Small-scale Wastewater Treatment Research Articles

Using Surrogate Parameters to Enhance Monitoring of Community Wastewater Management System Performance for Sustainable Operations.

Community wastewater management systems (CWMS) are small-scale wastewater treatment systems typically in regional and rural areas with less sophisticated treatment processes and often managed by local governments or communities. Research and industrial applications have demonstrated that online UV-Vis sensors have great potential for improving wastewater monitoring and treatment processes. Existing studies on the development of surrogate parameters with models from spectral data for wastewater were largely limited to lab-based. In contrast, industrial applications of these sensors have primarily targeted large wastewater treatment plants (WWTPs), leaving a gap in research for small-scale WWTPs. This paper demonstrates the suitability of using a field-based online UV-Vis sensor combined with advanced data analytics for CWMSs as an early warning for process upset to support sustainable operations. An industry case study is provided to demonstrate the development of surrogate monitoring parameters for total suspended solids (TSSs) and chemical oxygen demand (COD) using the UV-Vis spectral data from an online UV-Vis sensor. Absorbances at a wavelength of 625 nm (UV625) and absorbances at a wavelength of 265 nm (UV265) were identified as surrogate parameters to measure TSSs and COD, respectively. This study contributes to the improvement of WWTP performance with a continuous monitoring system by developing a process monitoring framework and optimization strategy.

When does infrastructure hybridisation outperform centralised infrastructure paradigms? – Exploring economic and hydraulic impacts of decentralised urban wastewater system expansion

We explore the dynamics of centralised and decentralised wastewater infrastructure across various scenarios and introduce novel insights into their performance regarding structural vulnerability, hydraulic capacity, and costs. This study determines circumstances under which infrastructure hybridisation outperforms traditional centralised infrastructure paradigms. We combined system analysis to map out the modelling problem with the model-based exploration of the transition space using the novel TURN-Sewers model. System diagramming was used to identify the parameters or combinations of parameters that significantly influence the performance indicators being assessed. This allowed the creation of relevant simulation scenarios to identify circumstances where a decentralised sewer system could outperform a centralised one. TURN-Sewers was applied to model the infrastructure maintenance and generation of new infrastructure over 20 years for a municipality on the Swiss Plateau, considering a population growth rate of 0.03 a−1. Results show that decentralisation in expansion areas with higher densification can outperform the hydraulic performance and structural vulnerability of expanding centralised sanitary wastewater infrastructure. Decentralised systems can also offer economic advantages when capital expenditure costs for small-scale wastewater treatment plants are significantly reduced compared to current costs, particularly at higher discount rates, e.g. reaping effects of economies of scale. The findings of this study emphasise the potential of transition pathways towards decentralisation in urban water infrastructures and the value of models that allow the exploration of this transition space.

Small Scale Wastewater Treatment Method for Rainwater Garden Based on Photovoltaic Photocatalysis Technology

Conventional small-scale sewage treatment mostly adopts the principle of biological contact oxidation process, which has limited scope of application, low degradation rate of pollutants in sewage, and poor sewage treatment effect. Based on this, a new small-scale sewage treatment method was proposed by introducing photovoltaic photocatalysis technology and taking S sponge community in Ningnan County, Liangshan Prefecture as an example. First, hydrothermal method is used to prepare photocatalyst to provide basic guarantee for sewage treatment. Secondly, the rainwater garden model is simulated and designed to obtain the composition and content of small-scale sewage. On this basis, a rainwater garden photovoltaic photocatalytic water purification system is designed, which establishes an A/O integrated process by connecting the anoxic zone (A section) and aerobic zone (O section) in series to fully achieve the goal of sewage treatment. Experimental analysis shows that the new method can significantly improve the degradation rate of organic pollutants in rainwater garden wastewater, with a degradation rate of over 99% and a maximum degradation time of 10.97 seconds, indicating that the application effect of this method is good.

