Slow Sand Filtration Research Articles

Visualization of the Microbial Community and Elemental Mapping of Anadara granosa Media Used in a Slow Sand Filter Using a SEM-EDS

The removal of contaminants in slow sand filters occurs mainly in the biofilm above the filter media called schmutzdecke - a thin biological layer consisting of various microbial communities of algae, bacteria, diatoms and zooplankton. The layer formed ripens along with continuous straining and ads orption mechanism of impurities in raw water. Anadara granosa shell has been broadly used as an adsorbent to trap organic matter, turbid particles and heavy metal ion in raw wastewater. This research is aimed to visualise the microbial community grown on schmutzdecke in 2-weeks ripening period and maps the elemental characterisation of a grinded Anadara granosa shell media after the ripening period using a Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM-EDS). The result shows that mostly algae and diatoms have been recognised without species identification. Calcium (67%) and oxygen (21%) dominate the major chemical element contained in grinded Anadara granosa shell media, indicating that calcium carbonate and calcite can replace conventional sand as a more-efficient slow sand filter media, with longer maturing period. Such result can lead to further research about the increase of clamshell usage as a slow sand filter media to treat any types of wastewater, especially in rural areas in developing countries.

Sustaining Calcutta for 150 years: Pulta–Tallah water supply system, India

Asia’s first surface-water-based supply system became operational in 1868 to quench the increasing demand of Calcutta, India, an emerging commercial hub of the nineteenth century. Although the city was next to the River Hooghly, its original supply was framed to draw water from 22 km upstream at Pulta. Raw water was treated and then transferred to Tallah, near the northern fringe of the city, for subsequent distribution by pumping. Thus, the Pulta–Tallah system started operation with a 27·3 million litres per day (mld) capacity with slow sand filters. Later, a giant 41 million litre overhead reservoir with 29·6 m staging was introduced at Tallah in 1911, the largest in the world. It acted as a balancing reservoir, receiving water during off-peak hours, storing and then supplying during maximum demand, to insulate the pumps against fluctuating downstream demand. There are six transmission mains transferring water from Pulta to Tallah. Now, this water system has an installed capacity of 1182 mld and employs advanced treatment technologies. This paper summarises the history of the inception and progressive development of the Pulta–Tallah system, which still serves more than half of Calcutta and stands out as an epitome of a sustainable urban supply system.

Research on Slow Sand Filtration Simulation System for Salty, Phosphate and Zinc Removal

The research focuses on slow sand filtration (SSF) simulation system for salty, phosphate and zinc removal. Salty, phosphate and zinc are all the polluted compostions of rainwater runoff. SSF system is an ideal way to purify the rainwater runoff due to its simplicity of construction and low cost. The paper also introduces the practical applications of SSF system nowadays. With the remarkable economic and human pupulation developments, our world faces the challenges of water scarcity. SSF system has great potential in filtering rainwater to provide no-potable water even potable water.

Modeling Improved Performance of Reduced-Height Biosand Water Filter Designs

Point-of-use biosand water filters are widely distributed in undeveloped or developing regions due to their water treatment success and low-cost design, but two gaps remain in the basic technology: (1) the filter body is oversized relative to its contaminant removal performance, and (2) the heavy design largely excludes difficult to reach locations in need of clean water solutions. Here, we model design modifications to the v.10 Centre for Affordable Water and Sanitation Technology biosand filter using a reduced filter height, increased biolayer area, and conserved reservoir volume. We compare the hydraulic characteristics (dynamic velocity and head pressure) and percent contaminant removal of bacteria Escherichia coli and virus MS2 of the modified designs to the traditional control design using a finite element approximation of Darcy’s law with discrete time steps and a slow-sand filtration model. We demonstrate that a reduced-height design has a greater impact on contaminant removal compared to the traditional design (largely due to the increased residence time from the decreased flow rate inside the filter). For example, our 70% reduced-height filter design removed 99.5% and 73.93% of E. coli and MS2, respectively, where the traditional filter design removed 62.81% and 27.6%, respectively. Reduced-height designs should be pursued as a viable solution to improve filter performance while allowing for alternative construction techniques with greater end-user accessibility compared to the traditional design.

