When initial concentrations reach 100 µg L^?1 in the deionized water, >99.8% of BZF could be removed in 16 min under UV intensity of 61.4 µm cm^?2, at the H₂O₂ concentration of 0.1 mg L^?1, and neutral pH condition. Moreover, BZF degradation was inhibited in this process when humic acid (HA) and inorganic solution anions were added to the deionized water solutions, including chloride, nitrate, bicarbonate, and sulfate, significantly. In the surface water and effluent of WWTP, however, the removal efficiency of BZF was lower than that in the deionized water because of the interference of complex constituents in the surface water and effluent. Some main intermediates at the m/z range of 100–400 were observed by high performance LC‐MS (HPLC/MS) and a simple pathway of BZF degradation by UV/H₂O₂ was proposed.     

Estimation of internal nutrient release in large shallow Lake Taihu, China

Based on field investigation of wave, sediment suspension and the changes in nutrient concentration of the water column in Lake Taihu, China, we proposed two release models to quantify nutrient release under static and dynamic conditions, respectively. Under static conditions, nutrient release from sediments to the overlying water mainly depends on chemical diffusion induced by concentration gradient, in which the nutrient release is controlled by the temperature, dissolved oxygen concentration in the sediment-water interface, oxidation-reduction potential and the concentration difference between porewater and overlying water. Under dynamic condition (or disturbed condition), both dissolved and particulate nutrients in sediments are released into the water column because of wind-induced sediment suspension. The amount of nutrient release under dynamic conditions is larger than that under the static condition. The release of dissolved nutrients, however, does not increase because the wind induced turbulence made oxidation of metallic elements such as Fe (ferric iron), Mn which are capable of precipitating soluble reactive phosphate (SRP). Under dynamic conditions, therefore, the release of total phosphorus (TP) increases dramatically but the release of SRP is close to those under static conditions. In sediments of Lake Taihu, high Fe content leads to a high ratio of Fe to P contents in sediments (Fe:P ratio). Under dynamic conditions, therefore, nutrient release is controlled by the intensity of disturbance, sediment consolidation and nutrient content in sediments. As for dissolved nutrients, especially SRP, the release is also controlled by the intensity of dynamic re-oxidation, Fe content in sediments and nutrient concentration gradient between porewater and overlying water. Based on these two release modes, the release flux in Lake Taihu has been estimated. In the static condition (i.e. laboratory experimental condition), total release of NH4 -N for whole lake is ca. 10,000 ton/a, and PO43--P is ca. 900 ton/a. In the dynamic condition, nutrient release following sediment suspension was estimated according to three different intensities of wind forcing which were defined as "calm" (wind speed is less than 2 m/s), "gentle" (wind speed is greater than 2 m/s and less than 6 m/s) and "gust" (wind speed is greater than 6 m/s). The release rate in the condition of "calm" was estimated in terms of the nutrient release in the laboratory experimental static condition; whereas the release rate in conditions of "gentle" and "gust" was estimated in terms of measurement during sediment resuspension conducted in flume experiments. With the observation of wind velocity and frequency in 2001, each type of wind forcing took the frequency of 12%, 82% and 6% for "calm", "gentle" and "gust", respectively. The yearly release of nitrogen was 81,000 ton and phos- phorus was 21,000 ton, which is about 2-6 folds of annual external loading, respectively.     

Hydrodynamic-phytoplankton model for short-term forecasts of phytoplankton in Lake Taihu, China