In-situ sulfite treatment promotes solid reduction during aerobic digestion of waste activated sludge: Feasibility for small-scale wastewater treatment plants

Aerobic digestion remains the preferred choice for small-scale wastewater treatment plants (WWTPs) in some developing countries, largely due to economic viability and operational simplicity. The escalating production of waste activated sludge (WAS) has prompted small-scale WWTPs to improve efficiency. To address this issue, this study employed an in-situ sulfite treatment as a non-intrusive method to augment aerobic digestion. With sulfite-enhanced solubilization and hydrolysis, a 3.6-fold increase in degradation was achieved. Both sludge dewatering properties and pathogens inactivation were improved. Microbial community analysis revealed a preferential enrichment of Actinobacteriota and Firmicutes during sulfite treatment. The desktop scaling-up estimation suggests that implementing this treatment yielded operational cost savings exceeding 40 %. In summary, in-situ sulfite treatment offers a cost-effective strategy for WAS management in small-scale WWTPs.

Life-cycle analysis of environmental loads from household septic systems in Japan focusing on effluent water discharge

Abstract Various types of small-scale wastewater treatment systems are widely used in rural areas, and life-cycle assessment (LCA) should be performed to evaluate their environmental performance. In this study, septic systems were first classified into five categories based on their wastewater treatment performance. Effluent samples from actual systems were collected, and their water qualities were determined. A model to evaluate the environmental load from the septic systems using LCA methods was then established. The water-quality values obtained were input to the model, and the life-cycle environmental costs of the classified septic systems were calculated. The mean environmental load of the effluent during the operation stage was 37.6%, confirming that evaluation of an effluent discharge inventory using LCA, inspection, and water-quality monitoring to improve operations is critical for reducing the environmental load. The operation stage accounts for over 99% of the involved eutrophication, biological toxicity, and toxic chemicals, which are strongly related to the quality of the effluent. Evaluation of the effluent discharge inventory using LCA is of great significance, even for small-scale wastewater treatment systems. The set of procedures developed in this study can be used to calculate comprehensive environmental impacts at wastewater treatment plants.

Socio-Hydrological Approach for Water Resource Management and Human Well-Being in Pinglin District, Taiwan

Despite being a limited resource, pollution, poor management, and other drivers like climate change make available water unsuitable and insufficient for human consumption and ecosystem maintenance. Therefore, a transdisciplinary approach is needed for managing this precious resource. The overall aim of this paper is to address water inequalities and improve human well-being using an integrated approach of key informant interviews, hydrological modeling, and the payment of ecosystem services (PES) scheme in Pinglin District, Taiwan. This site is an upstream area of Feicui Reservoir, which protects the downstream tap water supply. Key informant interviews were conducted to identify the gaps in and challenges to water resource management. This was followed by a scenario-based hydrological simulation using a Water Evaluation and Planning (WEAP) tool to project future water quality by the year 2050 (using biochemical oxygen demand and total coliform content as key indicator parameters) and to trace the factors responsible for water pollution. Survey analysis of key informant interviews depicts that this area is facing several challenges, such as lack of water infrastructure, agricultural subsidy, construction restrictions, etc., which cumulatively cause water scarcity in the upstream regions. On the other hand, hydrological simulation results show that population decline and climate change under an RCP 8.5 scenario will have an enormous negative impact on water quality. The concentrations of BOD and E. coli in river water will expand by 110.1% and 117.3%, respectively, by 2050 compared to 2018. Finally, the results of the study suggest that the PES scheme can play a positive role in enabling integrated water resource management. For example construction of a small-scale wastewater treatment plant in the upstream area will reduce the total E. coli concentration by up to 90%. While the initial cost of construction will be taken care of by the government, the operation and management cost of this infrastructure will be covered by people living downstream, who need to pay only $0.10 per year per person. The obtained results should be vital for both the stakeholders and decision-makers in this region.

Estimating the effect of wastewater treatment facility’s operating failure due to disaster on river’s water quality

The study investigated a disaster countermeasure system for wastewater treatment facilities, focusing on both structural and non-structural responses. As part of the non-structural countermeasures, the effect of untreated effluent from damaged wastewater treatment facilities due to disasters on the river was simulated. The results showed that untreated effluent from the wastewater treatment facility did not affect the river's water quality due to its low flowrate. However, it had a significant impact on the water quality of the river when the flowrate of untreated effluent had increased. The study also evaluated the efficiency of movable treatment units as part of structural countermeasures to respond to damaged wastewater treatment facilities. The researchers simulated the effect of effluent treated by movable treatment units on the river. The findings indicated that movable treatment units were effective in reducing the impact on the river's water quality for small-scale wastewater treatment facilities. However, for mid and large-scale wastewater treatment facilities, disaster countermeasures should prioritize ensuring sufficient storage space for untreated water rather than relying on other emergency response devices, such as movable treatment units tested in this study, to respond to disasters.