Drinking water treatment by multistage filtration on a household scale: Efficiency and challenges

Universalising actions aimed at water supply in rural communities and indigenous populations must focus on simple and low-cost technologies adapted to the local context. In this setting, this research studied the dynamic gravel filter (DGF) as a pre-treatment to household slow-sand filters (HSSFs), which is the first description of a household multistage filtration scale to treat drinking water. DGFs (with and without a non-woven blanket on top of the gravel layer) followed by HSSFs were tested. DGFs operated with a filtration rate of 3.21m3m-2.d-1 and HSSFs with 1.52m3m-2.d-1. Influent water contained kaolinite, humic acid and suspension of coliforms and protozoa. Physical-chemical parameters were evaluated, as well as Escherichia coli, Giardia spp. cysts and Cryptosporidium spp. oocyst reductions. Removal was low (up to 6.6%) concerning true colour, total organic carbon and absorbance (λ=254nm). Nevertheless, HMSFs showed turbidity decrease above 60%, E.coli reduction up to 1.78 log, Giardia cysts and Cryptosporidium oocysts reductions up to 3.15 log and 2.24 log, respectively. The non-woven blanket was shown as an important physical barrier to remove solids, E.coli and protozoa.

Mobility and redox transformation of arsenic during treatment of artificially recharged groundwater for drinking water production

In this study we investigate opportunities for reducing arsenic (As) to low levels, below 1 μg/L in produced drinking water from artificially infiltrated groundwater. We observe that rapid sand filtration is the most important treatment step for the oxidation and removal of As at water treatment plants which use artificially recharged groundwater as source. Removal of As is mainly due to As co-precipitation with Fe(III)(oxyhydr)oxides, which shows higher efficiency in rapid sand filter beds compared to aeration and supernatant storage. This is due to an accelerated oxidation of As(III) to As(V) in the filter bed which may be caused by the manganese oxides and/or As(III) oxidizing bacteria, as both are found in the coating of rapid sand filter media grains by chemical analysis and taxonomic profiling of the bacterial communities. Arsenic removal does not take place in treatment steps such as granular activated carbon filtration, ultrafiltration or slow sand filtration, due to a lack of hydrolyzing iron in their influent and a lack of adsorption affinity between As and the filtration surfaces. Further, we found that As reduction to below 1 μg/L can be effectively achieved at water treatment plants either by treating the influent of rapid sand filters by dosing potassium permanganate in combination with ferric chloride or by treating the effluent of rapid sand filters with ferric chloride dosing only. Finally, we observe that reducing the pH is an effective measure for increasing As co-precipitation with Fe(III)(oxyhydr)oxides, but only when the oxidized arsenic, As(V), is the predominant species in water.

Behavior of schmutzdecke with varied filtration rates of slow sand filter to remove total coliforms

The previous research showed that slow sand filtration (SSF) can remove the total coli by approximately 99% because of the schmutzecke layer in the filter. The presented study aimed to complete the previous research on SSF, especially on the schmuztdecke layer mechanism, to remove total coli. Total coli is a parameter of water quality standard in Indonesia, and the behavior of schmutzdecke affects the total coli removal. In the present study, the raw water from Amprong River was treated using horizontal roughing filter (HRF) and SSF. The variations in SSF rate used were 0.2 and 0.4 m/h. Total coliforms were analyzed using the most probable number test, and schmutzdecke visualization was conducted through scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX). The best coliform concentration in water treated by the combination of HRF and SSF was 4,386 colonies per 100 mL of sample using the filtration rate of 0.2 m/h, and its removal efficiency was 99.60%. However, the quality of water treated by the combination of HRF and SSF did not meet the drinking water quality standard because the removal of total coli must be 100%. The SEM–EDX visualization results in schmutzdecke showed that the average bacteria in the schmutzdecke layer were small, white, opaque, and circular, with entire edge and flat elevation. The Gram test results showed that the schmutzdecke bacteria consisted of Gram-positive and Gram-negative bacteria with basil as the common cell form.

Water quality in recirculating aquaculture system using woodchip denitrification and slow sand filtration

In recirculating aquaculture system (RAS), ammonium excreted by the fish is typically transformed to less toxic nitrate by microbial activity in bioreactors. However, nitrate-nitrogen load can be harmful for the receiving water body when released from the RAS facility. A new type of water treatment system for a RAS was designed, including a passive woodchip denitrification followed by a sand filtration introduced into a side-loop of an experimental RAS, rearing rainbow trout (Oncorhynchus mykiss). In the process, woodchips acted as a carbon source for the denitrification, aiming at a simultaneous nitrogen removal and reduction of water consumption while sand filtration was used to remove organic matter and recondition the circulating water. A variety of chemical analyses and toxicological tests were performed to study the suitability of the process and to ensure the absence of harmful or toxic substances in the system. The results did not show increased toxicity, and no increased mortality was reported for the raised species. After the start-up of the system, the concentrations of fatty acids (e.g., hexadecanoic acid <LOD-1.21 mg L−1) and heavy metals (e.g., Cd < LOD-0.45 μg L−1, Pb < LOD-14 μg L−1) remained at very low levels and below those of known toxic effects. In the beginning of the experiment, good denitrification efficiency was achieved, but it declined after 1 month, showing the need for improved stability and dimensioning of the application.

