Intended process water management concept for the mechanical biological treatment of municipal solid waste

Accumulating operational experience in both aerobic and anaerobic mechanical biological waste treatment （MBT） makes it increasingly obvious that controlled water management would substantially reduce the cost of MBT and also enhance resource recovery of the organic and inorganic fraction. The MBT plant at Gescher, Germany, is used as an example in order to determine the quantity and composition of process water and leachates from intensive and subsequent rotting, pressing water from anaerobic digestion and scrubber water from acid exhaust air treatment, and hence prepare an MBT water balance. The potential of, requirements for and limits to internal process water reuse as well as the possibilities of resource recovery from scrubber water are also examined. Finally, an assimilated process water management concept with the purpose of an extensive reduction of wastewater quantity and freshwater demand is presented.

Dechlorination Behavior of Mixed Plastic Waste by Employing Hydrothermal Process and Limestone Additive

The usage of plastic-impregnated waste derived solid fuel in conventional combustor is hindered by many technical factors, especially its organic chlorine content. In this paper, experimental study of hydrothermal treatment on mixed plastic waste using the mixture of polypropylene, polystyrene, polyethylene and polyvinyl chloride （PVC） has been performed to observe the dechlorination effect of hydrothermal treatment on the waste. The system was generally applying saturated steam at around 2.4 MPa in a stirring reactor for about 90 minutes. After undergoing the process, the organic chlorine in treated plastic waste was reduced to 1,700 ppm level while the inorganic chlorine content was increased, suggesting an organic chlorine conversion phenomenon to inorganic chlorine, accompanied with low pH due to dehydrochlorination process. Additional limestone （Ca（OH）2） in subsequent experiment showed that the similar phenomenon was occurred but with higher pH and lower chlorine content in the condensed water, suggesting the production of inorganic salt rather than hydrochloric acid. Laboratory scale experiment was also performed to confirm the dechlorination phenomena especially for PVC, and the result showed that the main parameter which affected the dechlorination phenomena was the amount of water in hydrothermal process rather than limestone addition. It is suggested that a combination ofhydrothermal process and alkali addition would produce a low-chlorine solid product from plastic waste, promoting its usage as alternative solid fuel.

Test of membrane bioreactor for waste water treatment of a petrochemical complex

Membrane bioreactor (MBR) used in water and waste water treatment is a developing technique for water pollution control and water reuse. This paper described a membrane bioreactor for treatment of waste water in a petrochemical complex. The experimental MBR was a lab scale one composed of an activated sludge bioreactor unit and an ultrafiltration membrane unit. The relationship of COD removal with MLSS and HRT in this MBR was studied. The effects of crossflow velocity, backwash interval and volume of flush liquid on the flux were discussed. The results showed that average removal of COD, oil, SS and turbidity in petrochemical waste water by the MBR was 91%, 86%, 92% and 99%, respectively. The average removal of NH 3 N and total phosphorous was 85% and 82% respectively. A coefficient of COD removal, k , was 0017—0080 L/(mg.d). The membrane flux maintained higher than 60 L/hm 2 bar for 34 days without chemical cleaning when the velocity of crossflow was 35—39 m/s and the backwash interval was 30 minutes and backwash duration at 20 seconds. The results indicated that it is feasible for MBR technology to be used in petrochemical waste water treatment. The treated water could be considered as a source of to make up water for industrial cooling system or to be reused for other purposes.

Volumetric lattice Boltzmann method for pore-scale mass diffusionadvection process in geopolymer porous structures