Environmental and economic assessment of a floating constructed wetland to rehabilitate eutrophicated waterways

While the reduced carbon footprint of conventional constructed wetlands (CW) for wastewater treatment has been described in the literature, far less information is available on the economic performance of floating filters and their application for the treatment of other pressing environmental problems such as freshwater eutrophication. This investigation describes the technical characteristics and the environmental life cycle assessment (E-LCA) and a life cycle cost (LCC) analysis of a Typha domingensis floating constructed wetland (FCW) designed and constructed to rehabilitate eutrophicated waterways and which also produces biomass for animal feed. The analysis is based on a precise material, energy and economic inventory from a demonstration project built in the Alagón river basin (central Spain). The E-LCA followed a cradle-to-grave approach, used the EF3.0 impact assessment methodology and was referred to two complementary functional units related to the water treatment capacity of the floating filter: 1 m3 of treated water and 1 kg of N fixed, both over a 10-year operating cycle. Climate change emissions were estimated at 0.012 kg CO2 eq./m3, which included 0.082 kg CO2 eq./m3 caused by the construction, operation and decommissioning of the infrastructure, minus 0.070 kg CO2 eq./m3 credits from the production of fodder for animal feed. Considering its nitrogen uptake capacity, this may be represented as 0.845 kg CO2 eq./kg N. Most of this carbon footprint comes from the construction (63.2 %) and the operation (31.1 %) stages, with the former being dominated by auxiliary materials (mainly plastics and cereal straw) needed to build the infrastructure and the energy system (mainly PV panels). This same pattern is replicated in most other environmental categories and the aggregated single score. Further research is needed to quantify with precision direct CH4 and N2O emissions produced during the operation stage, whose contribution can be significant (up to 64.8 % over indirect LCA emissions). The LCC analysis resulted in discounted expenses over the 10-year cycle of 44,083 € and revenues derived from the sale of fodder for animal feed of 11,429 €, resulting in a net present value of 32,654 €. These expenses may be represented as 0.302 €/m3 of treated water (or 21.1 €/kg of N fixed). The monetary cost and environmental footprint per functional unit of floating CW are lower than those reported for other conventional small-scale wastewater treatment technologies.

Ensemble machine learning approach for examining critical process parameters and scale-up opportunities of microbial electrochemical systems for hydrogen peroxide production

Hydrogen peroxide (H2O2) production in microbial electrochemical systems (MESs) is an attractive option for enabling a circular economy in the water/wastewater sector. Here, a machine learning algorithm was developed, using a meta-learning approach, to predict the H2O2 production rates in MES based on the seven input variables, including various design and operating parameters. The developed models were trained and cross-validated using the experimental data collected from 25 published reports. The final ensemble meta-learner model (combining 60 models) demonstrated a high prediction accuracy with very high R2 (0.983) and low root-mean-square error (RMSE) (0.647 kg H2O2 m−3 d−1) values. The model identified the carbon felt anode, GDE cathode, and cathode-to-anode volume ratio as the top three most important input features. Further scale-up analysis for small-scale wastewater treatment plants indicated that proper design and operating conditions could increase the H2O2 production rate to as high as 9 kg m−3 d−1.

Artificial Intelligence-Assisted Prediction of Effluent Phosphorus in a Full-Scale Wastewater Treatment Plant with Missing Phosphorus Input and Removal Data

Although artificial intelligence (AI) such as machine learning (ML) and deep learning (DL) has been recognized as an emerging and promising tool, its application becomes challenging with incomplete data collection. Herein, in the absence of the influent phosphorus load and chemical dosage data for phosphorus removal, we employed ML/DL models to predict effluent phosphorus using nine-year data from a small-scale wastewater treatment plant. Attempts were made to select essential model input features from 42 variables by using Pearson correlation analysis to reveal internal correlations among variables. First, five ML regression models were used to predict the effluent phosphorus load, and a maximum coefficient of determination (R2) of 0.637 was achieved with the support vector machine model. Then, the DL model named long short-term memory could predict phosphorus load in one-day advance with an R2 value of 0.496. Finally, on the basis of the historical data, an anomaly alarm design was proposed to minimize the chance of exceeding the discharge permit and achieved a maximum accuracy of 79.7% to predict the phosphorus concentration after comparing seven ML classification models. This study provides an example of applying AI for process improvement and potential cost reduction with incomplete data sets.

