Effluent Of Secondary Sedimentation Tank Research Articles

Visible light-driven Cl-g-C3N4 activated peroxydisulfate process for TMP efficient degradation in a wide pH range

A narrow pH-applicability range can impact the actual treatment efficiency of AOPs, so the application of a wide pH range in AOP technology has garnered significant attention. In this study, the Cl-doped g-C3N4 as a visible light catalyst to activate the peroxydisulfate (PDS) process, named Vis/Cl-g-C3N4/PDS, was developed for trimethoprim (TMP) degradation in a wide pH range of 3–11. Results show that the Vis/Cl-g-C3N4/PDS process exhibited degradation efficiencies for TMP that were 1.39 times and 7.74 times higher than those of the Vis/Cl-g-C3N4 process and the Vis/g-C3N4 process, respectively. The Vis/Cl-g-C3N4/PDS process perfectly achieved degradation rates of over 98 % for TMP within a wide pH range of 3–11. It concluded that the high efficiency of the Vis/Cl-g-C3N4/PDS process in degrading TMP over a wide pH range was caused by the two co-existing reactive oxygen species (ROS) generation mechanism pathways: the photocatalytic activation of PDS and the light-assisted hydrolysis of PDS. Moreover, after 3 h of illumination in the Vis/Cl-g-C3N4/PDS process, a degradation range of 85.7 %–97.8 % was demonstrated in various real water matrices including of tap water, secondary sedimentation tank effluent, surface water, and aquaculture water. This study provided practical significance for the practical application of AOPs in water environmental pollution control.

Combined oxidation and in-situ coagulation in iron-activated sulfite process for tribromophenol removal in actual water matrix

In this study, Fe(III)/sulfite (S(IV)) system was used to treat two actual water samples including a lake water sample and a secondary sedimentation tank effluent sample containing tribromophenol (TBP) with...

Returnable MoS2@carbon nitride nanotube composite hollow spheres drive photo-self-Fenton-PMS system for synergistic catalytic and photocatalytic tetracycline degradation

In this work, we synthesized hollow sphere composites of MoS2@carbon nitride nanotube (MoS2@TCN-S) for in-situ formation of H2O2 under visible light. The photo-self-Fenton system was further coupled with peroxymonosulfate (P-SF-PMS) for promoted reactive oxygen species generation and tetracycline degradation, so that the P-SF-PMS(MoS2@TCN-S) system can remove 94.3 % TC within 120 min, and the removal efficiencies after 15 cycles decrease by less than 5 %. The P-SF-PMS(MoS2@TCN-S) system also shows excellent degradation performance for actual wastewater, with COD removal rates of domestic sewage and secondary sedimentation tank effluent reaching 64.6 % and 58.7 % within 120 min. Quenching experiment and ESR results reveal the synergy of PMS and P-SF system, which was the key to improving the degradability and pH (3–9) adaptability of the P-SF-PMS system. Under alkaline conditions, PMS and H2O2 generated on MoS2@TCN-S activate each other and form 1O2 and OH, which solves the problem of poor degradation of P-SF system under alkaline conditions. Under acidic and neutral conditions, O2– becomes the main ROS, the activation of PMS by O2– and the synergistic effect of PMS and H2O2 make the P-SF-PMS system get rid of the dependence on H+. In addition, direct Z-scheme heterojunction enables MoS2@TCN-S to exhibit faster electron transfer ability, faster H2O2 generation ability, stronger adsorption capacity for PMS, and lower activation barrier for *HSO5, which also enhances the synergistic effect between PMS and P-SF system. In this study, a new type of multi-functional water purification material is proposed, and the synergism of PMS and P-SF system is revealed.

