RO Plant Research Articles

Performance simulation of solar-driven absorption heat pump-membrane distillation system for combined desalination brine concentration with feed recirculation and cooling applications

Desalination is the primary choice for securing freshwater provision in water-stressed regions and reduces the gap between rising demand and dwindling natural freshwater resources. However, global desalination plants are dominated by fossil fuel-driven desalination technologies with a 40–50 % recovery ratio. Hence, it is critical to decarbonize desalination and address brine effluent ecological concerns. In this paper, a solar-powered absorption heat pump (AHP)-membrane distillation (MD) system concept was proposed and analysed for small-scale RO plant brine reject management and space cooling applications. The MD subsystem is based on commercial MD modules with batch feed recirculation to reach saturation (from 70 to 260 g/kg salinity). The MD system's heating and cooling consumptions are supplied by the AHP (6.54 MWh and 13.47 MWh, respectively, for a complete batch cycle). The AHP is designed to supply hot water at 85 °C with 701.63 kW heating capacity and co-produced chilled water at 16 °C with a cooling capacity of 857.86 kW, about 67 % is utilized to cool down the brine reject to feed temperature. The thermal and exergy COPs were 1.273 and 0.40 at a driving heat of 135 °C. The solar-powered AHP-MD system is useful for sustainable desalination deployment besides space cooling applications.

Assessment and characterization of solid and hazardous waste from inorganic chemical industry: Potential for energy recovery and environmental sustainability

Rapid global urbanization and economic growth have significantly increased solid waste volumes, with hazardous waste posing substantial health and environmental risks. Co-processing strategies for industrial solid and hazardous waste as alternative fuels highlight the importance of integrated waste management for energy and material recovery. This study identifies and characterizes solid and hazardous industrial wastes with high calorific values from various industrial processes at Nirma Industries Limited. Nine types of combustible industrial wastes were analyzed: discarded containers (W1), plastic waste (W2), spent ion exchange resins from RO plants (W3), sludge from effluent treatment in soap plants (W4), glycerine foot from soap plants (W5), rock wool puff material (W6), fiber-reinforced plastic waste (W7), spent activated carbon (W8), and spent cartridges from reverse osmosis plants (W9). Physical characterization, proximate and ultimate analysis, heavy metal concentration evaluation, and thermogravimetric analysis were conducted to assess their properties, revealing high calorific values exceeding 2500 kcal/kg. Notably, W1 and W2 exhibited the highest calorific values (∼10,870 kcal/kg), followed by W6 and W8 (∼6000 kcal/kg) and W9 (∼8727 kcal/kg). Safe heavy metal levels are safe, and high calorific values support the prospects of energy recovery and economic and environmental benefits, reducing landfill reliance and enhancing sustainable waste management.

Simulation and optimisation of a medium scale reverse osmosis brackish water desalination system under variable feed quality: Energy saving and maintenance opportunity

In this work, we considered model-based simulation and optimisation of a medium scale brackish water desalination process. The mathematical model is validated using actual multistage RO plant data of Al- Hashemite University (Jordan). Using the validated model, the sensitivity of different operating parameters such as pump pressure, brackish water flow rate and seasonal water temperature (covering the whole year) on the performance indicators such as productivity, product salinity and specific energy consumption of the process is conducted. For a given feed flow rate and pump pressure, winter season produces less freshwater that in summer in line with the assumption that winter water demand is less than that in summer.With the soaring energy prices globally, any opportunity for the reduction of energy is not only desirable from the economic point of view but is an absolute necessity to meet the net zero carbon emission pledge by many nations, as globally most desalination plants use fossil fuel as the main source of energy. Therefore, the second part of this paper attempts to minimise the specific energy consumption of the RO system using model-based optimisation technique. The study resulted not only 19 % reduction in specific energy but also 4.46 % increase in productivity in a particular season of the year. For fixed product demand, this opens the opportunity for scheduling cleaning and maintenance of the RO process without having to consider full system shutdown.

A Machine Learning Framework for E. coli Bacteria Detection and Classification

Water plays an important role in physiological processes, such as the body's thermal equilibrium, the transfer of nutrients to the intended destination through the body, and the lubrication of joints. In Pakistan, the existing water availability is about 79%. Inadequate and adequate drinking water quality is a significant public health concern. In the project, we explain different machine learning techniques which are used to locate exact bacteria in a water sample, their shape, and scale. This technology promises sufficient identification and division. This invention allows for early identification of bacterial water pollution, requires minimal labor, etc. A robotic frame will speed up the treatment period without human power. It will reduce water emissions dramatically. The methods available for bacterial detection are effective but require lengthy waiting periods for results and expensive and laborious equipment. Via images with PYTHON (Its libraries), this research aims to detect bacteria utilizing images. This system tends to be effective and efficient way for water quality monitoring in different sectors in Pakistan. E.g., Wastewater treatment plants, Power plants, Industries, RO plants, and Laboratories.