Ripening of household slow sand filter by adding fish food

Abstract Vulnerable communities can improve their quality of life using point-of-use water treatment technologies. Among these technologies, household slow sand filters (HSSF), which are filters adapted to domestic operations, stand out as one of the most effective and sustainable alternatives. However, some technical issues are not fully understood, such as the ripening process, which may take a long time to take place. In this context, this research evaluated the performance of a HSSF, in real scale and operated in continuous flow when a source of nutrients (fish food) was added to influent water, as a potential ripening agent. Physicochemical and microbiological parameters were evaluated to estimate the filter efficiency. According to the results, the HSSF reached a partial ripeness level in a short time with target parameter reduction in filtered water. Nevertheless, the instability observed in the filtered water quality reveals the significant health risks associated with human consumption when the HSSF is not yet ripened.

Influence of Gravel as Protection Layer on the Filter Run Time

Abstract: Since the beginning of the usage of slow sand filter (SSF) as one of the water treat-ment technologies, studies on how to enhance the performance have been conducted to date. One of the limitations in the current knowledge is regarding the method to increase the filter run time. The addition of protection layer may extend the filter run time. This paper focuses on the influence of gravel as the protection layer to the filter run time and turbidity removal. Gravel was chosen as the material of protection layer because of its low-cost and availability. A system-atic investigation by comparing only one different factor within the filter, which was protection layer, was conducted under the laboratory scale. The experimentconsisted of two filter columns namely K1 and K2. Both filters were constructed using the same filter depth, type of sand, and grain size distribution. The protection layer was added to filter K1, but not to filter K2. The sol-ids penetration and the increase of filter head loss wasused to evaluate the filter run time. A sta-tistical analysis was also carried out to examine the difference on the turbidity removal from both filters. The findings showed that by adding the protection layer, the filter run time could be extended up to 70%. Regarding to the turbidityremoval, there was insignificant difference between two filters.

Studying the performance of an Activated Carbon Filter using almond shell

Using new technologies and sustainable methods to obtain safe and clean water is considered one of the most important aims. In this work, almond shells have been used to prepare an activated carbon (AC) filter. Two types of sand filter media were used to simulate slow and rapid sand filters. Samples of raw water from Tigris River were taken, and the following parameters were studied (pH, turbidity, electrical conductivity (EC), total dissolved solids (TDS), sulphate and heavy metals (Iron(Fe), copper(Cu) and zinc(Zn)). Results showed that replacing sand with AC was better in the removal of Fe and Zn, when a slow sand filter was used the removal was 99% for both of them, while the enhancement in the removal seems to be small when the rapid sand filter was used.

Slow sand filtration of raw wastewater using biochar as an alternative filtration media

The efficiency of anaerobic biofilters (AnBF) as low-cost wastewater treatment systems was investigated. Miscanthus-biochar was used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal wastewater treatment plant was stored in a sedimentation tank for two days to allow pre-settlement of wastewater particles. Subsequently, wastewater was treated by AnBFs at 22 °C room temperature at a hydraulic loading rate of 0.05 m∙h−1 with an empty bed contact time of 14.4 h and a mean organic loading rate of 509 ± 173 gCOD∙m−3∙d−1. Mean removal of chemical oxygen demand (COD) of biochar filters was with 74 ± 18% significantly higher than of sand filters (61 ± 12%). In contrast to sand filters with a mean reduction of 1.18 ± 0.31 log-units, E. coli removal through biochar was with 1.35 ± 0.27 log-units significantly higher and increased with experimental time. Main removal took place within the schmutzdecke, a biologically active dirt layer that develops simultaneously on the surface of filter beds. Since the E. coli contamination of both filter materials was equal, the higher removal efficiency of biochar filters is probably a result of an improved biodegradation within deeper zones of the filter bed. Overall, performance of biochar filters was better or equal compared to sand and have thus demonstrated the suitability of Miscanthus-biochar as filter media for wastewater treatment.