Phosphorus removal by iron–carbon microelectrolysis: A new way to achieve phosphorus recovery

Abstract Iron–carbon microelectrolysis was employed to remove phosphorus in this study. The efficiency, mechanism, influence factors, and feasibility of actual wastewater were investigated. The results showed that iron–carbon microelectrolysis had an excellent phosphorus removal ability. When the initial concentration of PO 4 3 − {\text{PO}}_{4}^{3-} –P was 19.44 mg·L−1, after 120 min reaction time, the remaining PO 4 3 − {\text{PO}}_{4}^{3-} –P in wastewater was 4.65 mg·L−1, and the removal rate was 76.05%. The precipitate formed in the reaction was mainly ferric phosphate (FePO4), which had a high recovery value. There was a linear correlation between initial phosphorus concentrations and phosphorus removal velocity. As to actual wastewater, 88.37 ± 0.44%, 89.78 ± 1.88%, and 94.23 ± 0.16% phosphorus removal rates were achieved in the influent of municipal wastewater treatment plant, effluent of secondary sedimentation tank, and actual high salinity wastewater, respectively, after 120 min reaction time. This study provides a new method for phosphorus removal and recovery from wastewater.

Selection and Evaluation of Model Pollutants for Performance Assessment of Advanced Treatment of Industrial Park Wastewater by Ozonation

Ozonation has gradually become a routine process for advanced wastewater treatment. During the technology innovation on the advanced treatment of wastewater by ozonation, researchers have to assess the performance of abundant new technologies, new reactors, and new materials. However, they are usually puzzled by the rational selection of model pollutants to assess the capability of such new technologies to eliminate the chemical oxygen demand (COD) and total organic carbon (TOC) of practical wastewater. It is unclear how well the various model pollutants reported in the literature could represent the COD/TOC removal of actual wastewater. The rational selection and evaluation of model pollutants for advanced treatment of industrial wastewater is of great significance in establishing the technological standard system for advanced treatment of wastewater via ozonation. Herein, the aqueous solutions (including unbuffered solutions and bicarbonate-buffered solutions) of 19 model pollutants and four practical secondary effluents from industrial parks were investigated through ozonation under identical conditions. The similarity in COD/TOC removal of the above wastewater/solutions were evaluated using mainly clustering analysis. The results showed that the dissimilarity among the model pollutants was greater than that among the actual wastewaters, thus enabling the rational selection of several model pollutants to assess the performance of advanced treatment of wastewater using ozonation by different technologies. The errors of predicting the COD removal of secondary sedimentation tank effluent by ozonation in 60 min using the unbuffered aqueous solutions of ketoprofen (KTP), dichlorophenoxyacetic acid (2,4-D), and sulfamethazine (SMT) were less than 9%, and those using the bicarbonate-buffered solutions of phenacetin (PNT), SMT, and sucralose were less than 5%. The evolution of pH by using the bicarbonate-buffered solutions was more similar to that in practical wastewater than by using unbuffered aqueous solutions. In the similarity evaluation of COD/TOC removal between the bicarbonate-buffered solutions and the practical wastewaters, the results were almost the same whether considering different input ozone concentration conditions. Therefore, the protocol proposed in this study based on similarity evaluation to assess the performance treating actual wastewater could be extended to different ozone concentration conditions with certain universality.

Significance of hydrodynamic cavitation to enhance reuse of secondary sedimentation tank effluent: a geometrical assessment

ABSTRACT Adequate wastewater management is an environmental concern because of the lack of freshwater resources, which brings about the quick augmentation of technologies for complete quantitative and qualitative wastewater recovery. In the cluster of the advanced oxidation process, hydrodynamic cavitation developed as a promising technology to treat wastewater, in the last couple of decades, due to its low-cost energy efficiency without aided and residual chemicals. In the present study, two pilot-scale experimental setups (I and II) of hydrodynamic cavitation reactor have been used to treat the secondary sedimentation tank (SST) effluent of natural six sewage treatment plant (STP) of Surat city for irrigational reuse, using an orifice as a cavitating device. At inception, the inlet pressure has been optimized, which follows the first-order kinetic rate constant. The pump power with respect to the diameter of the main pipeline has differentiated by keeping the constant dimension of the cavitating device to compare the geometrical effect and was analyzed using the number of rotations concerning recirculation time to degrade the chemical oxygen demand (COD). It is found that the maximum COD, total suspended solids (TSS), and most probable number (MPN) were degraded to 79.8%, 63.8%, and 99.5%, respectively, by setup II; also, descent within the permissible limit proclaimed by CPHEEO India to irrigate the non-edible crops.

