Sand Filtration Units Research Articles

Assessing operational issues in a modular sewage treatment plant and providing remedies via comprehensive modeling and simulation through GPS-X

In this study, an existing but faulty modular sewage treatment plant (STP) with a capacity of 100 m3/day has been modeled and assessed using GPS-X software, combined with sensitivity analysis to confirm an underlying but critical operational issue of an STP. Currently, the STP shows <5 % ammonia removal at an average influent ammonia concentration of 50 mg/L, along with the problem of partial BOD removal. The treatment units comprise an equalization tank, two moving bed biofilm reactors (MBBRs) in series, a tube settler and a sand filtration unit. Sensitivity analysis helped decipher the most influential kinetics/stoichiometric parameters, which assisted in achieving a precise model calibration. Post calibration, the modified model was re-simulated for each constituent treatment unit based on the mass balance of four major output parameters viz. NH4-N, biochemical oxygen demand, dissolved oxygen and alkalinity. Real experimental/measured values spanning over 8 months were analyzed during the calibration phases (including both static and dynamic calibration phases). The calibrated GPS-X model was simulated using various input factors to find a possible remedial solution and understand the critical limitation of the existing plant. As a remedial measure, a pre-anoxic tank with an operational volume of 15 m3 and a recirculation ratio of 3 was proposed for the existing STP. A proper experimental design and statistical tools further helped achieve the most optimum and techno-economically feasible solution for an MBBR-based biological treatment unit. This helped effectively manage wastewater pollution in a modular treatment system.

Removal and distribution of antibiotics and resistance genes in conventional and advanced drinking water treatment processes

With the extensive detection of antibiotics and antibiotic resistance genes (ARGs) in drinking water treatment plants, the safety of drinking water has received increased attention. Therefore, the distribution and removal of antibiotics and ARGs in drinking water systems require further investigation. In this study, nine typical antibiotics, nine ARGs, and one integron in two drinking water plants were investigated by high pressure liquid chromatography with tandem mass spectrometry and real-time quantitative polymerase chain reaction analyses. Sulfonamides were the dominant antibiotic in the two drinking water treatment plants (WP-A and WP-B). The removal effect of advanced water treatment on total antibiotic concentration was significantly higher than that of conventional treatment. Sul gene was the dominant gene in the raw water of the two plants. After undergoing different treatment units, the finished water in WP-A and WP-B exhibited Sul gene concentrations of 54.06 genes/mL and 67.9 genes/mL, respectively. In the conventional treatment process, adding a sand filtration unit before the flocculation unit can improve the removal efficiency of antibiotics and ARGs. In the advanced treatment process, the post ozonization unit using the strong oxidation of O3 could effectively remove antibiotics and ARGs. Although the activated carbon unit can effectively remove antibiotics, the removal effect of ARGs is poor. Chlorination has a poor effect on the removal of antibiotics, but it can effectively remove ARGs. This study can provide a basis for understanding the fate of antibiotics and ARGs in drinking water systems.

Monitoring of pesticides in surface water, pesticides removal efficiency in drinking water treatment plant and potential health risk to consumers using Monte Carlo simulation in Behbahan City, Iran

Excessive application of pesticides to control pests and weeds leads to contaminating bodies of water and health problems for consumers. The present study was designed to investigate the concentration of pesticides in raw water originated from the Marun River as well as the treated water of the drinking water treatment plant in Behbahan City. The efficiency of each treatment process was evaluated. Moreover, the health risks caused by detectable pesticides for consumers of treated water were assessed. The target pollutants were extracted using droplet liquid-liquid microextraction and detected by a gas chromatograph-mass spectrophotometer. The results showed relatively high mean concentrations of organophosphate pesticides ranging from 0.87 to 3.229 μg/L in the river water and low concentrations of organochlorine pesticides, except for 1,3-dichloropropene with the concentration of 3.58 μg/L. Alachlor had a rather high concentration (2.44 μg/L) in the river water. The concentration of pesticides in the drinking water had been reduced to an acceptable amount. The major part of pesticides removal occurred in coagulation-flocculation and rapid sand filtration units (87 %) due to the hydrophobic nature of pesticides and the use of GAC in the filtration unit. Based on the risk assessment estimates, the total hazard quotient (THQ) for all the pesticides was much less than one. The value of THQ was higher in younger individuals and children for all the given pesticides. The highest value of THQ in children was 0.2 which was attributed to aldrin. Similarly, the carcinogenic risk (CR) of aldrin for children and teenagers was in the unsafe range (more than 10−4) while the CR for other target compounds in all the age groups was negligible (10−4-10−6 or less). The high concentration of pesticides in the river water might be concerning and therefore selling and using pesticides, especially the banned ones, should be more regulated.

