Removal Rate Of Suspended Solids Research Articles

Application of multi index comprehensive evaluation method in the selection of wastewater treatment processes

The study comprehensively evaluates various wastewater treatment processes by using Grey Relational Analysis (GRA) and Analytic Hierarchy Process (AHP) to identify the optimal method for wastewater treatment. To conduct this evaluation, six key indicators were identified and used for assessment: five-day biochemical oxygen demand (BOD5) removal rate, chemical oxygen demand (COD) removal rate, ammonia nitrogen removal rate, total nitrogen removal rate, total phosphorus removal rate, and suspended solid removal rate. Initially, GRA was employed to calculate the grey relational degree of each treatment process based on the weights of the indicators, and the treatment processes were then ranked and analyzed according to these degrees. Subsequently, AHP was applied to construct a judgment matrix, determine the weights of each indicator, and ensure the matrix's rationality through consistency testing. The study reveals significant differences in the performance of various wastewater treatment processes among the indicators, with the Modified A2/O+AO process showing the highest comprehensive performance in the evaluation. The findings provide a scientific basis for improving efficiency, reducing pollution, and guiding policy and technological development.

Effects of reaction temperature and oxygen pressure on dissolved organic matter in hydrothermal reactions of municipal sludge: A comprehensive analysis

The impact of temperature and oxygen pressure on the basic performance of hydrothermal reactions and dissolved organic matter (DOM) was investigated. The results showed that total chemical oxygen demand and volatile suspended solids removal rate achieved a maximum of 72 % and 99 %, respectively, at 260 °C and 0.9 MPa oxygen pressure. Oxygen demonstrated a significant role in enhancing sludge particle dissolution. The interaction with temperature resulted in a complex trend for dissolved organic carbon (DOC) and specific ultraviolet absorbance at 254 nm. Acetic acid and formic acid were identified as the prominent volatile fatty acids, with formic acid prevalent at lower temperatures, while acetic acid accumulated with increasing temperature and oxygen pressure. Three-dimensional excitation emission matrix and Fourier transform ion cyclotron resonance mass spectrometry was also employed to analyse DOM as over half of the DOC remained unknown. Parallel factor analysis indicated that three components with 8 peaks in total might represent a universal feature for fluorescent DOM in hydrothermal reaction solution. The deciphered data from FTICR-MS indicated that lipids and lignins as well as CHOS and CHON molecules were the main components of DOM. Meanwhile, condensed hydrocarbons were formed at high temperatures in wet oxidation runs. Moreover, identification of C19H32O3S, C18H30O3S and C18H26N2O3 as crucial intermediates further enriched the understanding of hydrothermal reactions in municipal sludge.

Effects of different flocculants and environment on the flocculation effect of potato starch-processing wastewater

ABSTRACT Potato starch-processing wastewater belongs to high-concentration organic wastewater, as direct discharge is more polluting to the environment. Flocculation treatment, as the initial process of wastewater purification, can remove large debris in wastewater, reduce energy consumption for subsequent treatment and reduce production costs. In this study, the effects of traditional flocculants and biological flocculants on the treatment of potato starch-processing wastewater under different pH, dosage, stirring rate and settling time were studied. It was found that traditional flocculants and biological flocculants have their own advantages in the purification ability of organic matter, and the removal rates of suspended solids (SS) and total phosphorus (TP) of traditional flocculants are better than biological flocculants for sweet potato starch-processing wastewater, but the flocculation time and settling time are long. Biological flocculants are environmentally friendly, safe and non-polluting, and do not produce secondary pollution when the flocculation treatment of wastewater is conducive to the secondary reuse of wastewater and flocculation sediment resource treatment. According to the flocculation effect and cost, chitosan is the best flocculant for treating sweet potato starch-processing wastewater.