Impact of Entry Point Activities (EPAs) on Changes of Socio-economic Conditions of Watershed Community in the Devipatnam Mandal of East Godavari District, Andhra Pradesh

The Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) watershed development program was implemented in the Devipatnam mandal of the west Godavari district of Andhra Pradesh. Introducing watershed development programs to the community through Entry Point Activities (EPAs) has always been recognized as an important activity. The Entry Point Activities (EPAs) were implemented to establish togetherness with the community, strengthening and sustaining it throughout the program and beyond. The present study focused on the assessment of outcomes from Entry Point Activities and their impact on changes inthe socio-economic conditions of the watershed community. The study covered two PMKSY Projects covering four micro watersheds of Batch-V sanctioned in Devipatnam mandal of East Godavari district in Andhra Pradesh. Stratified random sampling was adopted for this study covering 5% of households out of the total households in the study area. Three types of EPAs (RO Plant, Tent houses and Solar street lights) were executed in PMKSY project areas which bring changes in the socio-economic conditions of the watershed community.

Prediction of particulate fouling in full-scale reverse osmosis plants using the modified fouling index – ultrafiltration (MFI-UF) method

This study aims at applying and verifying the MFI-UF method to predict particulate fouling in RO plants. Two full-scale RO plants treating surface water, with average capacity of 800–2000 m3/h, were studied. Firstly, the MFI-UF of RO feed and concentrate was measured using 5–100 kDa membranes at same flux applied in the RO plants (20–26 L/m2.h). Subsequently, the particle disposition factor (Ω) was calculated to simulate particle deposition in RO cross-flow filtration. Finally, particulate fouling rates were predicted based on MFI-UF and Ω, and compared with the actual fouling rates in the plants. For plant A, the results showed that the fouling rates predicted using MFI-UF measured with 100 kDa membrane have the best agreement with the actual fouling (with 3–11 % deviation). For plant B, the fouling rates predicted based on both 10 and 100 kDa membranes agree well with the actual fouling (with 2 % and 15 % deviation, respectively). However, the fouling predicted based on 5 kDa membrane is considerably overestimated for both plants, which is attributed to the effect of the low surface porosity of 5 kDa membrane. More widespread applications of MFI-UF in full-scale RO plants are required to demonstrate the most suitable MFI-UF membranes for fouling prediction.

Management of reject water in decentralized community RO plants by devising an integrated treatment scheme of NF and RO by pilot-scale analysis

Community RO plants have been installed in the semi-arid state of Rajasthan in India to provide potable water to the scattered rural settlements by treatment of brackish groundwater. Presently, these are using standalone RO systems which are operating at low recovery along with the problem of early membrane scaling. To ensure sustainability and maximize the recovery of fresh water, hybrid configurations of membrane processes must be evaluated. In this work, it is aimed to design a conclusive hybrid scheme of NF and RO to deliver maximum freshwater recovery. Firstly, the individual performance of NF and RO in a two-pass NF-RO configuration is evaluated i.e., the removal of ions with respect to feed concentration, ionic radius and hydration radius. The removal efficiency was 85% for sulphate, 54% for calcium and 56% for magnesium by NF. The scaling potential of the water greatly reduced as indicated by the LSI and RSI values by NF pre-treatment. The characterization of RO and NF by FESEM-EDS and FTIR Spectroscopy showed numerous peaks in NF as compared to RO corresponding to inorganic scaling. The specific energy consumption for NF, RO and two-pass NF-RO was 0.13–0.27 kWh/m3, 0.04–0.08 kWh/m3 and 0.17–0.35 kWh/m3, respectively. Based on the performance of standalone NF, RO and two pass NF-RO, mathematical simulations were performed to derive best configurations for NF-RO integration. The resulting configuration, a two stage RO-NF with NF permeate blending to the raw water, resulted in a recovery of 70–80% which was ∼50% higher than the two-pass NF-RO scheme.

Installation of the Brackish Water Reverse Osmosis System Coupled with Solar Power for Drinking Water Production in Ben Tre, Vietnam Considering Water Usage and Cost

Recently, the unbalanced water demand and supply have been occurred globally due to the climate change, industrialization, and population increase. The water shortage problem became much severe in the developing countries because the low-stage of infrastructure might result in frequent limitation of water and transportation of water. Therefore, sustainable water supplying option is the key for the boosting the local economy. The Mekong Delta area produce most of the products in agriculture and fishery in Vietnam. However, due to low income and vast area, the infrastructure for water supply has been limited in the Mekong Delta area. Moreover, due to reduced Mekong-river flow by the dam construction in upper reaches, increased seawater level by the global warming, and increased unexpected drought and flooding by the climate change, the water supply in the Mekong delta is becoming hard. Therefore, sustainable water supplying option was required. In this study, the reverse osmosis-based desalination process could use undrinkable saline water as the feed water coupled with photovoltaic panel was suggested. In order to install the decentralized and off-grid type water production plant in the proper place in the Mekong Delta, the KIST, VKIST, and central and local governments in Vietnam collaborated. The RO plant could be successfully installed by the help of the partners and the operational conditions have been monitored. If the water providing option could be separated according to the purposes such as drinking usage and other water usage, the more technical options could be applied for the water production.