Phytoplankton biomass is an important factor for short-term forecasts of algal blooms. Our new hydrodynamic-phytoplankton model is primarily intended for simulating the spatial and temporal distribution of phytoplankton in Lake Taihu within a time frame of 1-5 days. The model combines two modules: a simple phytoplankton kinetics module for growth and loss; and a mass-transport module, which defines phytoplankton transport horizontally with a two dimensional hydrodynamic model. To adapt field data for model input and calibration, we introduce two simplifications: (a) exclusion of some processes related to phytoplankton dynamics like nutrient dynamics, sediment resuspension, mineralization and nitrification, and (b) use of monthly measured data of the nutrient state. Chlorophyll-α concentration, representing phytoplankton biomass, is the only state variable in the model. A sensitivity analysis was carried out to identify the most sensitive parameter set in the phytoplankton kinetics module. The model was calibrated with field data collected in 2008 and validated with additional data obtained in 2009. A comparison of simulated and observed chlorophyll-α concentration for 33 grid cells achieved an accuracy of 78.7%. However, mean percent error and mean absolute percent error were 13.4% and 58.2%, respectively, which implies that further improvement is necessary, e.g. by reducing uncertainty of the model input and by an improved parameter calibration.     

太湖水体遥感反演参数的空间异质性

空间异质性的存在,会导致水质参数遥感反演中的尺度效应,影响反演精度,因此通过分析水质参数空间异质性,对于选择适当分辨率的遥感影像,提高反演精度具有重要意义.通过2008年10月在太湖布置的3个样方,利用GIS地统计学原理和分形维数的方法,对水质遥感反演中的三要素浓度,包括叶绿素a(Chl.a)、总悬浮物(TSM)和溶解有机碳(DOC)的空间异质性及其可能产生的尺度效应进行了研究.结果表明:太湖水体的三要素浓度在不同样方单元中变异系数相差较大,存在着明显的尺度效应;三个样方内Chl.a变异函数曲线斜率在变程范围内变化都较为剧烈,分形维数较高,说明太湖水体Chl.a受到某种起主导作用的生态过程的影响和控制;Chl.a和TSM的空间结构比例都在90%左右,有较强的空间相关性,表明其空间异质性的产生主要是由于结构性因素引起的,随机性因素作用微弱;DOC空间结构比例较小,说明随机性因素对其空间异质性的产生起了主导作用.三个样方中Chl.a的变程分别为147.3m、129.3m和115.0m,TSM的变程分别为1131.7m、130.6m、149.1m,因此在遥感反演中可选择TM影像,选择5×5窗口,以150m×150m作为基本单元;而DOC的变程分别为34.3m、38.5m、26.4m,表明其自相关距离较小,建议直接选择分辨率为30m的TM影像,使实际测量值与遥感影像最小单元相对应,消除反演过程中的尺度效应带来的误差.该研究也表明,MODIS的像元尺寸(250、500、1000m)明显偏大,在太湖水体三要素反演过程中,由于空间异质性引起的尺度效应,会造成一定的误差.     

太湖近代沉积物中重金属元素的累积

利用210Pb、137Cs定年技术,对来自太湖不同生态和沉积特征的三个湖区的沉积物柱状样品进行了定年,用ICP—AES分析了沉积物中重金属等元素的含量,分析了太湖沉积物中重金属的累积特征及其成因.污染较重、蓝藻水华暴发频繁的梅梁湾沉积物中的重金属含量在近25年来逐年增加;太湖上游风浪较大的夹浦湖区表层10cm沉积速率大、粒度粗,除表层1cm外,1—10cm沉积物中各种重金属含量都较低,且层间变化剧烈;下游湖区正逐渐草型化的胥口湾除表层3cm外,沉积物中重金属的含量自底层向表层大致呈不断下降的趋势.研究表明,不同年代的太湖沉积物中重金属含量差异很大,明显大于不同湖区间沉积物重金属平均含量间的差异.水动力作用引起的沉积物粒度分异很可能是影响沉积物中重金属积累的一个重要因素.总体上太湖沉积物中重金属的污染比较轻微,但已经有一定程度的Cd污染,梅梁湾沉积物中自上世纪70年代开始明显积累Cd,其他重金属元素的积累也逐渐增加,值得关注.     