Seasonal tourism's impact on wastewater composition: Evaluating the potential of alternating activated adsorption in primary treatment

Primary treatment processes have gained attention in recent research and development due to their potential for redirecting carbon towards anaerobic digestion, which can subsequently be used for the production of biomethane. The alternating activated adsorption (AAA) process is implemented on full-scale at several wastewater treatment plants across Europe. However, there is a lack of full-scale studies of advanced carbon capture technology implementations in literature. This study demonstrates the ability of a full-scale AAA process to remove and redirect carbon in a region heavily influenced by tourism. Periods in high and off-season were compared to study the impact of tourism on the composition of the wastewater and the AAA-process. The wastewater characteristics of the high season differed significantly from the low season. During the high season, the PE increased by 37 %, total suspended solids went up by 75 % and chemical oxygen demand increased by 58 %, compared to the low season. Additionally, 80 % of the low volatile lipophilic substances (LVLS) measured were attributed to the impact of tourism. A mass-balance of primary treatment for chemical oxygen demand (COD) and LVLS was conducted for both trial periods. The primary treatment was able to eliminate 56 % of the COD and 62 % of the LVLS in the non-tourist season and 53 % of the COD and 54 % of the LVLS in the tourist season. The increased wastewater load was effectively managed in the AAA-process. Key process parameters like sludge settling characteristics, hydraulic retention time and total suspended solids removal rates remained stable during the high season in winter.

Elevated purification of urban rainwater runoff using a calamus constructed wetland with multi-layer carrier fillers

Urban water body pollution caused by storm-water runoff is increasingly serious due to rising global urbanization. We evaluated the effectiveness of a calamus vertical flow constructed wetland purifying urban runoff. This wetland was constructed using three filler layers of rare earth porcelain sand, ceramsite, and clinoptilolite respectively. The results revealed that under the optimal hydraulic load of 80 L/(m2·h), pollutants removal efficiency with the study wetland reached 89.9 %, 95.0 %, 84.7 %, and 76.2 % for the moderate rain runoff, in terms of COD (chemical oxygen demand), SS (suspended solids), TN (total nitrogen) and TP (total phosphorus) respectively. The removal rates of COD, SS, TN and TP by plants and the soil layer together were up to 64.9 %, 50.0 %, 58.1 %, and 28.6 %, respectively, while the rare earth porcelain sand layer had the highest contribution to the removal rate of TP (42.8 %), and the filler removal effect for phosphorus was more significant than that of plants and the soil layer. Although the influent water quality fluctuates with runoff from moderate to heavy torrential rain intensities, most of the effluent water meets the discharging standards. While the effluent quality of light rain runoff with high pollution load slightly exceeded the standards, it still removal rate as high as 88 %, 96.3 %, 73.3 %, 76.2 % for COD, SS, TN, TP.

Stormwater runoff pollution control performance of permeable concrete pavement and constructed wetland combined system: toward on-site reuse.

Urban waterlogging and the deterioration of receiving water quality caused by stormwater runoff have become increasingly significant problems. Based on the concept of combining grey and green infrastructure, a combined permeable concrete pavement (PCP) and constructed wetland (CW) system has been developed to treat stormwater runoff and enable on-site reuse. The results showed that the removal rate of suspended solids (SS) by PCP ranged from 96.61 to 99.20%; however, the chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations in the effluent did not meet the standards required for rainwater reuse. For the combined PCP-CW system, the removal rates of COD, TN and TP by the CW were 48.45-75.12%, 47.26-53.05%, and 59.04-75.28%, respectively, under different hydraulic loading (HL) rates; thus, the effluent TN concentrations did not consistently meet the reuse standards. Further optimization of aeration in different parts of the CW revealed that aeration in the middle and front sections of the wetland had the most significant effect on pollutant removal, under which the TN concentrations in the effluent met the standard required for reuse. The effluent from the combined PCP-CW system was able to fully meet the stormwater reuse standards under these optimized conditions, and the reuse of urban stormwater runoff can therefore be realized.

