[Objective]With the further improvement of urbanization,the original designed influent pollutant concentration load of the wastewater treatment plant(WWTP)has increased.A WWTP in northwest China country is designed with a wastewater treatment capacity of 8 000 m3/d,ammonia nitrogen mass concentration of 32 mg/L,and total nitrogen(TN)mass concentration of 45 mg/L.The cyclic activated sludge system(CASS)process is adopted.The effluent quality follows the class A criteria of Discharge Standard of Water Pollutants for Municipal Wastewater Treatment Plants(GB 18918-2002).However,the actual influent quality of ammonia nitrogen and TN mass concentrations are 71-117 mg/L and 78-127 mg/L,respectively.And these concentrations are exceeding the design influent concentrations from 1.21 times to 2.65 times and from 0.73 times to 1.82 times,respectively.The effluent TN does not meet the discharge water quality requirement of 15 mg/L.[Methods]The small-scale hypoxic denitrification test is carried out.The further renovation idea is determined to enhance the dydraulic retention time of the activated sludge denitrification.Based on the problems of batch treatment of wastewater in CASS tank and the fact that the volume of the biological selection zone only accounts for 11.3％of the biological tank capacity,the renovation project will transform the regulating tank into an anoxic tank.On the basis of the effective capacity of 8 579 m3 in the CASS tank,an independent anoxic zone with the effective capacity of 3 091 m3 in the equalization is added.The nirtification reflux ratio has increased from the designed 24％to 114％.During the influent and aeration reaction stages of the CASS tank,the nitrification solution is refluxed to the equalization tank for anaerobic denitrification reaction,and then returned to the CASS tank with the influent to enhance the denitrification capacity of the biochemical tank.[Results]After 15 days of non-stop water supply during the renovation and commissioning,the TN in the effluent is stably up to standard.[Conclusion]This process renovation practice has solved the problem of insufficient nitrogen removal capacity in WWTP,especially in the county-level areas of the northwest region due to the excessive nitrogen load in the influent exceeding the designed water quality.Moreover,the renovation cost is extremely low.This project provides an economic,fast,and easy maintaining,and broad promotion value renovation path for small and medium sized WWTPs with the limited funds in the northwest region.
[Objective]As the global prevalence of microplastic pollution continues to rise,novel plastic varieties,exemplified by recycled plastics and bioplastics,are gaining significant attention owing to their inherent environmental friendliness and potential of ecological burdens reduction.While alleviating the environmental stress imposed by traditional plastics,novel plastics frequently assume a colloidal state subsequent to migration,adsorption,and agglomeration in aqueous environments,thereby potentially exerting an impact on the environment.In comparison with traditional microplastics,colloidal new microplastics(CNMPs)exhibit substantial disparities in environmental migration,detection methodologies,and treatment processes attributable to their colloidal stability and the unique properties of the novel plastic matrix.[Methods]This paper focuses on CNMPs in drinking water,the research progress of CNMPs in drinking water in recent years is summarized and elaborated from four aspects,namely,their overview,detection techniques,health risks and control strategies.[Results]During their long-term persistence in aquatic environments,CNMPs are prone to forming highly adsorptive and highly mobile particles through environmental processes such as aging and fragmentation,adsorption and aggregation.Traditional detection technologies exhibit limitations in sensitivity and accuracy for CNMPs detection,while emerging technologies,though more sensitive,have more stringent equipment requirements.This poses challenges to the accurate assessment of the distribution and exposure levels of CNMPs in the environment.CNMPs can exert potential threats to human health via the food chain.CNMPs are equipped with chemical additives and can adsorb toxic compounds,potentially disrupting the human endocrine system and leading to a range of health complications.In traditional drinking water treatment processes,oxidation and dissolved air flotation in the pretreatment stage can remove CNMPs to some extent,but their application in water treatment plants is not widely;conventional treatment processes,such as coagulation and sedimentation,have limited effectiveness in removing small-particle-sized CNMPs.Filtration processes are highly effective in removing CNMPs with particle sizes greater than 10 μm,but their effectiveness is limited for those smaller than 10 μm.Advanced treatment processes can attain removal efficiency of up to 90％for CNMPs,but they encounter challenges such as high costs and complex technology.[Conclusion]The research direction and control technology of CNMPs based on the current status of this paper are prospected,aiming to provide a key reference for water treatment technology to alleviate the new microplastic pollution problem.