The efficiency of the sand filtration unit mixed with different packing materials in drain water treatment in Egypt

In an attempt to improve the quality of the agricultural drain in Egypt for its reuse again in the irrigation, low-cost solution such as sand filter along with/without other filtration media has been used in this research. As a result of that, pilot plant of sand filter mixed with other filtration media was tested for its ability to improve the sand performance in removing the suspended solids and organic matters from agricultural drain water of the Belbeis drain (in Sharkia governorate in Egypt). Sand only, sand mixed with sponge, sand mixed with activated carbon and sand mixed with ceramic cylinders have been tested to find the best media combination and optimum mixing sand/ medium ratio and optimum infiltration rate. The work has been done on four runs. It was found that sand mixed with ceramic cylinders gave the best removal efficiency with respect to total chemical oxygen demand and chemical oxygen demand for solution which were 77, 74%, respectively, whereas sand mixed with sponge had the best removal efficiency with respect to total suspended solids which was 89%. Also, all tested media combination had effluent quality that complied with Egyptian law 48 for the year 1982 regarding the disposal of wastewater into agricultural drains (chemical oxygen demand ≤ 80 mg/l, total suspended solids ≤ 50 mg/l).

Abundance and characteristics of microplastics in freshwater and treated tap water in Bangkok, Thailand.

Thailand is one of the largest contributors to plastic waste in the oceans. Since mismanaged plastic waste can enter the ocean via inland waterways, microplastic contamination in freshwater used for tap water production has been raised as a potential issue. This study was conducted to determine the abundance and characteristics of microplastics in freshwater and treated tap water in Bangkok. Freshwater and treated water were collected from the eastern and western water supply systems in the dry and wet seasons. The source waters of the eastern and western water supply systems are the Chao Phraya River and Maeklong River, respectively. Approximately 0.40-2.40 particles/L microplastics was determined in the freshwater samples. No significant differences in microplastic abundance with respect to water supply system or season were found. Approximately 82.1% of the total microplastics found in the freshwater were smaller than 300µm in size. The percentage contribution of various microplastic size ranges decreased with increasing size. The majority of microplastics found in freshwater were fragments (90.2%), colorless (64.3%), and made of polyethylene polymer (45.1%). Only the eastern water supply system was capable of removing microplastic particles (27.7%) from freshwater. The identification of microplastics larger than 100µm in size in the treated tap water indicated potential contamination from microplastics in the treatment system, particularly after the sand filtration unit. The major characteristics of the microplastics found in treated tap water were similar to those found in freshwater, with 85.6% fragments, 85.1% colorless, and 47.9% made of polyethylene polymer.

Waste Wash-Water Recycling in Ready Mix Concrete Plants

The management of waste wash-water (WWW) is one of the most significant environmental problems associated with ready-mix concrete production worldwide. The problems are exacerbated should it be disposed of in an inappropriate manner. This study evaluated the potential of WWW recycling in ready mix concrete plants in Jordan. A representative waste wash-water sample (400 L) was collected from a basin in a ready-mix concrete company. A pilot plant on the lab scale was fabricated and installed. The treatment system consisted of a concrete washout reclaimer, wedgebed slurry settling pond, slow sand filtration unit, and a neutralization unit. Water samples were collected from all stages of the pilot plant and analyzed. The collected waste wash-water samples were utilized for replacement of well water (mixing water) at various ratios. Fourteen concrete mixtures were produced and cast, as well as tested at various curing ages (7, 28, and 90 days). The results show that the raw WWW was not acceptable as mixing water even after dilution as it led to significant reductions in concrete compressive strength and low workability. However, the WWW from the settling pond, the filtered WWW and the filtered-neutralized WWW at dilution ratios up to 75% were shown to be potential alternatives to fresh water for ready-mixed concrete. Therefore, the current guidelines for mixing water quality should be revised to encourage the reuse of the WWW.