Treatment and prevention of pollutants in the wastewater from a scheelite and fluorite processing plant

Mineral processing wastewater contains high levels of chemical oxygen demand (COD), suspended solids (SS) and heavy metal ions, and its substandard discharge will pose a threat to the ecological environment and human health. In this study, a combined method of coagulation and Fenton oxidation was used to remove pollutants from scheelite and fluorite processing wastewater. The experimental results showed that the overall removal rates of COD, SS, Pb2+ and Zn2+ from the wastewater samples reached 88.41 %, 99.73 %, 99.09 % and 99.31 %, respectively, after stepwise treatment with poly ferric sulfate (PFS) coagulation and Fenton oxidation. The main contributors of COD in the wastewater samples were sodium oleate (NaOL) and benzohydroxamic acid (BHA). The maximum COD removal by PFS coagulation was >90 % for NaOL solution, but <45 % for BHA solution. The COD removal effect of Fenton process on NaOL solution was also better than that of BHA. This indicated that the removal effect of COD was not only related to the experimental conditions but also to the structure of organic compounds. Based on the above research, a monitoring and management system of pollutants was established, and the effective removal of pollutants was confirmed by industrial tests in a plant. This study provides a certain theoretical basis and technical support for the efficient treatment of mineral processing wastewater and is of great significance for the protection of the ecological environment around the mine.

The Application of Rubber Aggregate-Combined Permeable Concrete Mixture in Sponge City Construction

Permeable concrete is a new type of pavement material, which can effectively improve the urban flood discharge system, and is of great significance to the construction of sponge city. In order to optimize the use effect of permeable concrete and improve the application value of permeable concrete in permeable road engineering, the combination of rubber aggregate and permeable concrete is proposed, and the mix ratio of rubber permeable concrete mixture material is designed, which is applied to the engineering of pavement in Hunan Province, and its comprehensive pavement performance is analyzed and evaluated. The results show that the rubber permeable concrete has the best performance when the water cement ratio is 0.3, the designed porosity is 15%, the rubber particle size is 16 mesh, the rubber content is 15% and the coarse aggregate ratio is 4:6. The removal rates of suspended solids and metal pollutants are 0.65 and 0.72, respectively, which are increased by 0.23 and 0.19, respectively, compared with ordinary permeable concrete. This shows that rubber permeable concrete improves the ecological benefits of permeable concrete pavement, gives full play to the economic benefits of waste rubber products, reduces the construction cost of permeable concrete pavement, and provides assistance for promoting the construction of sponge city.

A Sustainable Approach for Removing Organic Pollutants from Food Processing Effluents Using Unmodified Cocopeat as an Adsorbent

Food production (chips) uses raw materials such as tapioca, cassava, banana, and many more, which contribute to excessive pollutants in the water. Thus, there is a need to treat effluent sufficiently to prevent undesired pollutants from being released into the receiving water bodies, such as rivers and agricultural drainage systems. This study aims to investigate the effectiveness of cocopeat in removing targeted parameters such as suspended solids (SS), chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), and total phosphorus (TP) from the chips processing effluent. Batch experiments were conducted to determine optimum operating parameters, including the adsorbent dosage, contact time, and shaking speed. This was done to identify the best removal rates of SS, COD, NH3-N and TP from effluent food processing samples taken from two different discharge points based on their usages. The experimental results show that at the optimum conditions of pH 7, cocopeat dosages of 800 mg/L, contact time of 30 minutes, and shaking speeds of 200 rpm, the unmodified cocopeat achieved 17.3% and 19.8% of SS removal, 35.5% and 28.9% of COD removal, 40.7% and 30.5% of NH3-N removal, and 53.5% and 59.2% of TP removal, from Point A and Point B effluent, respectively. Besides, the maximum adsorption capacity achieved by unmodified cocopeat towards SS (1.5-14.0 mg/g), COD (16.88-17.75 mg/g), NH3-N (0.31-0.32 mg/g) and TP (1.46-1.50 mg/g) are comparable to the adsorption capacities reported by previous researchers. This finding suggests that cocopeat could potentially replace the commercially developed adsorbents for the treatment. Furthermore, this study gave insights into the feasibility of sustainable treatment using cocopeat as an adsorbent for medium-strength effluent. However, it is suggested that further alteration of the cocopeat characteristics, either by chemical or physical modifications, and its sludge disposal methodcould be explored further to enhance the treatment performance.