Porous materials present significant advantages for absorbing radioactive isotopes in nuclear waste streams.To improve absorption efficiency in nuclear waste treatment,a thorough understanding of the diffusion-advection process within porous structures is essential for material design.In this study,we present advancements in the volumetric lattice Boltzmann method(VLBM)for modeling and simulating pore-scale diffusion-advection of radioactive isotopes within geopolymer porous structures.These structures are created using the phase field method(PFM)to precisely control pore architectures.In our VLBM approach,we introduce a concentration field of an isotope seamlessly coupled with the velocity field and solve it by the time evolution of its particle population function.To address the computational intensity inherent in the coupled lattice Boltzmann equations for velocity and concentration fields,we implement graphics processing unit(GPU)parallelization.Validation of the developed model involves examining the flow and diffusion fields in porous structures.Remarkably,good agreement is observed for both the velocity field from VLBM and multiphysics object-oriented simulation environment(MOOSE),and the concentration field from VLBM and the finite difference method(FDM).Furthermore,we investigate the effects of background flow,species diffusivity,and porosity on the diffusion-advection behavior by varying the background flow velocity,diffusion coefficient,and pore volume fraction,respectively.Notably,all three parameters exert an influence on the diffusion-advection process.Increased background flow and diffusivity markedly accelerate the process due to increased advection intensity and enhanced diffusion capability,respectively.Conversely,increasing the porosity has a less significant effect,causing a slight slowdown of the diffusion-advection process due to the expanded pore volume.This comprehensive parametric study provides valuable insights into the kinetics of isotope uptake in porous structures,facilitating the development of porous materials for nuclear waste treatment applications.

Development and commercial application of Baosteel sintering flue gas recirculating process

Because of the low temperature, large waste gas volume, high pollutant content, and complicated compositions, waste heat recovery and emission gas treatment of sintering flue gas have always presented a challenge in the steel industry, and this issue has attracted widespread attention both locally and abroad. Recently, based on the first domestic pilot plant and demonstration project, Baosteel has performed a series of innovative research and development investigations on its sintering flue gas recirculating （SFGR） process,in which the system design and optimization, dioxin-related contaminant source suppression, ore matching structure optimization, wear- resistant design of cycling fans and pipelines, high-efficiency dust removal equipment, system control and stable operation strategy, flue gas mixing and switching control, circular hood sealing, oxygen content conditioning, recirculation sintering system process control, and model development have been studied, and a complete set of equipment and technology for the SFGR process has been initially developed. The investigation results suggest that the SFGR process can not only significantly reduce exhaust gas volume and pollutant emissions but also recover low-temperature waste heat and reduce the energy consumption of sintering; therefore, the overall technologies possess great value in energy savings ,pollution emission reduction, and sintering ore quality/yield improvement.

Empirical Investigation of Treatment of Sour Gas by Novel Technology: Energy Optimization

The sour gas sweetening is one of the main processes in gas industries. Gas sweetening is done through chemical processes. Therefore, it requires high cost and energy. The results show that increasing the operating temperature increases the mass transfer coefficient and increases the mass transfer rate. Theoretical and experimental data show that sulfur removal in 4.5 W magnetic field is desirable. The increase in sulfur removal percentage in the magnetic field of 4.5 W and 6.75 W is about 16.4% and 15.2%, respectively. According to the obtained results, the effect of temperature increase from 18.8°C to 23.4°C is more evident than the effect of temperature change from 23.4°C to 32.2°C. Because more thermal energy is needed to provide higher temperatures. Therefore, the temperature of 23.4°C is reported as the optimal temperature. The results of this research show that the percentage of sulfur removal is also high at this temperature.

Optimization of Hydrothermal Treatment Parameters to Produce Chlorine-Free Alternative Solid Fuel from Plastic-Contained Municipal Solid Waste

An experimental study of the treatment of plastic-contained Japanese MSW （municipal solid waste） employing 1 ton capacity hydrothermal reactor to produce chlorine-free solid fuel has been performed. The system applies medium-pressure saturated steam at about 2 MPa in a stirred reactor for certain holding period. It was shown that the products exhibited organic chlorine conversion into inorganic chlorine, which can then be water washed. To obtain an optimal operating condition, the temperature and holding period was integrated into one parameter called RS （reaction severity）. It was found that to convert 75% organic chlorine in the MSW, the optimum RS number correlates to an operating temperature of about 225℃ and holding period of 90 min, or 235 ℃ for 60 min. Since hydrothermal treatment is a batch process, a shorter holding period is preferable to increase the number of batches and indirectly increase its processing capacity.

