Production Of High-quality Water Research Articles

Membrane fouling control and contaminant removal during direct nanofiltration of surface water

Direct nanofiltration (NF) is an attractive separation process that produces high-quality drinking water without pretreatment. However, the propensity for membrane fouling is a considerable challenge. This study evaluated the potential of direct NF treatment of surface water using submerged flat-sheet (polyamide composite) NF membranes to achieve stable operation and high-quality water production. Direct NF treatment at a constant permeate flux of 5.0 L/m2h (NF270) and 2.5 L/m2h (NF90) was successfully continued for over 100 d with a monthly one-wipe sponge cleaning. Sponge cleaning eliminated the foulants on the NF270 membrane surface, thereby recovering the membrane permeability. Contrastingly, tight NF90 membranes did not exhibit significant changes in membrane permeability. The rejection of odorous compounds and other dissolved organic matter by the NF90 membrane was significant (>95 %), whereas those by the NF270 membrane considerably varied with the feed temperature. Further investigation suggested that the visible foulant on the membrane surface could be a porous cake layer mainly composed of constituents with a molecular weight of >300 Da, resulting in low hydraulic resistance. One-wipe sponge cleaning can readily detach fluffy cake layers. The results of this study suggest the viability of direct NF treatment as a low-energy advanced drinking water treatment system.

Performance of a novel granular activated carbon and gravity-driven membrane hybrid process: Process development and removal of emerging contaminants

In this study, a novel granular activated carbon (GAC) gravity-driven membrane (GDM) hybrid system with a ceramic membrane was developed for the production of high quality water. The operational performance in water permeability; removal of organic matter; and contaminants of emerging concern (CECs) including microplastics, larvae, and perfluorinated compounds (i.e., perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid(PFOS)) was evaluated. The experimental results indicate that the GAC-GDM hybrid system can overcome the limitations of the GAC (i.e., low rejection efficiency of particulates) and GDM (i.e., low rejection efficiency of organics) processes. The GDM process showed higher removal rates of microplastics and larvae than the GAC process (i.e., 77.9% and 100% vs. 16.6% and 70%, respectively), and the GAC process exhibited higher removal rates of organic matter and perfluorinated compounds (PFOA and PFOS) than the GDM process (i.e., 54.8%, 90.9% and 99.1% vs. 17.6%, 23% and 31.8%, respectively). In the GAC-GDM hybrid system, stable water flux was observed with the efficient removal of CECs and organic matter during operation. This study implies that the GAC-GDM system can be used as a distributed water treatment system in remote areas such as islands and mountains because the GAC-GDM system is able to minimize the operation scale.

Precise separation of small neutral solutes with mixed-diamine-based nanofiltration membranes and the impact of solvent activation

Mixed-diamine-based nanofilm composite membranes prepared with 1.0 wt% PIP and 0.1 wt% MPD on crosslinked polyimide (XP84) UF support show a seven times higher selectivity of ∼ 59.0 between glycerol and glucose than the conventional membranes (selectivity of ∼ 8.2). Membranes also show a ∼ 55.8% increase in pure water permeance (PWP) without altering Na 2 SO 4 rejection (from 99.27 % to 99.53%) and an increased selectivity between NaCl to Na 2 SO 4 (from 43.7 to 98.9) after solvent activation with DMF. Additionally, after solvent activation, mixed-diamine-based nanofilm composite membranes show a sharp and reduced molecular weight cut-off (MWCO) compared to the membranes prepared from semi-aromatic polyamide. • 1. Nanofilm membranes are made from mixed diamines via interfacial polymerization. • 2. Nanofilm membranes show a seven times higher selectivity between glycerol and glucose. • 3. Membranes show a ∼ 55.8% increase in pure water permeance upon DMF activation. • 4. Nanofilm membranes show a sharp and reduced MWCO (∼170 Da) upon DMF activation. • 5. The mean pore size is ∼ 13.0 Å with an enhancement of up to 22.6% after DMF activation. High permeance membranes selective towards small ions and solutes are required to produce high-quality product water. Conventional semi-aromatic polyamide thin-film composite (TFC) nanofiltration membranes prepared via interfacial polymerization of diamine, e.g., piperazine (PIP) and acid chloride, do not show the precise separation of small solutes (<200 Da). To achieve this, we introduced an aromatic diamine group, e.g., m -phenylenediamine (MPD), within the semi-aromatic polyamide structure to achieve selective separation between small solutes with enhanced permeation upon solvent activation. Herein, we report the fabrication of polyamide nanofilm composite membranes using a mixture of PIP and MPD as a diamine precursor and react with trimesoyl chloride (TMC) on top of the ultrafiltration (UF) supports. Nanofilm composite membranes prepared with 1.0 wt% PIP and 0.1 wt% MPD on crosslinked polyimide (XP84) UF support show a seven times higher selectivity of ∼ 59.0 between glycerol and glucose than the conventional nanofiltration membranes (selectivity of ∼ 8.2). Membranes also show a ∼ 55.8% increase in pure water permeance (PWP) with identical Na 2 SO 4 rejection (99.27% – 99.53%) and an increased selectivity between NaCl to Na 2 SO 4 (from 43.7 to 98.9) after solvent activation with DMF. Additionally, after solvent activation, mixed-diamine-based nanofilm composite membranes show a sharp and reduced molecular weight cut-off (MWCO ∼ 170 Da) compared to the nanofiltration membranes prepared from semi-aromatic polyamide. The permeation results conducted with small neutral solutes in the aqueous feed suggest the existence of pores of mean size ∼ 13.0 Å, with an enhancement of pore sizes ∼ 7 – 22.6% after DMF activation. The process of membrane fabrication is acceptable for large-scale manufacturing.