Iron ore waste combined with lysozyme-producing bacteria to promote sludge reduction: Performance and mechanism

Due to the complex structure of sludge, sludge hydrolysis becomes the limiting factor for sludge digestion. In this study, a combined treatment system of lysozyme-producing bacteria and iron ore waste was established, and the lysozyme secreted by the enzyme-producing bacteria was used to realize the cracking of the sludge cell structure to achieve the purpose of reducing sludge. The results showed that the best hydrolysis effect could be achieved when the sintered ore dosage was 1.50 g L−1 and lysozyme inoculation dosage was 3 %. At 20 h, the release amount of soluble chemical oxygen demand (SCOD) was 1877.34 mg L−1, and the concentration of protein and polysaccharide increased by 226.64 and 114.51 mg L−1, respectively, which indicated that the sludge microorganisms released a large amount of intracellular substances. The removal rate of suspended solids (SS) concentration in the combined treatment system was 3.37 times that of the control group. The results of sludge morphology analysis showed that the sludge structure was destroyed and the particle size decreased. The addition of sinter reduced the Zeta potential of sludge, promoted electron transfer between microorganisms, and improved lysozyme production efficiency of enzyme-producing bacteria. Proteobacteria plays a dominant role in the combined treatment system. The combined treatment system significantly improved metabolic capacity and iron utilization capacity of the microbial community, which may be the mechanism for the combined treatment system to promote sludge reduction.

Evaluation of comprehensive benefits of sponge cities using meta-analysis in different geographical environments in China.

With the rapid progress in urbanization, frequent urban waterlogging and non-point source pollution are threatening the living and health of human beings. Sponge city construction has become an effective means to curb urban waterlogging. Although related studies have explored the comprehensive benefits of sponge cities, few studies have been conducted on the effects of different geographical environments on runoff control and suspended solid (SS) removal. Based on 76 cities with sponge cities in China, this study used the meta-analysis method to evaluate the relationships of climate, terrain, underlying surface conditions, and construction area with the increase in the total annual runoff control rate and SS removal rate. The results reveal that the runoff control benefit can be significantly improved by sponge cities under the combined conditions of average annual precipitation of approximately 1000 mm, high fractional vegetation cover, sufficient soil fertility, a terrain slope i of ≤2%, and a permeability coefficient of strata of 100-200 m/d, especially in northern China, where the weight representing the quantity of comprehensive benefits was calculated to be 25.5%. In addition, the study results assist in reforming unfavorable geographical environments in the construction of sponge city, thus providing more effective solutions for tackling SS pollution. The most significant benefits of SS removal were obtained in north central China, where the weight was 21.4%. This study comprehensively investigated the effects of geographical environmental factors on the comprehensive benefits of sponge city reflected by the improvement in the total annual runoff control rate and the SS removal rate. The results will provide guidance for the planning and design of global sponge cities and effectively optimize the practice, scale, and location of existing construction based on specific geographical environments.

Magnetic Hyperbranched Molecular Materials for Treatment of Oily Sewage Containing Polymer in Oilfield Compound Flooding.