Application of UASB Reactor in Leachate Treatment of Beijing Asuwei Waste Sanitary Landfill Site

The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in the debugging process,and the results showed that the VFA content in the anaerobic tank was controlled within 600 mg/L,which indicated that the water quality did not have the acidified phenomenon.The COD removal efficiency was 50%approximately and NH_3-N concentration showed as light decline when operation stability in anaerobic system.

An Overview of Mineral Processing in China

The latest progress in mineral processing in China is described. It is also pointed out that the existing technology can not meet the needs of economic development. The combined challenges of poor resources, economical benefits and environmental pollution issues require further research to upgrade the separation efficiency economically. The methods of mineral processing should play a more important part in waste treatment such as wastewater treatment, the remediation of contaminated soil and the recycling of wastes. Biomineral technology will be utilised in the near future.

Electrochemical CO_(2) mineralization for red mud treatment driven by hydrogen-cycled membrane electrolysis

CO_(2)mineralization as a promising CO_(2)mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO_(2).The red mud is a strong alkalinity waste residue produced from the aluminum industry by the Bayer process which has the potential for the industrial CO_(2)large scale treatment.However,limited by complex components of red mud and harsh operating conditions,it is challenging to directly mineralize CO_(2)using red mud to recover carbon and sodium resources and to produce mineralized products simultaneously with high economic value efficiently.Herein,we propose a novel electrochemical CO_(2)mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis,realizing mineralization of CO_(2)efficiently and recovery of carbon and sodium resources with economic value.The system utilizes H_(2)as the redox-active proton carrier to drive the cathode and anode to generate OH^(-) and H^(+) at low voltage,respectively.The H^(+) plays as a neutralizer for the alkalinity of red mud and the OH^(-) is used to mineralize CO_(2)into generate highpurity NaHCO_(3)product.We verify that the system can effectively recover carbon and sodium resources in red mud treatment process,which shows that the average electrolysis efficiency is 95.3%with highpurity(99.4%)NaHCO_(3)product obtained.The low electrolysis voltage of 0.453 V is achieved at10 mA·cm^(-2) in this system indicates a potential low energy consumption industrial process.Further,we successfully demonstrate that this process has the ability of direct efficient mineralization of flue gas CO_(2)(15%volume)without extra capturing,being a novel potential strategy for carbon neutralization.

Utilisation of waste heat from exhaust gases of drying process

Nowadays a lot of low-grade heat is wasted from the industry through the off- and flue-gasses with different compositions. These gases provide the sensitive heat with utilisation potential and latent heat with the components for condensation. In this paper, process integration methodology has been applied to the partly condensed streams. A hot composite curve that represents the gas mixture cooling according to equation of state for real gases was drawn to account the gas-liquid equilibrium. According to the pinch analysis methodology, the pinch point was specified and optimal minimal temperature difference was determined. The location of the point where gas and liquid phases can be split for better recuperation of heat energy within heat exchangers is estimated using the developed methodology. The industrial case study of tobacco drying process off-gasses is analysed for heat recovery. The mathematical model was developed by using MathCad software to minimise the total annualised cost using compact plate heat exchangers for waste heat utilisation. The obtained payback period for the required investments is less than six months. The presented method was validated by comparison with industrial test data.

Removal of odors and VOCs in municipal solid waste comprehensive treatment plants using a novel three-stage integrated biofilter:Performance and bioaerosol emissions

A novel three-stage integrated biofilter(TSIBF)composed of acidophilic bacteria reaction segment(ABRS),fungal reaction segment(FRS)and heterotrophic bacteria reaction segment(HBRS)was constructed for the treatment of odors and volatile organic compounds(VOCs)from municipal solid waste(MSW)comprehensive treatment plants.The performance,counts of predominant microorganisms,and bioaerosol emissions of a flill-scale TSIBF system were studied.High and stable removal efficiencies of hydrogen sulfide,ammonia and VOCs could be achieved with the TSIBF system,and the emissions of culturable heterotrophic bacteria,fungi and acidophilic sulfur bacteria were relatively low.The removal efficiencies of different odors and VOCs,emissions of culturable microorganisms,and types of predominant microorganisms were different in the ABRS,FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment.The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing.The rational segmentation,filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols,thus reducing the emissions of microorganisms from the bioreactor.