Enzyme-aided forward osmosis (E-FO) process to enhance removal of micropollutants from water resources

Membrane filtration has proven its advantages in removing micropollutants from water. However, concentrated micropollutants in feed solutions still pose a high risk to environments and may contaminate the permeate. Here, a proof-of-concept of enzyme-aided forward osmosis (E-FO) process was demonstrated. In E-FO process, degradation and rejection of micropollutants occurred simultaneously, providing a detoxified feed solution and a cleaner permeate. A lab-made polyketone-based thin film composite membrane with high flux and high micropollutants rejection was explored as FO membrane. Laccase and 2, 4, 6-trichlorophenol (TCP) was employed as a model enzyme and micropollutant, respectively. Compared with a single enzyme catalysis, E-FO process showed a higher degradation efficiency owing to enzyme condensation during filtration. Compared with a single FO process including 0.051 mM TCP in feed solution, E-FO process adding 0.8 μM laccase showed 7.4 and 10.7 times lower TCP permeation and membrane adsorption when operated for 10 h. An enzyme-aided reverse osmosis (E-RO) process can produce clean water with similar quality as that of E-FO, however, suffers from membrane fouling. This work provides an insight in facile coupling of efficient enzyme catalysis with low fouling FO process for high quality water production from contaminated water resources.

Effect of sintering temperature of bauxite hollow fiber membrane on flexural strength and water permeability

With abundant Malaysian bauxite minerals as the selected materials, hollow fiber ceramic membrane was fabricated for efficient production of high quality water from oil field oily wastewater. Effect of sintering temperature between 1250°C and 1450°C on membrane porosity, size of membrane pore, hydrophilicity, mechanical strength and water permeation were examined and the results were analyzed to determine the most suitable hollow fiber membrane for the application. Based on obtained findings, the most suitable sintering temperature was 1350°C. The acceptable strength and morphological behavior of finger-like and sponge-like voids were found to be advantageous characteristics for the fabricated bauxite hollow fiber membrane. Its pleasant structure with good outer and inner layers of separation might be beneficial for the oily wastewater purification applications.

Process simulation of ion exchange desalination treatment of coal seam gas associated water