With the continuous improvement in oilfield development and the application of tertiary oil recovery technology, the water content of oilfield-produced fluids has gradually increased, and a large number of oilfield sewage with complex components has also been produced after oil–water separation, and effective treatment is urgently needed. ASP flooding sewage contains alkali, various surfactants, polymers, microemulsion oil droplets, and solid impurities, which are difficult to be effectively treated by traditional water treatment agents and methods. In this study, aminopropyl triethoxysilane (APTES) was used to modify the nano-Fe3O4 coated with tetraethyl silicate (TEOS). The product was used as the ferromagnetic nano-core for the iterative reaction of Michael addition and ester amidation to synthesize a magnetic hyperbranched polyamide amine, and its performance in the treatment of ASP flooding wastewater was evaluated experimentally. For the preparation of APTES-modified Fe3O4@SiO2 (FOSN) product, TEOS was coated over Fe3O4 in an ethanol aqueous solution environment and then APTES was added dropwise. The first-generation branched product (1-FSMN) was obtained by the reaction of FOSN and methyl acrylate graft product (FOSN-M) with ethylenediamine, and the highest yield was 93.7%. The highest yield of the second-generation branched product (2-FSMN) was 91.6%. In this study, a composite flooding wastewater sample from a block in the Bohai oilfield was taken. The suspended solids content was 143 mg/L, the oil content was 921.09 mg/L, the turbidity was 135 NTU, and the zeta potential was −47 mV. The third-generation hyperbranched polymer (3-FSMN) and its quaternary ammonium salt (3-FSMN-Q) performed best in the appropriate dosage range, with the highest oil removal rate of 97%, suspended solid removal rate of 90.3%, turbidity reduction rate of 86.6% and zeta potential reduction rate of 88%. For 3-FSMN and its quaternary ammonium salt, the gravity/magnetic PAC compound treatment experiment was carried out. In the settlement time of only 5 min, 3-FSMN/PAC and 3-FSMN-Q/PAC can achieve the maximum oil removal rate of 87.1% and suspended solids removal rate of 87.3% for polymer containing wastewater from ASP flooding, and 86.3 and 86.0% for 120 mg/L. Its treatment capacity was much better than that of common treatment agent combination (CPAM/PAC).

A Study of Car Wash Wastewater Treatment by Cyclo-Flow Filtration

With the increase in transportation demand and facilities in this era and the significant improvement in people’s living standards, the annual production and sales of vehicles are steadily increasing. With this, the issues of car wash wastewater treatment and water pollution are becoming more and more serious. Car wash wastewater mainly comprises fine sand, slick oil, suspended solids (SS), and surfactants, and can be quantified as chemical oxygen demand (COD) on a normative basis. This study examines the use of cyclo-flow filtration with high filtrate flux to treat car wash wastewater to solve issue of limited space in metropolitan areas and increase the willingness of the industry to invest in car wash equipment to recover water resources. The average removal rates of SS and COD are about 81% and 43%, respectively. Compared with current technology, the price of recycled water can compensate for operating costs, requiring minimal operating space owing to the single-unit cyclo-flow filtration system.

Laboratory Investigation on Pollutant Removal Effect of Purification Materials for Porous Asphalt Pavement

Purification materials have been widely applied as filter media in best management measures including wetlands, bioretention systems, and so forth, whereas their application in permeable pavement is limited and needs further research. This paper aims to explore the feasible applications of water purification materials in permeable pavement materials and structures. Based on laboratory rainfall test and static adsorption test, the possible application of three types of water purification materials, including diatomite, quartz sand, and straw biochar, in porous asphalt pavement and their pollutant removal effect were investigated. The results show that the filter layers can effectively increase the total suspended solids removal rate to 60%–80%. And when the purification materials are applied as alternative fillers in porous asphalt mixture (PA), they can enhance the removal effect of dissolved pollutants, especially heavy metals, by their special chemical properties and the positive influence on microscopic pore structures of PA. The adsorption effect of PA on pollutants is closely related to the environment temperature. The PA adsorption of nutrients and Cu increases with the increase of temperature, but the adsorption effect of Cr is better at lower temperatures. The pseudo-first-order model and the pseudo-second-order model can properly describe the adsorption process of heavy metals Cu and Cr by PA, respectively. The purification schemes that present purification effects under different runoff pollution characteristics are recommended as well.

A New Strategy for Sponge City Construction of Urban Roads: Combining the Traditional Functions with Landscape and Drainage

Urban roads play a key role in sponge city construction, especially because of their drainage functions. However, efficient methods to enhance their drainage performance are still lacking. Here, we propose a new strategy to combine roads, green spaces, and the drainage system. Generally, by considering the organization of the runoff and the construction of the drainage system (including sponge city facilities) as the core of the strategy, the drainage and traffic functions were combined. This new strategy was implemented in a pilot study of road reconstruction conducted in Zhangjiagang, Suzhou, China. Steel slag was used in the structural layers to enhance the water permeability of the pavement and the removal of runoff pollutants. The combined effects of this system and of the ribbon biological retention zone, allowed achieving an average removal rate of suspended solids, a chemical oxygen demand, a removal of total nitrogen and total phosphorus of 71.60%, 78.35%, 63.93%, and 49.47%; in contrast, a traditional road could not perform as well. Furthermore, the volume control rate of the annual runoff met the construction requirements (70%). The results of the present study indicate that, combining the traditional basic functions of roads with those of landscape and drainage might be a promising strategy for sponge city construction of urban road.