Application of Effective Orifice Jet Length for Treating SST Effluent of STP by Hydrodynamic Cavitation

Advanced oxidation process in general and hydrodynamic cavitation, in particular, has emerged as a promising technology for the treatment of wastewater in the last few years as the process is energy-efficient and cost-effective. In this process, cavities are generated due to local pressure drops caused by constrictions. This work aimed to investigate the potential of hydrodynamic cavitation as a tertiary treatment to the secondary sedimentation tank effluent of a sewage treatment plant, with two laboratory-scale experimental setups having an orifice plate of a 1 mm diameter hole. The process dependency was estimated by optimizing inlet pressure (0.8 bar for setup I and 5 bar for setup II). Moreover, effective orifice jet length was varied to investigate the impact of fluid buoyancy force on expansion and collapse of a cavity on the chemical oxygen demand removal and disinfection. At L2 length (two-thirds of the original length), both setups can degrade the organic and inorganic pollutants to the maximum extent. With the optimum condition in setup II, maximum COD, TSS, and fecal coliform degradation were 80.47%, 62.83%, and 52.27%, respectively, compared to setup I.

Biological treatment of refractory pollutants in industrial wastewaters under aerobic or anaerobic condition: Batch tests and associated microbial community analysis

In this study, aerobic or anaerobic biological treatment of streams collected from different units of industrial wastewater treatment plant (WWTP) was studied in a series of batch tests. Under aerobic condition, the removal efficiencies of COD, NH4+-N and TP were 57.7%, 83.8% and 100% for influent of WWTP (IN), 64.4%, 61.3% and 100% for effluent of secondary sedimentation tank (EN-SST), and 2.3%, 64.3% and 10.6% for effluent of advanced oxidation tank (EN-AOT). Meanwhile, the removal efficiencies of COD, NH4+-N, TOC were above 30% under anaerobic conditions. The GC–MS analysis showed a presence of 59 kinds of chemicals in IN, 28 in EN-SST, and 8 in EN-AOT. The main organic compounds were long-chain alkanes and derivatives. After aerobic/anaerobic biological treatment, the abundance of Proteobacteria, Bacteroidota, Nitrospirota was 40.4–56.1% (IN), 5.3–17.5% (EN-SST), and 4.6–13.4% (EN-AOT), respectively. This work contributed to deeply understanding the biotransformation mechanisms of refractory pollutants in industrial wastewaters.

Development of a Polyaluminum Ferric Titanium Chloride for Phosphorous Removal in Water

Phosphorus removal is a promising means to effectively prevent and control the eutrophication of natural waters. Coagulation can achieve phosphorus removal with high efficiency, and therefore the preparation of coagulants has recently garnered increasing attention. Ferric chloride, aluminum chloride, and titanium tetrachloride were used to prepare polyaluminium ferric titanium chloride (i.e., PCAFT) by changing the molar ratio of trivalent iron, trivalent aluminum, and tetravalent titanium and adjusting the alkalization degree. The resulting compounds were characterized via X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to clarify their phosphorus removal mechanisms. Single-factor and orthogonal tests were conducted to determine the optimum conditions for phosphorus removal, after which the phosphorus-removing properties of the proposed material were assessed in actual wastewater. The optimum conditions for phosphorus removal were the following: coagulant dosage of 40 mg, wastewater pH of 9, and phosphorus wastewater concentration of 2 mg · L−1. Our proposed method could reduce the total phosphorus concentration of the secondary sedimentation tank effluent to below the detection limit. Moreover, the characterization results indicated that the synthesized PCAFT was a complex hydroxyl polymer of aluminum, iron, and titanium bridged by a hydroxyl group with good crystallinity and a cluster structure on its crystal surface, which enhanced the coagulation and phosphorus removal properties of the material.