Assessment in treatment efficiency of a small-scale municipal wastewater treatment plant with activated sludge

Abstract In this paper, the treatment efficiency of a small-scale wastewater treatment plant (WWTP) with activated sludge was analysed in order to examine the impact of variations in the composition of incoming raw municipal wastewater. The characteristics of the wastewater were analysed with respect to COD, BOD5 and TSS values and loading during the two years, 2018 and 2019. The mixed liquid suspended solid (MLSS), sludge volume index (SVI), food to microorganism ratio (F/M), sludge age and hydraulic retention time (HRT) were used for evaluation of the performance of WWTP. Removal percentage is in the order of TSS > BOD5 > COD during 2018, while in 2019 is in the order BOD5 > TSS > COD. However, better values of removal efficiency for COD, BOD and TSS are obtained in 2019, which is connected to lower oscillation values of MLSS and SVI index. Biodegradability ratio of raw and treated wastewater, plant reliability factor (RF) and equivalent number of inhabitant (ENI) were determined. In addition, the economic cost of small-scale wastewater treatment plant (WWTP) with activated sludge was evaluated and discussed.

Biological treatment of municipal wastewater using fixed rope media technology: Impact of aeration scheme

This paper characterized a new fixed rope media system to upgrade decentralized and small-scale wastewater treatment plants. A primary effluent of municipal wastewater was treated using two pilot-scale reactors equipped with full-scale sized fixed rope media technology, one of the reactors was aerated using a coarse bubble tube and the other using a custom fine bubble aeration system. The study examined the impact of the aeration scheme and intensities and the COD/NH 3 -N ratio on ammonia and COD removal rates, excessive biofilm growth, slough-off, and microbial communities’ composition. The average biofilm ammonia and COD removal rates ranged from 0.23 ± 0.15 to 0.38 ± 0.26 gNH 3 -N/m 2 .d and 1.35 ± 0.95 to 3.05 ± 1.21 gCOD/m 2 .d, respectively. The fine and coarse bubble reactors showed comparable carbon oxidation rates; however, the fine bubble reactor showed a higher nitrification rate than the coarse bubble reactor at lower aeration intensities despite the similar dissolved oxygen concentration. Correspondingly, an increase in COD/NH 3 -N and excessive biofilm growth decreased the NH 3 -N removal performance but did not affect the COD removal efficiency. Further analysis of the microbial communities composition revealed that the reactors supported a relatively substantial amount of AOB (55 and 63%) and denitrifying bacteria (36 and 21%) with a relatively lower NOB (7 and 8%) and anammox (1 and 8%) species in the fine and coarse bubble aeration reactors, respectively. Overall this study demonstrated the feasibility of one stage fixed rope media to treat COD and ammonia and meet treatment objectives, thus providing an alternative solution to decentralized and smaller plant upgrades. • Ammonia and COD removal efficiency of innovative fixed rope media technology was evaluated. • Different aeration schemes showed minimal impact on the DO concentration but impacted removal performances. • C/N ratio influenced NH 3 -N removal but not COD removal. • Slough off did not impact COD removal; however, it enhanced ammonia removal. • Reactor with the fine bubble aeration supported a relatively higher fraction of denitrifying bacteria.

Design of 50KLD Sewage Treatment Plant

Abstract: Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage. Canteen of every academic organization need a lot of clean water, and it generates equivalent amount of wastewater every hour which is neither purified nor reused. Due to water scarcity, the recycling and reusing of wastewater become very essential. The present study describes the simple and Cost-effective method for the design of a smallscale wastewater treatment plant for the purification of wastewater generated by canteen of Ma’din College. The present study involves the Analysis of pH value, total solid , total Suspension solid , hardness,Acidity , oil fat and grease , chloride ,BOD,DO etc. The Sampling of the waste water have been done in different times of the day to have an Average data of measure parameters.