太湖典型地区工矿企业废水中主要污染物排放特征研究——以江苏溧阳市为例

在调查了江苏省溧阳市化工、纺织等18家典型工矿企业废水中TN、TP、 CODMn等主要污染物质排放强度及特征基础上,估算了溧阳市工业行业的万元产值排污系数及TN、TP、CODMn的年排放量. 2000年度溧阳市全市工业行业年排放TN 479.9t, TP 40.8t, CODMn的1529.7t,约占太湖外源性污染负荷的2%-3%. 造纸、印染、化工、纺织等行业的万元产值排污系数较其它行业为高.被调查企业排污口废水中TN、TP、CODMn等污染物排放强度具有夜间高于白天等日变化特征.     

太湖蚌类现存量及空间分布格局

于2016年10月和2017年10月对太湖全湖8个湖区129个样点的蚌类进行调查,分析蚌类的物种组成、现存量、空间分布及历史变化.共采集到蚌类704个个体,隶属8属14种.全湖蚌类平均生物量和密度分别为4.169±9.337 g/m²和0.164±0.386 ind./m²;各湖区蚌类平均生物量和密度差异较大,东部沿岸区生物量和密度最高,分别为14.975±16.743 g/m²和0.577±0.758 ind./m²;湖心区生物量和密度最低,仅为0.727±1.622 g/m²和0.029±0.071 ind./m².扭蚌（Arconaia lanceolata）、圆顶珠蚌（Unio douglasiae）和背角无齿蚌（Anodonta woodiana woodiana）为太湖现阶段的优势种.基于蚌类平均密度的聚类分析,8个湖区分为3类.与历史数据相比,太湖蚌类资源呈明显衰退趋势,现状不容乐观,需加强对太湖蚌类的保护和资源的有效管理.     

太湖蓝藻水华的年度情势预测方法探讨

在太湖、巢湖、滇池、洱海、三峡水库等我国重要湖泊和水库,蓝藻水华时常发生但年际之间藻情往往有较大差异,给蓝藻水华的防控物资及人员投入、湖库水源地水质安全保障带来较大的挑战,亟待探索周年尺度的蓝藻水华强度预测方法.本文收集了太湖连续15年的蓝藻水华情势观测数据和同步的气象、水文数据用于构建蓝藻水华预测模型,提出了利用遥感反演的蓝藻水华面积(A_BL)及人工观测的水体浮游植物叶绿素α浓度([Chl.a]_LB)共同表征的蓝藻水华强度指标(BI).分析了太湖年尺度的BI值与环境条件的关系,提出了基于年初能够掌握的气象、水文、营养盐等综合环境指标进行年度BI预测的统计模型.结果表明,太湖年度BI值与冬季及初春(12-3月)日均水温(WT_12-3)、冬春季有效积温(AT_12-3)、前一年降雨总量(RF_YB)等环境因子呈显著正相关,与冬季及初春的水体总氮(TN_12-3)、溶解性总氮(DTN_12-3)、总磷(TP_12-3)及溶解性...     

Performance Evaluation of a Full‐Scale Extended Aeration System in Al‐Bireh City,Palestine

Major challenges attributed to dysfunctional wastewater treatment facilities in developing countries include lack of commitment and poor informed decision making by the higher municipal administration. This paper presents how process monitoring and control during full scale operation ensures sustainability of civic infrastructures like Al‐Bireh wastewater treatment plant (AWWTP). It is written from the perspective of practical process selection to evaluate the performance of AWWTP, a single‐sludge nitrification–denitrification process with aerobic sludge stabilization. Process monitoring data (July 2000–April 2007) from available monthly operating reports were analyzed and evaluated. Additional data on microbiological analysis and information about facility unit operations were gathered through review of published local literature and interviews with AWWTP personnel. Influent and effluent data evaluated were the chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP). Despite annual and seasonal variations in AWWTP influent for COD, BOD, TN, and TP, the Palestinian wastewater reuse requirements for restricted irrigation were met. Process design and proper facility operation have direct impacts on effluent quality. The study concludes that regardless of the design capacity and process type, adequate administrative and operational management dictate the sustainability of AWWTP and reuse schemes.