Fouling mechanism of PVDF ultrafiltration membrane for secondary effluent treatment from paper mills

Papermaking industry discharges a huge amount of effluent and recycling of processed water with membrane technology has become predominate treatment protocol. In this study, poly(vinylidene fluoride) (PVDF) ultrafiltration membrane was employed to treat the effluent of secondary sedimentation tank from a paper mill. The results of 600 -hs continuous running showed that the PVDF membrane was seriously fouled with increased surface roughness during the filtrating process. Characterization of the fouled PVDF membrane revealed that pore blockage and cake deposition were the main fouling mechanism. The foulants in the pores were mainly oxygen-contained organics, and the foulants on the surface were mainly metal complexes and large particle. Wastewater analysis indicated the co-existence of PVA (1.0 mg/L) and Ca2+ (16.7 mg/L) in the secondary effluent. Pores blocking mechanism was caused by strong adheresion of PVA-217 and cake deposition mechanism was induced with macromolecular complexes of calcium ions bonding to PVA-217. The results obtained in this study demonstrated the fouling mechanism in the secondary effluent treatment. The understanding could help to find a feasible chemical method to clean the fouled polymeric membrane with washing agents as NaClO, NaOH and HCl in steps.

Flocculation Efficiency and Mechanism of Carbamazepine by Microbial Flocculant Extracted from Klebsiella pneumoniae J1.

The microbial flocculant (MFX) extracted from Klebsiella pneumoniae J1 was used to remove carbamazepine in prepared wastewater and domestic sewage. The influence factors and flocculation mechanism were studied. The optimal carbamazepine removal conditions for MFX were pH of 7-8, 7 mL of flocculant, 0.1 mL of coagulant, and 35°C, and the removal rate reached 81.75%. MFX was efficient in the removal of carbamazepine in both domestic sewage (75.03%) and secondary sedimentation tank effluent (69.76%). The pseudo-first-order kinetic equation fitted the adsorption process better than the pseudo-second-order kinetic equation, which suggested that the adsorption was not pure chemical adsorption. The analysis of floc size suggested that the repulsive force between carbamazepine and MFX was weakened under alkalescent conditions, which can help the growth and coherence of flocs and increase the carbamazepine removal efficiency. Enough dosage of MFX can generate larger flocs, but excessive dosage of MFX will decrease the carbamazepine removal rate because of increase in electrostatic repulsion. The analysis of 3D-EEM and FTIR suggested that hydroxyl, amino, and carboxyl in MFX played an important role in the removal of carbamazepine. As an eco-friendly and highly efficient microbial flocculant, MFX has potential for practical applications in carbamazepine removal.

Simultaneous nutrition removal and high-efficiency biomass and lipid accumulation by microalgae using anaerobic digested effluent from cattle manure combined with municipal wastewater

BackgroundMicroalgae as a viable biodiesel feedstock show great potential to approach the challenges of energy shortage and environment pollution, but their economic feasibility was seriously hampered by high production cost. Thus, it is in urgent need to reduce the cost of cultivation and improve the biomass and lipid production of microalgae. In this work, anaerobic digestion effluent from cattle manure combined with municipal wastewater was used as a cost-effective medium for cultivating microalgae and expected to obtain high biomass. The pretreatment of anaerobic digested effluent containing dilution rate, sterilization and nutrient optimization was investigated. Then, initial pH and light intensity for algal growth, lipid production and wastewater purification were optimized in this study.ResultsScenedesmus sp. could grow rapidly in 10% anaerobic digestion effluent from cattle manure combined with secondary sedimentation tank effluent without sterilization. Optimum nutrient additives for higher biomass were as follows: glucose 10 g/L, NaNO3 0.3 g/L, K2HPO4·3H2O 0.01 g/L, MgSO4·7H2O 0.075 g/L and trace element A5 solution 1 mL/L. Biomass of 4.65 g/L and lipid productivity of 81.90 mg/L/day were achieved during 7-day cultivation accompanying over 90% of COD, NO3−-N, NH4+-N, and 79–88% of PO43−-P removal with optimized initial pH of 7.0 and light intensity of 5000 l×. The FAME profile in ADEC growth medium consisted in saturated (39.48%) and monounsaturated (60.52%) fatty acids with the 16- to 18-chain-length fatty acids constituting over 98% of total FAME.ConclusionsThis study proves the potential of anaerobic digested effluent combined with municipal wastewater for microalgae culture, and provides an effective avenue for simultaneous microalgal lipid production and treatment of two kinds of wastewater.