Influence of ballasted material properties in enhancing the separation of high concentration suspended solids in coal mining water

With the continuous improvement and economic development of China’s coal mining industry, research on the characteristics of wastewater discharge has gained attraction in recent years. Ballasted flocculation technology, has been widely used in recent years. However, its effect on the settling velocity of the flocs in wastewater has not been quantified. This study aimed to screen optimal reaction condition for ballasted flocculation and to derive the settling velocity of the ballasted flocs under these conditions. The results showed that, the size of the ballasted material had no significant effect on the turbidity and suspended solids removal rate; however, the settling time was effectively shortened, and the turbidity removal rate could reach more than 95% within 15 s. Owing to the optimization of the reaction conditions, 90% of the flocs sizes were distributed in the 80–200 µm range. Moreover, the difference between the theoretical and the measured value of the ballasted flocculation was small, indicating that the derived formula could effectively quantify the settling velocity of the ballasted flocs under optimal conditions. These findings may serve as a critical reference for the treatment of high-suspended solids in coal mining water and have significant potential for engineering application.

Water Distribution and Silt Clogging in the Strong-Seepage Zone Infiltration Process of Yufuhe River from Yellow River Water Based on the Two-Dimensional Sand Tank Model

A two-dimensional sand tank experiment was designed to explore the mechanism of water distribution and silt clogging of Yellow River water whilst replenishing groundwater in ‘open window’ reach of the piedmont river and strong seepage area consisting of a gravel and karst layer from top to bottom. Water released through the reach was divided into surface, pore and fracture karst water, of which karst water was an effective recharge from the surface water. A reasonable released water plan is necessary in recharging to avoid invalid recharge. The karst water accounted for 60–70% of the amount of water released before clogging, and this value was reduced to approximately 10–20% whilst a thin clay layer formed from suspended particles on the surface layer of the medium after clogging. The removal rate of suspended solids along vertical and lateral directions in the medium can reach over 96%. The retained amount of suspended particles was mainly distributed on the surface and upper layer region of the medium. A rubber dam can improve effective infiltration whilst promoting suspended solid deposition in the medium. The fitting degree of the numerical simulation and measured results was above 0.9, which proves the reliability of the sand tank model results.

Effect of Media on Treatment of Settled Domestic Sewage Using Hybridized Anaerobic Baffled Reactors.(Dept.C)

This research work aimed at obtaining a low cost sustainable technology for domestic wastewater treatment for Egyptian rural areas. To make this come through, a high rate hybirdized anaerobic baffled reactor (HABR) was pilot tested for a period of about 18 months in order to assess the state of art and the technical and economic efficiency of this system. This pilot reactor consisted of four reactors with different media (HABR1, HABR2, HABR3 and HABR4) were constructed and each reactor had a total volume of 800 liters and consists of four compartments. Plastic media and gravel were used and had specific surface area of 100 and 80 m2/m3respectively. The average influent COD concentration was about 300 mg/1. The overall HRTs tested were 3.5, 2.5, 1.0 and 0.5 days with average influent organic loadings in the range from 0.05 to 0.25 Kg BOD5/m3.day. High substrate removal rates can be achieved in a HABR fed with low substrate levels of only 300 mg/lit of COD. At an HRT of 3.5 days, HABR) with plastic media gave an average BOD5 removal rate of 79% with an effluent of 25 mg/lit. This was the highest removal value recorded as the other reactors HABR2, HABR3 and HABR4 gave 60.5%, 71.5% and 75.6% respectively for the same HRT, In a likewise manner, the COD removal rates recorded at the same HRT were 85.7%, 80%, 83.3% and 85.7% respectively. Suspended solids removal rates were the highest and recorded a value of 90.3% for a HRT of 3.5 days for HABR1. At the same HRT the removal rates for HABR2, HABR3 and HABR4 were 76.8%, 86.5% and 89% respectively. For HABRI the HRT of 0.5 days. The highest COD value recorded was at a HRT of 0.5 days BODs removal rates dropped from 79% at a HRT of 3.5 days to about 50.5% at a HRT of 0.5 days. This was also the case with the other three reactors and the lowest removal rate recorded was 33.7% for HABR2 at for HABR2 with a value of 101.2 mg/lit. While the highest SS value recorded was 72.4 mg/lit with a percentage removal of 58.8% for HABR3 at a HRT of 0.5 days. This system provides potential attractive possibilities for application in small communities with a population of less than 5000 capita.