HEAVY METAL PARTITIONING IN A NUCLEAR WASTE TREATMENT PLANT

The fate of different trace elements and radio nuclides in the new ZWILAG nuclear waste treatment plant （Switzerland） has been modelled, in order to predict and check the transport behaviour of the volatile species and their distribution in the plant. Calculations show that for active waste from medicine, industry, research （MIR waste） only Zn and Cs have stable gaseous species at 1200℃. The investigations confirm the efficiency of the examined flue gas cleaning system.

Performance of two biofilters with neutral and low pH treating off-gases

Two different functional biofilters were carried out and compared for the treatment of off-gas containing multicomponent odors and volatile organic compounds (VOCs) in this study. The effects of pH values and the empty bed retention time (EBRT) on the performance of the bioreactors were studied; and the characteristics of microbial populations in the two biofilters were also determined. The experimental results indicated that the removal effciencies of hydrophilic compounds such as butyric acid and ammonia ...

Process Development and Design of Chlorine Dioxide Production Based on Hydrogen Peroxide

This paper presents a process development and design of chlorine dioxide production based on hydrogen peroxide. The process is characterized by cleaner production, high efficiency, and waste minimization. Optimization of process conditions, selection of equipment, and experiment of recycle of waste acid are carried out. The process design is realized in consideration of several aspects such as operation, material, equipment design and safety. An industrialized process flowsheet is developed according to experiment. A pilot testing is carried out to confirm the lab results. Process design of chlorine dioxide production based on hydrogen peroxide is realized.

Experimental study on SO_2 recovery using a sodium-zinc sorbent based flue gas desulfurization technology

A sodium–zinc sorbent based flue gas desulfurization technology(Na–Zn-FGD) was proposed based on the experiments and analyses of the thermal decomposition characteristics of Ca SO3 and Zn SO3·2.5H2 O, the waste products of calcium-based semi-dry and zinc-based flue gas desulfurization(Ca–SD-FGD and Zn–SD-FGD) technologies, respectively. It was found that Zn SO3·2.5H2 O first lost crystal H2 O at 100 °C and then decomposed into SO2 and solid Zn O at 260 °C in the air, while Ca SO3 is oxidized at 450 °C before it decomposed in the air. The experimental results confirm that Zn–SD-FGD technology is good for SO2 removal and recycling, but with problem in clogging and high operational cost. The proposed Na–Zn-FGD is clogging proof, and more cost-effective. In the new process, Na2CO3 is used to generate Na2SO3 for SO2absorption, and the intermediate product Na HSO3 reacts with Zn O powders, producing Zn SO3·2.5H2 O precipitate and Na2SO3 solution. The Na2SO3 solution is clogging proof, which is re-used for SO2 absorption. By thermal decomposition of Zn SO3·2.5H2 O, Zn O is re-generated and SO2 with high purity is co-produced as well. The cycle consumes some amount of raw material Na2CO3 and a small amount of Zn O only. The newly proposed FGD technology could be a substitute of the traditional semi-dry FGD technologies.

锆基非晶合金电解质等离子体抛光工艺及废液处理

电解质等离子体抛光技术在非晶合金结构件的应用仍处于探索阶段,而且会产生含较高浓度的重金属和氟离子废液。为了提高锆基非晶合金结构件的表面质量以满足其使役性能,研究抛光时间、工作电压、硫酸铵浓度、初始温度、工件入水深度、阳极挂具材料等电解质等离子体抛光工艺参数对锆基非晶合金表面粗糙度、晶化情况的影响,并利用正交试验进行参数组合优化,对比不同参数对于表面粗糙度的影响显著程度。最后针对抛光后废液污染的问题,探究并配套合适的废液处理方案。结果表明:影响抛光后材料表面质量因素的显著程度为抛光时间>工作电压>初始温度>硫酸铵浓度,最优抛光工艺参数组合为抛光时间8 min,工作电压220 V,初始温度88℃,硫酸铵浓度为5%,此时表面粗糙度为0.103μm。经化学混凝沉淀法和离子交换树脂法组合工艺处理后,出水废液中的重金属和氟离子浓度均能达国家电镀污染物排放标准。研究成果可为电解质等离子体抛光在锆基非晶合金的实际生产提供工艺指导,有助于推广锆基非晶合金结构件的产业化应用,促进锆基非晶合金的大规模工业生产。