The aim of this investigation was to develop an ion exchange process for the remediation of coal seam gas (CSG) associated water to make it suitable for beneficial reuse. The hypothesis was that computational modelling could accelerate the selection of appropriate ion exchange desalination strategies. Hence, we applied AqMB water process engineering software to predict which combination of weak acid cation (WAC), strong acid cation (SAC), weak base anion (WBA) and strong base anion (SBA) resins were most appropriate. Simulation results revealed that both SAC/WBA and SAC/SBA resin combinations were unable to meet water beneficial reuse standards for conductivity (< 950 μS/cm) due to the presence of bicarbonate species (4973 and 1918 μS/cm, respectively). Thus, a degasser unit was necessary to remove the large concentrations (ca. 1328 mg/L) of dissolved carbon dioxide formed due to decomposition of bicarbonate/carbonate species under acidic conditions in the cation resin stages. pH adjustment of effluent from the preferred SBA resin with acid not only did not meet solution conductivity guidelines but also raised the concentration of chloride or sulphate ions to levels, which may be detrimental for crop growth. Addition of a WAC resin allowed production of high quality water (either SAC/SBA/WAC or WAC/SAC/SBA combinations). To comply with sodium adsorption ratio requirements for irrigating soil it was suggested to apply micronized gypsum to the treated water. Economic evaluation suggested the treated water cost was A$1003 (WAC/SAC/SBA) to A$1276 (SAC/SBA/WAC) per ML treated which was comparable to estimated costs for a reverse osmosis desalination system.

Integration of MBR with NF/RO processes for industrial wastewater reclamation and water reuse-effect of membrane type on product water quality

In this study, some field tests were conducted at ITOB Organized Industrial Zone Wastewater Treatment Plant where membrane bioreactor (MBR) process has been used for wastewater treatment. The MBR treatment process provides stable and high quality product water but product water still contains high salinity in this case. Therefore, a mini-pilot scale membrane test system having three different nanofiltration (NF) which are NF90, NF270 and TR60 and two different reverse osmosis (RO) membranes which are BW30 and AG with spiral wound configurations was employed for demineralization of MBR effluent. The system was operated with 10 bar of operating pressure for NF membranes and at 20 bar for RO membranes. The average water recoveries of NF membranes were 50.2%, 56.0% and 51.8% for NF90, NF270 and TR60 membranes, respectively while average water recoveries of RO membranes were 64.0% for BW30 membrane and 62.3% for AG membrane. The qualities of product waters were analyzed and compared with standards to reuse them for agricultural irrigation and as process water. The permeates of NF270 and TR60 membranes agreed well with the third class water quality for salinity and the second class quality for the rest of parameters. On the other hand, the permeates of NF90, BW30 and AG membranes provided with the first class water for all parameters except for infiltration. Mixing the permeates of NF and RO membranes with MBR effluent in appropriate ratios was considered to be helpful to get acceptable quality values for product water and a good permeability for agricultural irrigation. Therefore, an optimum theoretical mixture of MBR effluent to permeates was determined. When qualities of product water obtained by NF and RO membranes were compared with the standards of cooling and boiling feedwaters for industrial usage and with the process water characteristics for pulp and paper, textile industries, it was considered that the permeates of NF90, BW30 and AG membranes obeyed well the quality standards required.

Integrating an aerobic/anoxic osmotic membrane bioreactor with membrane distillation for potable reuse

A novel osmotic membrane bioreactor-membrane distillation (OMBR-MD) system was designed and fabricated to treat wastewater for potable reuse. Before longer-term operation to evaluate water flux and biological treatment of the pilot-scale OMBR subsystem, two forward osmosis (FO) membranes were evaluated at the bench-scale. There was no statistical difference between cellulose triacetate and thin-film composite membrane performance for activated sludge feed solution. Also, FO water flux during long-term operation was the same for 20 and 35g/L NaCl draw solutions; however, the 35g/L NaCl draw solution resulted in greater reverse salt flux and higher conductivity in the bioreactor. The OMBR subsystem was integrated with an MD subsystem to reconcentrate the draw solution and produce high quality product water. Results from long-term testing using a high-strength wastewater showed 98.4% COD removal and 90.2% NH4+-N could be achieved with a single bioreactor by alternating aeration on/off cycles to control the redox environment. An automated dosing and transfer system was developed to maintain constant FO draw solution concentration and prevent heat from being transferred to the bioreactor, which is critical for maintaining biological nitrogen removal.

Application of the CANARY event detection software for real-time performance monitoring of decentralized water reuse systems.