Performance of simultaneous wastewater reuse and seawater desalination by PAO-LPRO process

Abstract Water shortage worldwide is calling for efficient technologies for water purification and reuse. A new process combined pressure assisted osmosis (PAO) and low pressure reverse osmosis (LPRO) was instructed to achieve simultaneous wastewater reuse and seawater desalination. The operating conditions of PAO and LPRO were optimized. Excitation-emission matrix (EEM) spectroscopy and gel permeation chromatography (GPC) were used to investigate the changes of molecular weight distribution (MWD) of organic matters in the hybrid process. Results indicated that water flux was proportional to the pump pressure, and reverse salt flux decreased with the pressure decreasing in single PAO process. Severe permeate flux and salt rejection declination were observed when high concentration NaCl was used as influent in single LPRO process. In hybrid PAO-LPRO process, permeate flux significantly increased compared with single LPRO process and product water had high quality according to the results of EEM spectroscopy and MWD analysis. Salt rejection and removal efficiency of total organic carbon were 97.8% and 98%, respectively. Membrane fouling was moderate and could be removed by simple physical cleaning when secondary sedimentation tank effluent (SSTE) from wastewater treatment plant was used as feed solution and seawater from Hangzhou bay as draw solution.

Effect of different carriers and operating parameters on degradation of flax wastewater by fluidized-bed Fenton process.

This investigation evaluates the effectiveness of a fluidized-bed Fenton process in treating flax wastewater. Flax wastewater was taken from a paper-making factory in a secondary sedimentation tank effluent of a paper-making factory in Hebei. The performance of three carriers (SiO2, Al2O3, Fe2O3) used in the reactor was compared, and the effects of different operational conditions, and Fenton reagent concentrations were studied. Experimental results indicated that SiO2 was the most appropriate carrier in the system. The dose of Fe2+ and H2O2 was a significant operating factor in the degradation progress. The bed expansion was considered to be another factor influencing the treatment effect. Under the appropriate conditions (300 mg/L Fe2+, 600 mg/L H2O2, and 74.07 g/L SiO2 as the carrier, at pH=3, 50% bed expansion), the highest removal rate of total organic carbon (TOC) and color was 89% and 94%, respectively. The article also discussed the process of the colority removal of flax wastewater and the kinetics of TOC removal.

Productive Experiment on Short-Time Aeration Treatment of Municipal Sewage

COD and BOD of the inflow of aeration basin and the effluent of secondary sedimentation tank were detected through orthogonal test.The test use removal rate of COD and BOD as evaluation index, B/C as analysis index. The result of the test indicated that the best working condition can be achieved when there are 3 water pumps for inflow, the concentration of activated sludge stands at 1600mg/L, and HRT in the aeration basin and secondary sedimentation tank stand at 1.86 hours and 2.87 hours respectively. The test demonstrated that short-time aeration can reduce the energy consumption and, therefore, the cost effectively, while insure the effluent reach the outlet qualitative standard. This is suitable for sewage treatment plants in south China since the concentration of their inflow is low.