尾菜批式中温发酵和高温发酵过程对比试验研究

尾菜的快速无害化处理已成为高原夏菜产业发展的“瓶颈”。针对目前尾菜规模化处理厂普遍存在厌氧发酵过程不稳定,而国内外缺少尾菜恒温发酵过程研究的现状,在0.56 m^(3)的恒温发酵罐中开展了尾菜批式中温发酵和高温发酵过程的对比试验,对比了两个过程中沼气产气量、氨氮量、pH值和溶解性总固体的变化过程,并用修正的Gompertz方程分析了恒温厌氧发酵产甲烷过程,研究结果表明:在接种量30%、总固体含量(Total Solid,TS)2.2%的30天批式发酵过程中,中温发酵过程和高温发酵过程均可稳定进行,与修正的Gompertz方程拟合结果吻合度R^(2)均大于0.99。高温组累积产气量、产甲烷量分别为3939 L、2034.2 L,比中温组分别高出11.3%和15.5%,同时高温组甲烷体积分数达到50%的时间较中温组提前了3 d;中高温两试验组对应的最低pH值分别为6.66和6.52,后期均逐渐升高并稳定在7.30左右;两试验组氨氮浓度呈前期快速上升后持续上下浮动趋势,整体高温组大于中温组。试验研究为使用恒温厌氧发酵稳定快速无害化、规模化处理尾菜提供了借鉴和参考。

尾菜集约化处理系统的运行状况及优化分析

为探究大量未经科学化处理的尾菜污染环境及资源浪费问题的有效解决方法,以甘肃省兰州市某尾菜处理和循环利用系统工程为案例,对现行尾菜集约化处理模式下系统的运行现状进行分析。结果表明:该系统在2022年运行期间共处理尾菜48351.72 t,折合尾菜产气能力为10.85 m^(3)/t,达标废水排放量共计48646 m^(3),产沼渣共计3901.5 t,处理成本达到86.78元/t;系统在运行过程中对尾菜的可回收资源利用不充分,未实现完全无害化,整体存在效率低、能耗高和运行成本高等问题。针对现行系统存在的问题分析其原因并提出系统运行的优化方案,为尾菜集约化处理模式的工艺优化提供一定依据,对尾菜资源化利用的持续健康发展有重要意义。

预处理-厌氧处理-MAP-生物脱氮组合工艺高效处理餐厨垃圾渗滤液工程

上海某区产生的餐厨垃圾渗滤液油分、固体悬浮物含量大,同时有机物、氨氮和总磷浓度高,属于难处理有机废水。本工程采用预处理-厌氧反应器-磷酸铵镁(magnesium ammonium phosphate,MAP)反应器-生物脱氮组合工艺处理餐厨垃圾渗滤液,处理能力达到100 m^(3)/d。预处理采用三相分离机分离浮渣油脂等物质。厌氧处理阶段通过两级厌氧处理工艺强化废水有机质降解去除。组合工艺系统对水量水质变化有较强抗冲击负荷能力。工程运行表明,组合处理工艺出水平均COD_(Cr)质量浓度为245 mg/L,氨氮质量浓度为6 mg/L,总氮质量浓度为40 mg/L,总磷质量浓度为4 mg/L,出水水质达到了上海市《污水综合排放标准》(DB 31/199—2018)的三级纳管标准。工程吨水处理成本为134.57元,进一步表明预处理-厌氧反应器-MAP-生物脱氮组合工艺是处理餐厨垃圾渗滤液的有效方法。