Real-time monitoring of water reuse systems ensures the production of high quality water to protect human health at the point-of-use. In this study, several online real-time sensors were utilized to monitor effluent from a wastewater fed laboratory-scale membrane bioreactor (MBR) under natural and simulated failure conditions. These simulated failures included adding reactor mixed liquor to emulate a membrane breach, and spiking MS2 bacteriophage into the reactor to create a high viral load, which might be observed during an outbreak. The CANARY event detection software was used to analyze sensor data and report changes in water quality that might be indicative of poor system behavior. During simulated failure conditions, CANARY reported 20 alarms, accurately detecting each failure. During natural operating conditions, 219 alarms were produced and 189 were attributed to known events (e.g., system and sensor maintenance). The remaining alarms (23) during natural operating conditions were considered to have an unknown cause. However, 13 of those had signal deviations similar to known events, but could not be definitively linked to a source. The results of this study suggest that real-time monitoring in conjunction with CANARY analysis may be useful as an early warning system for monitoring the effluent of water reuse systems, and may help to quickly identify treatment malfunctions or other abnormal conditions.

Membrane distillation for wastewater reverse osmosis concentrate treatment with water reuse potential

Membrane distillation (MD) was evaluated as a treatment option of wastewater reverse osmosis concentrate (WWROC) discharged from wastewater reclamation plants (WRPs). A direct contact MD (DCMD), at obtaining 85% water recovery of WWROC showed only 13–15% flux decline and produced good quality permeate (10–15µS/cm, 99% ion rejection) at moderate feed temperature of 55°C. Prevalent calcium carbonate (CaCO3) deposition on the MD membrane occurred in treating WWROC at elevated concentrations. The combination of low salinity and loose CaCO3 adhesion on the membrane did not significantly contribute to DCMD flux decline. Meanwhile, high organic content in WWROC (58–60mg/L) resulted in a significant membrane hydrophobicity reduction (70% lower water contact angle than virgin membrane) attributed to low molecular weight organic adhesion onto the MD membrane. Granular activated carbon (GAC) pretreatment helped in reducing organic contents of WWROC by 46–50%, and adsorbed a range of hydrophobic and hydrophilic micropollutants. This ensured high quality water production by MD (micropollutants-free) and enhanced its reuse potential. The MD concentrated WWROC was suitable for selective ion precipitation, promising a near zero liquid discharge in WRPs.

Application of liquid desiccant dehumidification to amine-based carbon capture systems

Liquid desiccant-based dehumidification with water recovery is an effective and robust method to remove excess moisture from process gas streams and recover relatively high quality product water. A study was undertaken to determine if desiccant-based technology could be applied to the benefit of an amine-based CO2 capture system since the addition of CO2 capture to a coal-fired power plant can significantly increase the plant’s consumptive water use. Test data with a pilot flue gas moisture recovery system are presented to illustrate the characteristics of the process, including the water recovery potential, product water quality, and thermal energy consumption. The process is then evaluated theoretically under conditions typical of a monoethanolamine-based CO2 capture process. The analysis indicates that there is less opportunity for moisture recovery compared to a plant without CO2 capture because of the cooler processing temperatures associated with CO2 absorption and stripping. However, a desiccant-based dehumidification system might be useful as a heat-driven moisture management tool since desiccant-based moisture removal is more effective than dew point cooling for a given heat rejection temperature. Dehumidifying the CO2 product stream prior to compression might offer incremental power consumption savings compared to other options of moisture vapor management.

Integration of forward osmosis and membrane distillation for sustainable wastewater reuse

Abstract This study focuses on the performance of an integrated forward osmosis (FO) and membrane distillation (MD) process for wastewater reuse. FO worked as a pretreatment barrier to remove most contaminants in the feed water and MD was used to recover the draw solutes from FO effluent and simultaneously produce high-quality reusable water. A unique three-channel FO–MD membrane module was designed and built to test water flux and contaminant removal in bench-scale experiments. It was found that the integrated FO–MD system possessed inherent flux balancing mechanism that enabled a stable and equal water flux for both FO and MD membranes for effective recovery of draw solution over long-term experiments. The FO–MD system was able to achieve more than 3 logs (>99.9%) removal of ammonium, COD, arsenic, and combined solutes in both synthetic and real wastewaters. Such a synergistic integration of FO and MD membrane processes offers three major advantages. First, the upstream FO process removes most contaminants and foulants from the feed solution, thus potentially diminishing the fouling and wetting problem for the downstream MD process. Second, the downstream MD process successfully recovers the draw solution for the FO process, enabling a constant water flux for FO. Third, the synergistic removal capability of FO and MD enabled the production of extremely high-quality product water. Additional benefits of the integrated process include ambient pressure operation and potential use of renewable low-grade heat as the energy source.