Combined dual-size foam glass media filtration process with micro-flocculation for simultaneous removal of particulate and dissolved contaminants in urban road runoff

In this study, a combined media filtration process with micro-flocculation (CMF) was developed, to simultaneously treat particulate and dissolved contaminants in urban road runoff. Dual-size foam glass media with stone and sand layers were applied and the efficiency of road runoff treatment was investigated according to filtration and micro-flocculation under various experimental conditions (stone/sand layer ratio, linear velocity, and coagulant types). Moreover, the removal efficiencies of suspended solids (SS), phosphorus, organic carbon, and heavy metals (Zn, Cu, Pb, Cd) by CMF were evaluated. The removal rate of SS was maintained to be above 84.1% for 1 h filtration by the dual-size foam glass, regardless of increasing pressure. The removal of phosphorus by micro-flocculation was more suitable in alum than ferric due to a higher initial floc growth rate and an increased particle size. The performance of the CMF was significantly improved over media filtration only process (MF) in removing both particulate and dissolved contaminants. The removal efficiency of all particulate pollutants by CMF was found to be more than 90%, and notably, the dissolved phosphorus, which was mostly not removed by MF, was also removed by 97.4%. Meanwhile, the backwash efficiency of CMF was half that of MF. Physical removal mechanisms, such as internal diffusion, dominated MF, whereas chemical removal mechanisms, such as adsorption and surface precipitation, dominated CMF. These results show the potential of the CMF process for the treatment of urban road runoff and identify the removal mechanisms of the filtration process that use micro-flocculation with dual-size foam glass.

Purification Effect of Sequential Constructed Wetland for the Polluted Water in Urban River

Constructed wetlands can play an active role in improving the water quality of urban rivers. In this study, a sequential series system of the floating-bed constructed wetland (FBCW), horizontal subsurface flow constructed wetland (HSFCW), and surface flow constructed wetland (SFCW) were constructed for the urban river treatment in the cold regions of North China, which gave full play to the combined advantages. In the Yitong River, the designed capacity and the hydraulic loading of the system was 100 m3/d and 0.10 m3/m2d, respectively. The hydraulic retention time was approximately 72 h. The monitoring results, from April to October in 2016, showed the multiple wetland ecosystem could effectively remove chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphate (TP), and suspended solids (SS) at average removal rates of 74.79%, 80.90%, 71.12%, 78.44%, and 91.90%, respectively. The removal rate of SS in floating-bed wetland was the largest among all the indicators (80.24%), which could prevent the block of sub-surface flow wetland effectively. The sub-surface flow wetland could remove the NH4-N, TN, and TP effectively, and the contribution rates were 79.20%, 64.64%, and 81.71%, respectively. The surface flow wetland could further purify the TN and the removal rate of TN could reach 23%. The total investment of this ecological engineering was $12,000. The construction cost and the operation cost were $120 and $0.02 per ton of polluted water, which was about 1/3 to 1/5 and 1/6 to 1/3 of the conventional sewage treatment, respectively. The results of this study provide a technical demonstration of the restoration of polluted water in urban rivers in northern China.