Potential of biological arsenite oxidation in sand filtration units at arsenic\u2013iron removal plants (AIRPs) in Bangladesh

This study is aimed to investigate biological oxidation of arsenic [As(III)] in sand component of arsenic–iron removal plant (AIRP). Water and sand samples were collected from the municipal and household AIRP units (MAIRP and HAIRPs) at Manikganj district, Bangladesh. These samples were analyzed using arsenic speciation cartridge with inductively coupled plasma-mass spectrometry for arsenic and iron detection and phylogenetic analysis based on aoxB gene sequencing. It was observed that arsenic concentration in the raw water, before and after sand filtration, ranged from 13.0–81.0 to 4.0–21.0 μg/L, respectively, which majorly contained reduced arsenic [As(III)] in the inlet and oxidized arsenic [As(V)] in the outlet. The results of our batch experiments showed that indeed sand unit of MAIRP oxidized As(III) with 36 g/h estimated biological oxidation potential which was considered enough to oxidize all the As(III) loading (6.3 g/h) in the influent. Additionally, bacterial arsenite oxidase gene (aoxB) was detected in the sand sample and has 80% sequence similarity with Polymorphum gilvum, an alphaproteobacteria on the phylogenetic tree. This study, therefore, revealed that AIRP sand units have enough potential of biological activity to ensure overall arsenic removal through As(III) oxidation. However, future research is necessary to unfold the basic mechanistic approach explored in this plant for further modification if need arises.

Textile Wastewater Treatment for Water Reuse: A Case Study

The reduced natural waters and the large amount of wastewater produced by textile industry necessitate an effective water reuse treatment. In this study, a combined two-stage water reuse treatment was established to enhance the quality and recovery rate of reused water. The primary treatment incorporated a flocculation and sedimentation system, two sand filtration units, an ozonation unit, an ultrafiltration (UF) system, and a reverse osmosis (RO) system. The second treatment included an ozonation unit, a sand filtration unit, and UF and RO systems. The color removal rate increased with the increasing ozone dosage, and the relational expression between the ozone dosage and color removal rate was fitted. Ozonation greatly reduced the color by 92.59 and 97.27 times during the primary and second ozonation stages, respectively. RO had the highest removal rate. The combined processes showed good performance in water reuse treatment. The treated, reused water satisfied the reuse standard and surpassed the drinking water standard rates for chemical oxygen consumption (CODcr), color, NH3-N, hardness, Cl−, SO42−, turbidity, Fe3+, and Cu2+. The operating cost of reuse water treatment was approximately 0.44 USD·m−3.

Special Issue on Wastewater Treatment and Reuse Technologies

Wastewater treatment allows for the safe disposal of municipal and industrial wastewater to protect public health and the ecosystem[...]

Multiple views of biological stability and optimized coagulation in the control of biostability in traditional water treatment processes: a pilot test

This study investigated biological stability in a pilot test of traditional water treatment processes in eastern China. The variations of assimilable organic carbon, biodegradable dissolved organic carbon, bacterial regrowth potential, and total phosphorus were analyzed, and the relationships among them were studied. High-purity aluminum sulfate was added as a coagulant, and the corresponding removal efficiencies of the coagulation–sedimentation unit and the sand filtration unit were evaluated. The experimental results indicate that the removal efficiencies of the dissolved organic carbon (DOC) and UV254 both increased as the alum dosages increased in the coagulation and sedimentation process. The removal efficiencies of the biostability indicators of the coagulation and sedimentation process were higher than those of the filtration treatment. The bacterial regrowth potential was correlated with DOC concentration, and the introduction of total dissolved phosphorus into the evaluation of biostability is recommended to help confirm the C:P ratio and to select the appropriate strategy for controlling bacterial regrowth. An explanation for the changes in biostability indicators is provided.

Rehabilitation by Chemical Treatment for Sand Media of Rapid Sand Filtration units for Sangli City

Rehabilitation by Chemical Treatment for Sand Media of Rapid Sand Filtration units for Sangli City

Evaluation of low cost water purification systems for humanitarian assistance and disaster relief (HA/DR)

Following a natural disaster, access to safe drinking water by the affected population is a high priority. Low cost water purification systems, which can be used for both short-term (immediate) and long-term (sustainable) response to serve the needs of the affected communities, are ideal for these scenarios. The University of Hawaii has developed three low cost water purification technologies for use during humanitarian assistance and disaster relief (HA/DR) missions. A UH team participated in joint USA and partner nation training exercises, such as Crimson Viper 2010 and 2011, organized by the Marine Corps Forces Pacific Experimentation Center (MEC) in Sattahip, Thailand, to demonstrate the effectiveness of these technologies to purify water from local sources. Three technologies were selected for Crimson Viper 2010: (1) a backpack filter unit, (2) a bicycle pump powered reverse osmosis (RO) unit, and (3) a model slow sand filtration unit. For Crimson Viper 2011, improved versions of the backpack and RO units were deployed. This article discusses and evaluates the results obtained during the demonstration of the three technologies at these exercises.