ChemInform Abstract: Membrane Distillation Bioreactor (MDBR) ‐ A Lower Green‐House‐Gas (GHG) Option for Industrial Wastewater Reclamation

AbstractReview: 132 refs.

Denitrification of groundwater using a sulfur-oxidizing autotrophic denitrifying anaerobic fluidized-bed MBR: performance and bacterial community structure.

This paper investigates a novel sulfur-oxidizing autotrophic denitrifying anaerobic fluidized bed membrane bioreactor (AnFB-MBR) that has the potential to overcome the limitations of conventional sulfur-oxidizing autotrophic denitrification systems. The AnFB-MBR produced consistent high-quality product water when fed by a synthetic groundwater with NO3 (-)-N ranging 25-80 mg/L and operated at hydraulic retention times of 0.5-5.0 h. A nitrate removal rate of up to 4.0 g NO3 (-)-N/Lreactord was attained by the bioreactor, which exceeded any reported removal capacity. The flux of AnFB-MBR was maintained in the range of 1.5-15 L m(-2) h(-1). Successful membrane cleaning was practiced with cleaning cycles of 35-81 days, which had no obvious effect on the AnFB-MBR performance. The (15) N-tracer analyses elucidated that nitrogen was converted into (15) N2-N and (15) N-biomass accounting for 88.1-93.1 % and 6.4-11.6 % of the total nitrogen produced, respectively. Only 0.3-0.5 % of removed nitrogen was in form of (15)N2O-N in sulfur-oxidizing autotrophic denitrification process, reducing potential risks of a significant amount of N2O emissions. The sulfur-oxidizing autotrophic denitrifying bacterial consortium was composed mainly of bacteria from Proteobacteria, Chlorobi, and Chloroflexi phyla, with genera Thiobacillus, Sulfurimonas, and Ignavibacteriales dominating the consortium. The pyrosequencing assays also suggested that the stable microbial communities corresponded to the elevated performance of the AnFB-MBR. Overall, this research described relatively high nitrate removal, acceptable flux, indicating future potential for the technology in practice.

Application of membrane distillation technology in the treatment of table olive wastewaters for phenolic compounds concentration and high quality water production

Direct contact membrane distillation process (DCMD) is proposed for the treatment of table olive wastewaters (TOW) for high quality water production and concentration of their phenolic compounds. The main objective was to investigate the effectiveness of DCMD process to concentrate phenolic compounds from TOW that can be reused as a potential source for powerful natural antioxidants. The performance of three commercial membranes, made from polytetrafluoroethylene supported by polypropylene net (TF200, TF450 and TF1000), were tested. The permeate fluxes and polyphenols concentration in both the permeate and retentate have been monitored under different DCMD operating temperatures. It was found that the three membranes exhibit an excellent separation coefficient (greater than 99.5%) even after 4h of DCMD operation with TOW. High concentration factors were obtained with the membrane TF450 at 70°C, while the membrane TF200 having the lowest pore size was found to be more resistant to fouling phenomenon compared to the other membranes since the reduction of its water permeate flux after TOW treatment did not exceed 2.9%. High quality of the permeate was obtained with phenolic concentration lower than 16mg of TYE/L. In addition, the values of electrical conductivity of the permeate were lower than 193μS/cm for the membranes TF450 and TF200, and lower than 355μs/cm for the membrane TF1000. Consequently, DCMD proved to be an effective process for the treatment of TOW for high quality water production and a phenolic-rich concentrate.

Membrane Distillation Bioreactor (MDBR) – A lower Green-House-Gas (GHG) option for industrial wastewater reclamation

A high-retention membrane bioreactor system, the Membrane Distillation Bioreactor (MDBR) is a wastewater reclamation process which has the potential to tap on waste heat generated in industries to produce high quality product water. There are a few key factors which could make MDBR an attractive advanced treatment option, namely tightening legal requirements due to increasing concerns on the micropollutants in industrial wastewater effluents as well as concerns over the electrical requirement of pressurized advanced treatment processes and greenhouse gas emissions associated with wastewater reclamation. This paper aims to provide a consolidated review on the current state of research for the MDBR system and to evaluate the system as a possible lower Green House Gas (GHG) emission option for wastewater reclamation using the membrane bioreactor–reverse osmosis (MBR–RO) system as a baseline for comparison. The areas for potential applications and possible configurations for MDBR applications are discussed.