The fate of dissolved organic carbon (DOC) in the wastewater treatment process and its importance in the removal of wastewater contaminants

Dissolved organic carbon (DOC) constitutes a parameter of organic pollution for waters and wastewaters, which is not so often studied, and it is not yet regulated by directives. The term 'DOC' is used for the fraction of organics that pass through a 0.45 microm pores' size membrane. The type of wastewater plays an important role in the quality of DOC and it has been shown that DOC may contain aquatic humic substances, hydrophobic bases, hydrophobic neutrals, hydrophilic acids, hydrophilic bases and hydrophilic neutrals. The quality of the DOC is expected to affect its fate in a wastewater treatment plant (WWTP), since a considerable fraction of DOC is not biodegradable, and it may be released in the aquatic environment together with the treated effluent. In the present study, the occurrence of DOC during the wastewater treatment process is investigated and its removal rates during primary, secondary and overall treatment are being estimated. Furthermore, a correlation is being attempted between DOC and the concentrations of selected Persistent Organic Pollutants (POPs) and Heavy Metals (HMs) in the dissolved phase of wastewaters, to examine whether there are common sources for these pollution parameters in WWTPs. Also, DOC is being correlated with the partition coefficients of the above-mentioned pollutants in wastewater, in order to examine the effect of 'solubility enhancement' in WWTPs and to evaluate the result of this phenomenon in the efficiency of a WWTP to remove organic pollutants. For the purposes of this study, 24-h composite wastewater samples were collected from the influent (raw wastewater, RW), the effluent of primary sedimentation tank (primary sedimentation effluent, PSE) and the effluent of secondary sedimentation tank (secondary sedimentation effluent, SSE). Samples were analyzed for the presence of 26 POPs (7 PCBs and 19 organochlorine pesticides), 8 HMs and DOC. Mean concentrations of DOC in RW and PSE were at similar levels (approximately 70 mg l(-1)), suggesting that primary treatment has a minor effect on the DOC content of wastewater. DOC concentrations in SSE were significantly lower (approximately 19 mg l(-1)) as a result of the degradation of organic compounds in the biological reactor. Calculated removals of DOC were 0.8% in the primary treatment, 63% in the secondary treatment, and 69% in the overall treatment, exhibiting large differences from other organic pollution parameters, such as BOD and COD. The overall DOC removal was found to be independent from the DOC concentration in raw wastewater. Poor correlation was also observed between the DOC content and the concentrations of wastewater contaminants, such as persistent organic pollutants (POPs) and heavy metals (HMs), probably suggesting that their occurrence in WWTPs is due to different sources. A good negative linear relationship was revealed between DOC concentrations and the logarithms of the distribution coefficients (Kd) of various POPs and HMs between the solid and the liquid phases of wastewater. This relationship suggests that DOC facilitates hydrophobic pollutants to remain in the dissolved phase thus causing lower removal percentages during the treatment process. DOC was measured at three stages of a municipal WWTP that receives mainly domestic wastewater and urban runoff. DOC concentrations in untreated and primarily treated wastewater were almost equal, and only after the secondary sedimentation there was a decrease. Concentrations and removal rates of DOC were in the same levels as in other WWTPs that receive municipal wastewater. The origin of DOC was found to be different to the one of POPs and of HMs, as no correlation was observed between the concentrations of DOC and the concentrations of these pollutants. On the contrary, DOC was found to have significant negative correlation with the Kd of all pollutants examined, suggesting that it plays an important role in the partitioning of those pollutants between the dissolved and the sorbed phase of wastewaters. This effect of DOC on partitioning can affect the ability of WWTPs to remove toxic pollutants, and that way it facilitates the discharge of those chemicals in the aquatic ecosystems together with the treated effluent. RRECOMMENDATION:By the results of this work it is shown that the presence of DOC in wastewaters can significantly affect the partition of hazardous pollutants between the dissolved and the sorbed phase. It is therefore of importance that this parameter is controlled more in wastewaters, since it can cause a decrease in the efficiency of WWTPs to remove quantitatively persistent pollutants.