The design of slow sand filter with a media of silica sand and granular activated carbon to eliminate iron, manganese, and fecal coliform contents for the Faculty of Nursing in Universitas Indonesia’s CWPS

The Faculty of Nursing of Universitas Indonesia in Depok uses groundwater as the source of clean water in a large amount: 2.115.240 liters in 2018 and 22.010.960 liters in 2019. One of the alternatives for reducing groundwater use is to utilize surface water in the surrounding area of the campus, such as Lake Agathis. For the lake water to be used as the source of clean water, it needs to be processed first using a clean water provision system (CWPS). The CWPS is designed to contain two slow sand filter units, with the media consisting of 60 cm-thick silica sand and 40 cm-thick granular activated carbon in each unit. The CWPS is also equipped with one unit of shore intake, two units of suction well, one transmission duct, one unit of disinfectant and reservoir, and two filter media cleaning units. Based on a literature review from several journals and the results from this experiment, the designed slow sand filter with the previously determined thickness can reduce iron contents by 95,07%, manganese contents by 97,09%, and fecal coliform contents by 99%. The designed CWPS can serve the needs of clean water of the faculty described before with a debit of 3,8 L/s until the year 2042.

Peat Water Purification by Hybrid of Slow Sand Filtration and Coagulant Treatment

Peat Water Purification by Hybrid of Slow Sand Filtration and Coagulant Treatment

A Comparison of Irrigation-Water Containment Methods and Management Strategies Between Two Ornamental Production Systems to Minimize Water Security Threats

Water security in ornamental plant production systems is vital for maintaining profitability. Expensive, complicated, or potentially dangerous treatment systems, together with skilled labor, is often necessary to ensure water quality and plant health. Two contrasting commercial ornamental crop production systems in a mesic region are compared, providing insight into the various strategies employed using irrigation-water containment and treatment systems. The first is a greenhouse/outdoor container operation which grows annual ornamental plants throughout the year using irrigation booms, drip emitters, and/or ebb and flow systems depending on the crop, container size, and/or stage of growth. The operation contains and recycles 50–75% of applied water through a system of underground cisterns, using a recycling reservoir and a newly constructed 0.25 ha slow-sand filtration (SSF) unit. Groundwater provides additional water when needed. Water quantity is not a problem in this operation, but disease and water quality issues, including agrochemicals, are of potential concern. The second is a perennial-plant nursery which propagates cuttings and produces field-grown trees and containerized plants. It has a series of containment/recycling reservoirs that capture rainwater and irrigation return water, together with wells of limited output. Water quantity is a more important issue for this nursery, but poor water quality has had some negative economic effects. Irrigation return water is filtered and sanitized with chlorine gas before being applied to plants via overhead and micro-irrigation systems. The agrochemical paclobutrazol was monitored for one year in the first operation and plant pathogens were qualified and quantified over two seasons for both production systems. The two operations employ very different water treatment systems based on their access to water, growing methods, land topography, and capital investment. Each operation has experienced different water quantity and quality vulnerabilities, and has addressed these threats using a variety of technologies and management techniques to reduce their impacts.

The attached microorganisms on the sand grain surfaces at the Slow Sand Filters

This study was carried out in order to investigate mainly the populations of different microorganisms attached to the sand grain surfaces in the slow sand filter beds at Ashford Common Water-treatment works in London area, U.K. using the mechanical shaking technique. It was proved that this technique is one of the more suitable and safe means in extracting microorganisms attached to particles such as sand grains and/or clay particles by applying the scanning electron microscope technique. The scanning micrographs illustrate that there is a direct proportional declination for the numerical densities of the microorganisms at different depths and various time intervals of shaking, while illumination intensities showed a conspicuous pattern particularly in case of complete shading. Simultaneously, It was too difficult to have any other organisms particularly protozoa in the same micrographs which might be referred to the exaggerated abundance of the algal layer Schmutsdecke, the presence of certain predators (rotifers, chironomid and insect larvae) and the presence of a very weak attachment between protozoa and sand grains.

Assessment of drinking water quality along Port Said Canal treatment plants, Suez Canal corridor, Egypt

Port Said Canal is one of the man-made Nile branches in Egypt that gain its water supply via the Ismailia Canal. The canal extended parallel to the Suez Canal navigation route providing the surrounding region the necessary drinking and irrigation waters. The water treatment plants along the canal use the surface water as a crude supply without preliminary pre-filtration process, and chlorination is applied in two phases, which may impose some health hazards. The study aims to ensure that the finished water is safe to drink and meet the international drinking water regulations. The public water purification systems in four treatment plants along Port Said Canal were tested for their efficiency and chlorination by-products. Raw and treated waters in these plants were analyzed for organic, toxic, trace, and heavy elements. Flow measurements were implemented at five sections along the main canal course during the summer and the winter seasons. Results indicated that the treated water suffers from low filtering effectiveness and exceeds the drinking water standards for the trihalomethane species. Furthermore, the change of canal flow from influent to effluent conditions during the winter season increases the contaminants’ concentrations. Also, the heavy metal concentrations in the treated water samples from all treatment works were much higher than that of the raw water samples, especially for those higher in suspended particulate matter. The study proposed a better purification system including, sedimentation and gravel pre-filtration combined with slow sand filtration and underground water passage for the elimination of the existing pollution problems.