Production of high-quality water by reverse osmosis of milk dairy condensates

Low-pollution flash cooler (FC) condensates from the direct heat treatment of milk and milk-based products were treated by means of reverse osmosis (RO) in order to obtain high-quality water for use in boilers. The behaviour of the spiral-wound membranes at the pilot-plant scale (8.2m2 surface area) was tested in terms of the permeate flow rate (J) and quality (conductivity and chemical oxygen demand (COD)) as a function of the operation conditions, including the pressure, temperature and volume concentration rate (VCR). Response surfaces were drawn with the aim of obtaining information regarding the permeate flow rate as well as conductivity and COD reduction in the range of the studied parameters. Based on the experimental data, a plant with a 90% recovery rate (RR) was proposed with the objective of carrying out a preliminary economic assessment, which yielded a payback of 1.16 years.

A feasibility study on UV pretreatment for microfiltration and reverse osmosis membrane processes in wastewater reclamation

Wastewater reclamation is where wastewater from various sources is purified so the water can be used by human consumption. Among many treatment options, membranes have gained an important place in wastewater reclamation. It allows the production of high quality water from wastewater, with a small footprint and affordable energy consumption. Nevertheless, membrane fouling is regarded as a serious problem due to the high fouling potential of wastewater. In this study, we applied ultraviolet (UV) processes as a pretreatment for membrane systems that are used for wastewater reclamation. Low pressure UV (LUV) and pulsed UV (PUV) were used to decompose or alter the organics in the feed water of the membranes. Effluent organic matter was characterized by total organic carbon (TOC) and UV absorbance (UVA). Also the effect of UV pretreatment on membrane fouling was investigated for microfiltration (MF) and reverse osmosis (RO) processes. The pretreatment of membranes using LUV or PUV was effective to control fouling of hollow fiber MF membranes. This is probably because of the reduction and modification of organics after UV treatments. However, the effect of UV pretreatment on RO flux was less significant, which is attributed to low fouling prophecy after MF treatment.

Evaluating Membrane Bioreactor Performance When Used with RO for Water Reclamation in Singapore

A large pilot study was conducted in Singapore to evaluate the performance of membrane bioreactors (MBRs) when used with reverse osmosis (RO), particularly focusing on energy consumption. MBRs using microfiltration (MF) membranes made from polyvinylidene difluoride were set up with anoxic, aeration, and day membrane tanks at wastewater treatment plants in Bedok and Ulu Pandan, Singapore. During commissioning, the energy demand of the MBRs was dramatically decreased by increasing the amount of treated water that was calculated by flux. After commissioning, MBR minimum specific energy demand was 0.57 kW·h/m3 in the case of 33-lmh flux operation. Based on the MBR–RO pilot test for treating municipal wastewater, suitable MF and RO flux were 35 lmh and 20.8 lmh, respectively, without clean-in-place procedures for a longterm operation. For stable operation of the RO process, chloramines had a positive effect on RO membrane permeability. It was demonstrated that high-quality product water, stable MF/RO membrane operation, and low energy consumption could be achieved with MBR–RO.

Infrastructure optimisation via MBR retrofit: a design guide

Wastewater management is continually evolving with the development and implementation of new, more efficient technologies. One of these is the Membrane Bioreactor (MBR). Although a relatively new technology in Australia, MBR wastewater treatment has been widely used elsewhere for over 20 years, with thousands of MBRs now in operation worldwide. Over the past 5 years, MBR technology has been enthusiastically embraced in Australia as a potential treatment upgrade option, and via retrofit typically offers two major benefits: (1) more capacity using mostly existing facilities, and (2) very high quality treated effluent. However, infrastructure optimisation via MBR retrofit is not a simple or low-cost solution and there are many factors which should be carefully evaluated before deciding on this method of plant upgrade. The paper reviews a range of design parameters which should be carefully evaluated when considering an MBR retrofit solution. Several actual and conceptual case studies are considered to demonstrate both advantages and disadvantages. Whilst optimising existing facilities and production of high quality water for reuse are powerful drivers, it is suggested that MBRs are perhaps not always the most sustainable Whole-of-Life solution for a wastewater treatment plant upgrade, especially by way of a retrofit.