Intermittent Microaeration Technology to Enhance the Carbon Source Release of Particulate Organic Matter in Domestic Sewage

Domestic sewage treatment plants often have insufficient carbon sources in the influent water. To solve this problem, the commonly used technical means include an additional carbon source, primary sludge fermentation, and excess sludge fermentation, but these methods are uneconomical, unsustainable, and not applicable to small-scale wastewater treatment plants. Intermittent microaeration technology has the advantages of low energy-consumption, ease of application, and low cost, and can effectively promote anaerobic digestion of municipal sludge; however little research has been reported on its use to enhance the carbon sources release of particulate organic matter (POM) from domestic wastewater. Therefore, the effect of intermittent microaeration on the carbon source release of POM was evaluated in this study, with POM as the control test. The results showed that the release concentration of soluble chemical oxygen demand (SCOD) was the highest on day 4 under microaerobic conditions, and the concentrations of SCOD, NH4+-N, and PO43−-P in the liquid phase were 1153, 137.1, and 13 mg/L, respectively. Compared with the control group, the SCOD concentration increased by 34.2%, and the NH4+-N and PO43−-P concentrations decreased by 18.65% and 17.09%, respectively. Intermittent microaeration can effectively promote the growth of Paludibacter, Actinomyces, and Trichococcus hydrolytic fermentation functional bacteria. Their relative abundances increased by 282.83%, 21.77%, and 23.47%, respectively, compared with the control group. It can simultaneously inhibit the growth of acetate-type methanogenic archaea, Methanosaeta and Methanosarcina, with a decrease in relative abundances of 16.81% and 6.63%, respectively. The aforementioned data show that intermittent microaeration can not only promote the hydrolysis of POM, but can also reduce the loss of acetic acid carbon source, which is a cost-effective technical way to enhance the release of a carbon source of particulate organic matter in domestic sewage.

Improving the efficiency of small-scale wastewater treatment by pneumatic agitation

Small-scale anaerobic and aerobic systems for wastewater treatment suffer relatively low efficiencies due primarily to a lack of mechanical agitation/mixing. Here, a pneumatic agitation system was designed by installing a U-tube between the anaerobic and anoxic units, pumping air to the closed headspace of the anaerobic unit and releasing the pressurized air through the U-tube to create turbulence of the fluid. Computational Fluid Dynamics (CFD) simulation and fluid tracer trial were used to describe the fluid status in a lab-scale system (13 L). The results demonstrated that a continuous 5-cycle pneumatic agitation achieved a complete mixing of the static fluid. The retention time factor ( β ) and short-circuiting flow coefficient ( t i /HRT) were increased from 0.93 to 1.14 and 0.02 to 0.27, respectively, indicating that pneumatic agitation significantly reduced dead zone and short-circuiting flow. A prototype at a treatment capacity of 300 L/d was installed in the North-East suburb of Beijing (40.15° N, 116.95° E) to treat rural household wastewater consisting of 630–1200 mg/L chemical oxygen demand and 20–45 mg/L total nitrogen. The field test was monitored in a period of 75 days from September to November 2018. The average removal rate for COD and TN was 96% and 92%, respectively by 10 times/h pneumatic agitation as compared to 49% and 45% without pneumatic agitation. The pneumatic agitation provides a low cost, easy operation and maintenance and efficient means for small-scale domestic wastewater treatment. • Pneumatic agitation improved the performance of small-scale wastewater treatment. • CFD simulation was applied to describe the process of the pneumatic agitation. • Fluid tracer trials were employed to analyze the hydraulic characteristics. • A prototype of 300 L/d was installed on-site to treat a rural household wastewater.

Occurrence of E. coli and antibiotic-resistant E. coli in the southern watershed of Lake Biwa, including in wastewater treatment plant effluent and inflow rivers