Implementation of Fine Sand’s Capillary Force to Filter Polluted Water: A Study on Change of Overflow Media Height to the Debit and Quality of Filtered Tofu Liquid Waste

Four identically designed and constructed Capillary-Gravitational Slow Sand Filter (SSF) with different in its overflow media height were parallelly operated to filtered tofu liquid waste for the purpose to identify responses of debit and quality of permeate with the change of overflow media height. The experiment was conducted following 4x4 LS with the overflow media height as the treatment. Besides the debit for clear and polluted water, samples of the liquid waste and the permeate were taken and analysed for TSS, Turbidity, pH, BOD and COD. Result of analysis showed that debit of SSF was 182.6 -252.1 ml/minute for clear water; 81.3 – 153.5 ml/minute for tofu liquid waste; TSS 7.5 – 20.5 mg/L; Turbidity 0.58 – 3.84 NTU; pH 6.8 – 7.2; BOD 1.7 – 35.4 mg/L; COD 3.8 – 108.0 mg/L with removal efficiency more 96% when overflow media 4 cm or more. In conclusion, the SSF Grapilar reduced when it was used to filter polluted water. In terms of pollutant removal, SSF Grapilar was effective; it was able to remove more than 95% of TSS, Turbidity, BOD, COD and neutralized permeate of tofu liquid waste when the overflow media height was 4 cm or more.

Household slow sand filters in intermittent and continuous flows to treat water containing low mineral ion concentrations and Bisphenol A

Household slow sand filter (HSSF) has been used as an alternative to drinking water treatment in rural communities worldwide; however, its performance to treat influent water with quality similar to rainwater still needs further studies. Rainwater presents low pH and slight mineral ion concentrations, an aspect that can modify the filter media and consequently the HSSF efficiency. Furthermore, house roofs used in rainwater harvesting can be made of plastic. Therefore, it can introduce chemicals such as Bisphenol A (BPA) in the water. In this context, two pilot-scale HSSFs operated in continuous and intermittent flows were evaluated to treat water containing BPA and low mineral ion concentrations in order to assess the filter performance. Filter media leaching was noticed in the trials; thus, filter media and construction material selection must be carefully evaluated to eliminate risks of pollutant occurrence in drinking water. Operational differences between continuous and intermittent flows influenced the HSSF efficiency for BPA and DOC removals; even so, the filters’ performance was low probably due to the slow schmutzdecke development. According to tracer test results, HSSF can be classified as a plug flow reactor and strategies to improve its hydraulic performance are not required.

Teknologi pengolahan air gambut menjadi air bersih dengan sistem koagulan dan filtrasi di Desa Buluh Cina, Kecamatan Siak Hulu, Kampar

The abundant peat water in Buluh Cina Village, Siak Hulu Subdistrict, Kampar is a natural potential that can be used for cooking and bathing purposes by processing peat water into clean water that is suitable for consumption. The purpose of this service activity is to treat peat water into clean water. The method used in this service activity is using coagulant and filtration technology. The optimal filtration and coagulant media used for peat water treatment consists of biosand filters with two media namely pumice and quartz sand. The dedication results reduce turbidity and color of peat water and reduce organic content, so that peat water is processed into clean drinking water. The lowest pH value before filtering is equal to 5.93 and the highest pH is found before filtering which is 6.23. This means that before filtering peat water is weak acidic. The lowest sample results after filtration with a slow sand filter that is equal to 6.42 and the highest pH after filtration of 7.5, which means that water is weakly basic. A good pH limit for water is 6.5 to 8.5 so this service proves that slow sand filters are considered effective enough to optimize water pH. Total dissolved solids (TDS) is one of the parameters for determining water quality, TDS shows the amount of solute solids in water. The result of peat water TDS is that the lowest TDS value before filtration is 46 mg / L and the highest TDS is found before filtering which is 49 mg/L. The lowest sample results after filtration with slow sand filter is 49 mg / L and the highest TDS after filtering is 83 mg/L.