Comparison of optional process configurations and operating conditions for ceramic membrane MF coupled with coagulation/flocculation pre-treatment for the removal of NOM in drinking water production

The increase of Natural Organic Matter (NOM) in natural water sources, partly caused by progressing climate change issues, is a growing concern for drinking water production. In recent years, membrane technology like Reverse Osmosis (RO) or Nanofiltration (NF) has been successfully applied as a robust solution for NOM removal to produce potable water. However, coagulation/flocculation pre-treatment, combined with Microfiltration (MF) ceramic membrane filtration is nowadays seen as an alternative, less-energy-consuming membrane process for NOM removal. In this study different coagulants have been used under varying coagulation/flocculation conditions to investigate the respective impact on membrane filtration performance. Three alternative coagulation/flocculation configurations were compared. It is shown that NOM was efficiently removed independently on the chosen configuration or coagulant type. Similar and low membrane fouling rates were observed for all tests. Residual metal concentration was found to be the limiting permeate quality parameter, which limits the options of operating conditions. Furthermore, the compact inline pipe flocculator configuration has the potential of designing more compact full-scale units, using less space compared to conventional sand filtration units or even membrane filtration plants using classical tank coagulation/flocculation configurations.

Biodiversity of amoebae and amoebae‐resisting bacteria in a drinking water treatment plant

The complex ecology of free-living amoebae (FLA) and their role in spreading pathogenic microorganisms through water systems have recently raised considerable interest. In this study, we investigated the presence of FLA and amoebae-resisting bacteria (ARB) at various stages of a drinking water plant fed with river water. We isolated various amoebal species from the river and from several points within the plant, mostly at early steps of water treatment. Echinamoeba- and Hartmannella-related amoebae were mainly recovered in the drinking water plant whereas Acanthamoeba- and Naegleria-related amoebae were recovered from the river water and the sand filtration units. Some FLA isolates were recovered immediately after the ozonation step, thus suggesting resistance of these microorganisms to this disinfection procedure. A bacterial isolate related to Mycobacterium mucogenicum was recovered from an Echinamoeba-related amoeba isolated from ozone-treated water. Various other ARB were recovered using co-culture with axenic Acanthamoeba castellanii, including mycobacteria, legionella, Chlamydia-like organisms and various proteobacteria. Noteworthy, a new Parachlamydia acanthamoebae strain was recovered from river water and from granular activated carbon (GAC) biofilm. As amoebae mainly multiply in sand and GAC filters, optimization of filter backwash procedures probably offers a possibility to better control these protists and the risk associated with their intracellular hosts.

A feasibility study of industrial wastewater recovery using electrodialysis reversal

A wastewater reclamation and reuse “mini-plant” was established at the site of China Steel Corporation (CSC) wastewater treatment plant. The purpose of the mini-plant is to demonstrate the technical and economical feasibility of electrodialysis reversal (EDR) process. The mini-plant includes a sand filtration unit and an EDR unit which has a daily treatment capacity of 350 CMD. Raw wastewater had an averaged conductivity of 3860 μS/cm, pH between 7.7 and 8.3, and COD between 30 and 70 mg/L. When the EDR unit operates at a 75% of water reclamation rate, 92% of desalination rate, 98% of chlorine ion removal, 80% of sulfate removal, 99% of calcium ion removal, and 51% of COD removal rate can be achieved. The water quality of product stream is 305 μS/cm for conductivity, 13 mg/L for chlorine ion, 86 mg/L for sulfate, 1.4 mg/L for calcium ion, and of 20 mg/L for COD concentration. Operation cost of the EDR mini-plant was also estimated in this project. The electricity required for electrodes power supply and pumping is 0.85 kW h per cubic meter of treated water. Total operation cost including electricity fee and chemical cost is about $0.146 per cubic meter of treated water.