The emergence of antibiotic-resistant bacteria (ARB) and their antibiotic resistance genes (ARGs) poses a serious challenge to human, animal, and environmental health worldwide. ARB can spread into the environment via various sources and routes. In this study, we investigated the occurrence of antibiotic-resistant E. coli in the southern watershed of Lake Biwa. Two-year monitoring of antibiotic-resistant E. coli was carried out in the southern part of Lake Biwa and inflow rivers and at three WWTPs around the southern part of the lake. Concentrations of E. coli in waters that are resistant to ampicillin (AMP), cefotaxime (CTX), ceftazidime (CAZ), levofloxacin (LVFX), tetracycline (TC), and amikacin (AMK) were measured using the culture method. Of these antibiotic-resistant E. coli, AMP-resistant E. coli were found at the highest prevalence, followed by LVFX, CTX, CAZ, TC, and AMK-resistant in both the influent and effluent of WWTPs. These resistance patterns in wastewater are the same as those in clinical samples in Japan. The numbers of antibiotic-resistant E. coli decreased by around a factor of 1000 during the wastewater treatment processes, but the rates clearly increased, suggesting that selection for antibiotic resistance might occur during the wastewater treatment process. AMP-resistant and TC-resistant E. coli were also detected in Lake Biwa and inflow rivers, which suggests that antibiotic resistance might come from not only WWTPs but also livestock farms and small-scale wastewater treatment facilities located in the river catchment.

Quantification and qualification of the urban domestic pollution discharged per household and per resident.

The research study aims to analyze the discharges of solely domestic wastewater from 15 single-family dwellings. This sizable dataset, containing over 300 unique and insightful data points, makes it possible to accurately qualify the raw wastewater in terms of concentrations, volumes and pollutant loads. Findings quantify the extremely wide data variability. As such, for single-family households of fewer than six residents, it is suggested not to use the standard P.E. pollution value as the design load, but rather a load range defined by the interval [10th percentile, 90th percentile] of the data distribution, i.e. [123; 568 L·d- 1] and [30; 281 g BOD5·d-1], respectively, for the daily hydraulic and organic loads. Also, an analysis of the hydraulic peak factor would tend to lobby in favor of a collective sewer solution. For subdivisions and residential zones with little economic activity and similar French lifestyle, the daily domestic pollution per resident is now determined with the values: 40 g suspended solids, 94 g carbon oxygen demand, 40 g five-day biochemical oxygen demand, 6.7 g NH4+-N, 10.4 g Kjeldhal nitrogen, and 1.2 g total phosphorus for a volume of 83 L. Those data could be used to optimize design and operation of decentralized or small-scale wastewater treatment plant.

Performance of a post-nitrification process with carriers for residual ammonia nitrogen removal in secondary effluent, aimed at small-scale wastewater treatment plants

Performance of a post-nitrification process with carriers for residual ammonia nitrogen removal in secondary effluent, aimed at small-scale wastewater treatment plants

The purification of wastewater on a small scale by using plants and sand filter

The canteen and laboratory of every academic organization need a lot of clean water, and it generates equivalent amount of wastewater every hour which is neither purified nor reused. Due to water scarcity, the recycling and reusing of wastewater become very essential. The present study describes the simple and cost-effective method for the design of a small-scale wastewater treatment plant for the purification of wastewater generated by household, canteen and laboratory of an academic institute. The current study explored the process of phytoremediation by Typha latifolia L. and Canna indica L. for removal of metal ions and phosphate ions from the wastewater. The partially treated water after phytoremediation was further purified by sand filtration. The various water quality parameters (pH, hardness, dissolved oxygen, chemical oxygen demand, turbidity, total dissolved solids and metal ions) of the treated and untreated water were analyzed. It was observed that there are significant reduction in hardness, turbidity and chemical oxygen demand and increase in dissolved oxygen value. The treated water can be reused for various household works and agriculture.

Portable wastewater treatment plant using banana stem filter media in small scale motor vehicle washing services

One of the technology that can be applied to small-scale wastewater treatment was used simple filtering system. In general, water filter media uses a mixture with layered system such as silica sand media, zeolite, manganese green sand, and activated carbon. Portable WWTP can be used for effective and efficient motorized vehicle washing wastewater treatment so that the wastewater was environmentally friendly and can be reused. The variables used in the design test are TSS, Detergent and pH. Filter media that used were banana stem, zeolite sand and activated carbon with a thickness of 50 cm, a downflow-upflow flow and a duration of 3 days. The results showed that the average percentage of effectiveness after going through IPAL were 31% BP-BP (banana stem-banana stem), 46% BP-PK (banana stem-sand carbon), and PZ-KA (zeolite-activated carbon) by 48%. The use of banana stem filters was considered more economical, easy to obtain, fast, lightweight and practise. Banana stem filter media was also more effective in lowering pH. The use of variety banana stem filter media with a combination sand and carbon (BP-PK) can minimize the weakness of the sand filter, which generally requires a long flow time and sufficient pressure.