Model Of The Relationship Between Substances And Energy Consumption In Wastewater Treatment Processes

The activated sludge method has evolved over the past 100 years and a variety of biological treatment processes have been developed to date.As the most widely used process configuration,the front anaerobic(A/O,A/A/O,A/O/O,etc.)are widely used in the treatment of municipal sewage.However,for industrial wastewater with high toxicity,high total nitrogen concentration and high C/N ratio,many shortcomings are revealed,including sludge retention time(SRT)control,functional bacteria enrichment,reflux affecting denitrification and energy efficiency,which cannot achieve the goal of ultra-low total nitrogen discharge based on internal carbon sources.Therefore,new process theories and treatment process technologies must be developed by considering the solution properties of typical industrial wastewater.However,the variabilities of wastewater solution properties,biological treatment processes and discharge targets greatly increase the difficulty in process design and operation,and make it cannot be fully revealed through experiments alone.Mathematical models possess characteristics that derived from and surpass reality,making them an inevitable choice for exploring new process theories.The most influential mathematical models for wastewater treatment are the activated sludge models(ASMs)proposed by the International Water Association(IWA).However,ASMs are specific designed for municipal wastewater,both in terms of model structure and parameter values,and do not include inorganic nitrogen components(e.g.thiocyanide and cyanide)and toxicity inhibition effects.Hence,ASMs are not applicable to industrial wastewater simulation.This thesis firstly explores the relationship between process principles and wastewater treatment,using A/O/H/O as the process platform and selecting coking wastewater as the object of study(Chapter 3).The CW-ASM3 model was developed based on cyanide and thiocyanide components and cyanide inhibition kinetic parameters in coking wastewater,and then the treatment performance of different processes was explored by varying the hydraulic retention time(HRT)of the A/O/H/O process platform.It was found that:(1)the microbial activity of the A-reactor was inhibited by toxicity,and the degradation rate of COD was less than 5%,which had little role in the process;(2)the O1 reactor was able to achieve COD removal,detoxification,ammonification and even nitrification,which was an important guarantee for the subsequent denitrification process;(3)compared with other processes,the O/H/O process had obvious advantages for the treatment of highly toxic industrial wastewater;(4)under the model conditions,the O/H/O process can reduce 632.2 g COD and 45.2 g TN by per 1 k Wh electricity.O/H/O is a simpler process than A/O/H/O and there is a lack of analysis of the diversity of operating modes that place O reactor in front.To investigate the relationship between operational modes,water quality,and energy consumption,the one-step nitrification denitrification process in the CW-ASM3 model was divided into two separate steps:nitrification and denitrification(TCW-ASM3 model).And the different operation modes of the O/H/O process were simulated using the TCW-ASM3 model(Chapter 4).The results show that:(1)an increase in the affluent ratio R1 in the range of 0%～50%has almost no effect on the COD and energy consumption of the biological effluent,while every increase of 10%in the range of50%～100%can raise the effluent COD by 238.8 mg/L and reduces the energy consumption by0.27 k Wh/m~3;(2)within the range of 0%～100%,every increase of R1 by 10%increases the biological effluent TN by 13.4 mg/L;(3)the nitrification liquor reflux ratio R2 has no effect on COD;(4)R2 decreases TN by 7.46 mg/L for every 10%increase in the range of 0～220%and0.64 mg/L for every 10%increase in the range of 220%～1000%;(5)every 100%increase in R2 increases energy consumption by 0.12 k Wh/m~3;(6)The O/H/O process can be adjusted in different modes according to pollutant characteristics and effluent targets,and there is room for further optimization.The effect of operating mode on effluent concentration and energy consumption is influenced by the combined intervention of reaction kinetics and toxicity inhibition,i.e.the operating mode changes the wastewater solution properties of the receptor unit and determines the pollutant removal efficiency.Subsequently,the functional significance of A in the A/O/H/O process was further expanded,including Anaerobic,Adsorption,Air flotation/coagulation,Accelerated solvents extraction and Application of REDOX Technology(ART).The expanded process is named the A-O/H/O process and several design examples of the A-O/H/O process are provided(Chapter5).Finally,an economic benefit analysis of the A-O/H/O process is provided using adsorption A as an example(Chapter 6).The case study uses powdered activated carbon(PAC)as the adsorbent to construct a combined technology of pre-and post-physicochemical treatment(CT2PC).The results show that the cost of the adsorbent can be compensated by the net benefit of energy recovery.Profitability can be achieved when the price of PAC is below 5562 CNY/t,the raw wastewater concentration is 4800-6000 mg/L and the adsorption capacity is greater than0.7 kg COD/kg PAC.This study demonstrates that the A-O/H/O process is a combination treatment technology with adjustable cost effectiveness that enables risk transfer and mass-energy conversion of pollutants.In summary,this paper presents the concept of the A-O/H/O process platform and analyses various cases of this platform(A/O/H/O,O/H/O,Adsorption-O/H/O),including water quality,energy consumption and economy.It reveals the process principle and operation patterns of the A-O/H/O process platform and broadens the diversity of process units and combinations for wastewater treatment.As a highly promising process platform,the design and operation of the A-O/H/O process should be based on the judgement of the wastewater solution properties,the knowledge of the reaction principles of wastewater treatment,and the comprehensive consideration of the pollutant component transformation and discharge limits.The combined process for the treatment of complex industrial wastewater,the optimization of the material flow,energy constraints and reaction objectives in a collection,it must be based on a hierarchical understanding of elemental-compound-solution properties and the assessment of discharge reduction benefits.