Influence of biofilms on the movement of colloids in porous media. Implications for colloid facilitated transport in subsurface environments

Colloid transport through porous media can be influenced by the presence of biofilms. Sterile and non-sterile sand columns were investigated using Laponite RD as model colloid and a highly mucoid strain of Pseudomonas aeruginosa as model biofilm former. Laponite RD was marked specifically by fluorescent complexes with rhodamine 6G. Breakthrough curves (BTCs) were used as parameters for determination of colloid transport characteristics. In the sterile columns, the colloid was mobile (collision efficiencies from 0.05 to 0.08) both after the presence of Na + and Ca 2+ ions followed by deionised water influent. In the biofilm-grown column, the same treatment did not result in colloid retention in the case of Na + exposure, but in altered or enhanced colloid transport. In the case of Ca 2+ ions exposure, colloid retention increased with biofilm age. After 3 weeks, almost complete retention was observed. Similar observations were made in columns packed with material from slow sand filtration units. These data reveal the complex interactions between biofilms, cations and colloid transport. Changes in the electrolyte composition of water percolating the subsurface can frequently occur and will result in different colloid transport characteristics with regard to the dominating species of ions and the relative abundance of microbial biofilms. This has to be considered when modelling colloid transport through the subsurface.

The Use of Limestone Bed Filtration for the Treatment of Ferruginous Groundwater

AbstractA pilot plant, consisting of limestone bed and sand filtration units, has been built 15 km south of Cairo to serve about 400 people. The plant comprises three limestone filter units (operated in series) and two sand filters.Operation of the pilot plant has shown that a packed limestone filter unit is a simple and cheap method of removing iron from ferruginous groundwater. The results demonstrate an iron removal rate of about 60% after passing through one 1.15−m deep limestone filter operating with a surface loading rate up to 1.4 m3/m2. h. The overall iron removal after one limestone filter followed by sand filtration was more than 90%.

Aeration by conventional cascades in arid weather

Abstract Oxygen requirements in the water treatment system are the result of demands to remove undesirable materials such as carbon dioxide, hydrogen‐sulfide and oxidizable minerals in waters. The oxygen content depends on water supply sources. Changing oxygen requirements resulting from water sources must be correctly estimated by designers. In addition to that, weather conditions of the region surrounding the water treatment plant must be known, as well as properties of the reactor type selected. In this research, a pilot plant including aeration (cascades type) and slow sand filtration units was constructed in order to study the treatability of ground water in the Fezzan Area (Libya). Aeration experiments were carried out in both Winter and Summer. The dissolved oxygen concentration and the temperature of the source and effluent streams were measured. By the evaluation of the data obtained, an estimation formula was developed to use for possible requirements at warmer temperatures.

Aeration and slow sand filtration in small systems

Abstract Treatment technologies for small systems should have lower construction and operation cost, lower maintenance and labor requirements as well. The quality of groundwater in the Fezzan area of Libya for drinking purposes is not acceptable when compared to the quality of standards given by WHO. Hence, the groundwater has to be treated before being used for drinking purposes. In the Sahara Desert there is a tremendous amount of sand which is suitable for slow sand filtration and rapid sand filtration within the water treatment objectives. In this study, the selected treatment system of the groundwater contains aeration and slow sand filtration units. This small system was constructed as a pilot plant at the campus of Higher Institute of Technology Brack‐Libya. This system which was installed and succesfully operated has been proved to be an effective and appropriate treatment technology. After these results, it has been shown that drinking water for the residential areas in the Al Shati region or any...

Biological Treatment of Groundwater in Basins with Floating Filters–I. Test Arrangements and General Results

The research project deals with biological treatment of groundwater, in particular, the removal of iron and manganese in basins equipped with, primarily, floating coarse-grained filters that constitute the pre-treatment unit. This unit, which complements the sand filter, is actually the principal treatment unit. In the “pre-treatment unit” water flows recurrently through the floating filter and through the boundary surface between air and water. This promotes chemical oxidation, creates favourable conditions for biological activity and accelerates the sedimentation of the precipitate on the bottom of the basins. In the pre-treatment unit the precipitation process for iron in the different test plants (7 plants) started effectively within 1 to 5 months, the reduction being 82-95%. For manganese the reduction was from 0 to 83 %. After the sand filtration unit iron was almost totally removed and at three test plants also the manganese reduction was at least 80%. At some of the plants the said time was not sufficient to get the precipitation process for manganese going. The groundwater treatment result is influenced, in addition to technical arrangements, in a decisive way by the physico-chemical and microbiological quality of the raw water.