[Objective]Standard for Drinking Water Quality(GB 5749-2022)lists two taste and odor substances,e.g.2-methylisoborneol(2-MIB)and geosmin(GSM)as mandatory indices of water quality enhancement.Algae outbreaks may cause a sharp increase of 2-MIB and GSM concentrations in raw water.However,conventional drinking water treatment processes(coagulation-sedimentation-filtration-disinfection)have limited effectiveness in removing 2-MIB and GSM.[Methods]Under existing raw water quality conditions of a certain reservoir in Ningbo City,the gas-liquid mass transfer efficiency of ozone titanium plate aeration and ozone ceramic membrane aeration was compared.Furthermore,the removal efficiency of typical taste and odor substances under different conditions was compared,and the effect of ozone dosage on the removal efficiency of taste and odor substances was investigated.Finally,the potential risks of disinfection byproduct generation during the chlorination process were evaluated for two different aeration method.[Results]Under the same aeration conditions,ceramic membrane aeration could dissolve ozone in water more quickly.The experimental results showed that the ozone concentration in the water reached 0.76 mg/L when the ceramic membrane was aerated for three minutes,while the concentration of ozone was only about 0.3 mg/L with the titanium plate.After five minutes,the ozone mass concentration of the ceramic membrane reached 0.80 mg/L,whereas the titanium plate required more time to reach the same concentration.At initial 2-MIB mass concentrations of 30 ng/L,60 ng/L,and 100 ng/L,both aeration methods showed some degree of removal efficiency.As the ozone dosage increased,the removal rates of 2-MIB and GSM increased in tandem,with the ceramic membrane aeration performing consistently better than the titanium plate aeration.Under the raw water conditions of Ningbo City reservoirs,ozone ceramic membrane aeration treatment did not cause excessive levels of by-products such as bromate,haloacetic acids,and haloacetic acids.[Conclusion]The ozone ceramic membrane aeration treatment can be used as an emergency treatment technology for waterworks in response to sudden contamination by taste and odor substances.
[Objective]Accurately predicting the water intake of water treatment plants(WTPs)is a crucial foundation for water resource planning and management.It aids in the rational allocation of water resources,production costs reduction,and simultaneously meeting urban water supply demands.This paper aims to construct an innovative hybrid model that facilitates precise prediction and scheduling optimization of WTP water intake,thereby enhancing the overall operational efficiency of WTPs and achieving the goal of energy conservation and emission reduction.[Methods]This paper innovatively combined the hydrodynamic model with the extreme gradient boosting(XGBoost)data model to construct a hybrid model that accurately predicted the inflow and generated a gradient optimized scheduling scheme.On the basis of considering the operational characteristics of the WTP,the hybrid model optimized the inflow to form a solution that met the actual scheduling needs and provided scientific support for scheduling personnel.Taking a WTP in Z City as an example,this paper introduced the operation overview and data sources of the WTP,elaborated on the model construction and optimization process,and verified the effectiveness and energy-saving analysis of the predicted results.[Results]The proposed hybrid model could accurately predict the inflow in the WTP and achieved relatively stable inflow scheduling in actual scheduling.The optimized scheduling scheme significantly reduced the power consumption of the pump group and lowered the overall operating costs of the WTP.Specifically,it was expected that the annual energy savings could reach 78 537 kW·h,saving approximately 68 327 yuan in electricity bills.[Conclusion]The hybrid model proposed in this paper successfully optimizes the inflow scheduling while ensuring the normal water supply of the WTPs,significantly reducing the energy consumption and operating costs of the WTPs.This paper not only provides new methods and ideas for optimizing the inflow scheduling of WTPs,but also provides important theoretical basis and technical support for energy conservation and emission reduction in WTPs in practical applications,with strong application value and promotion prospects.
[Objective]This paper aims to achieve nearly zero sludge discharge during the anoxic-oxic(AO)process operation using ultrasound-alkali pretreatment,and evaluate pollutants removal and effluent quality in a lab-scale system.[Methods]Waste sludge,which disintegrating by ultrasound-alkaline pretreatment(initial pH value was 12,ultrasonic energy density was 1.6 W/mL,reaction time was 70 min,pulse ratio was 2∶1),was returned to AO process for treating the actual wastewater.To minimize the effect of disintegrated sludge on effluent quality and improve total nitrogen(TN)removal efficiency,the sludge near-zero discharge AO process was optimized by increasing hydraulic retention time of aerobic tank from 12.0 h to 14.4 h and dosing external carbon sources[sodium acetate(NaAc),800 mg/L].[Results]Disintegrated sludge reusing increased chemical oxygen demand(COD)of effluent and was not conducive to meeting discharge standards,but didn't significantly impact the removal efficiency and concentration of ammonia nitrogen.The organics released from disintegrated sludge could be used as a carbon source,increasing the TN removal efficiency of the AO process from 49.7％to 62.0％and decreasing effluent TN concentration.After AO process optimization,the effluent quality met the discharge standard of the Integrated Discharge Standard of Water Pollutants(DB11/307-2013)class B.Meanwhile,the external carbon source dosage was saved 46.7％which was compared to the traditional AO process.In addition,this paper found that the concentration ratio of mixed liquid volatile suspended solids to mixed liquor suspended solids of near-zero sludge discharge AO process will decrease after operating stably for a period of time.[Conclusion]This paper confirms that the near-zero sludge discharge AO process based on the combined ultrasound-alkaline technology can achieve sludge carbon source utilization and reduced sludge discharge,offering insights for waste sludge near-zero discharge and resource recovery.