Improving MFI-UF constant flux to more accurately predict particulate fouling in RO systems: Quantifying the effect of membrane surface porosity

This study aimed to quantify the effect of membrane surface porosity on particulate fouling predicted by the MFI-UF method at constant flux. Firstly, the surface porosity of polyethersulfone UF membranes (5–100 kDa) was determined using ultra-high resolution SEM. Thereafter, the MFI-UF was measured using suspensions of polystyrene particles (75 nm), which were pre-washed to remove surfactant and particle fractions smaller than the pores of MFI-UF membranes, thus ensuring complete retention of particles during MFI-UF measurements. Consequently, the MFI-UF values of washed polystyrene particle suspensions were independent of the pore size and depended only on the surface porosity of MFI-UF membrane. The results showed that the membrane surface porosity decreased with MWCO from 10.5% (100 kDa) to 0.6% (5 kDa), and consequently the MFI-UF increased from 3700 to 8700 s/L2, respectively. This increase in MFI-UF was attributed to the non-uniform distribution of membrane pores, which is exacerbated as surface porosity decreases. Consequently, preliminary correction factors of 0.4–1.0 were proposed for MFI-UF measured with UF membranes in the range 5–100 kDa. Finally, the surface porosity correction was applied to predict particulate fouling in a full-scale RO plant. However, additional research is required to establish correction factors for different types of feed water.

Management of Reject Water in Decentralized Community Ro Plants by Devising an Integrated Treatment Scheme of Nf and Ro by Multi-Dimensional Pilot-Scale Analysis

Management of Reject Water in Decentralized Community Ro Plants by Devising an Integrated Treatment Scheme of Nf and Ro by Multi-Dimensional Pilot-Scale Analysis

Water Sustainability: Current and Future Challenges at SRM Institute of Science and Technology, Chennai, India

SRMIST has healthy approach to sustainability, incorporating social economic and environmental principles that have been in place for nearly a decade implementing short and long-term sustainable objectives. SRMIST developed, maintained the estate, and the surrounding landscape, with due environmental impact and social values and implemented effective, efficient utility management measures, policies and procedures. The 2018/2019 UI Green Metric ranked SRMIST as 9 th in India and 392nd in Global Ranking overall and 264th rank globally and 9th rank in India for water parameter and 3rd in the Nation and 243rd globally and 2nd rank nationally and 42nd rank globally for water. SRM IST improved implementation of the water conservation and recycling program from 75% in 2018 to 95 % in 2019. Water efficient appliances increased > 70% and has a long-term commitment for conservation of water by regularly monitoring the use of water with regular meters. SRMIST has 20 RO plants running 24x7 collecting 31,000L per day for all and installing Ultra Filtration unit. SRMIST’s goal is to reduce per capita water consumption varies from 3.7m3 to 3.3m. Among the 4600 M3 waste water generated an average 4140 M3 wastewater is treated and recycled. Rainwater harvesting pits have been constructed in 65% college buildings and hostels is used for the water recharge in the campus and the rainwater stored in the roof tanks are used for toilet flushing.

Impact of Entry Point Activities on The Change of Lifestyle in Watershed Villages

Introducing watershed development programme to the community has always been recognised as an important activity for not only improving the natural resources but also for livelihood development. In Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) projects, entry point activities (EPA) are carried out to establish togetherness with the community, and strengthening and sustaining it throughout the programme and beyond. The present study largely focussed in assessing the outcomes o f EPAs and their impact on the way o f watershed community's life. The study covered all 70 PMKSY Batch-IV projects sanctioned in Prakasam district o f Andhra Pradesh. The sample size under each PMKSY project covered a minimum o f 20 per cent physical verification of the EPAs in the project area on stratified random sampling basis. In all, 19 micro watersheds (MWS) were included in the study. Seven types of EPAs (cattle/goat/sheep water troughs; school-related provisions like furniture, shed, building repair, laboratories; health camps; fertility camps; solar street lights; RO Plants; tent houses) executed in PMKSY projects are rated as Excellent based on TOO per cent achievement of EPA targets; quality & utility of the activities; and status o f functioning. Cash-based EPAs are found to be more effective to build rapport with the community by ensuring perceptible socio-economic benefits for the community.

Performance evaluation and economics of a locally-made stand-alone hybrid photovoltaic-thermal brackish water reverse osmosis unit

Abstract The performance of a developed brackish water reverse osmosis (BWRO) desalination unit integrated with a stand-alone hybrid photovoltaic-thermal (PVT) module was evaluated under the climatic conditions of Tehran (35.68° N latitude 51.42° E longitude). From the experimental results, the maximum surface temperature of the PV module and thermal efficiency of the PVT module were recorded as 60.38 ​°C and 83.7%, respectively at the set-point temperature of 50.00 ​°C for the thermostat, and under the average solar radiation of 971.34 ​W/m2. During the evaluation, the maximum average productivity of the BWRO unit was obtained as 13.98 ​L/h when temperature values of the PV module, soft water, and brackish feed water (BFW) were recorded as 52.94 ​°C, 28.97 ​°C, and 36.60 ​°C, respectively. From the results, it was also found that the temperature of BFW positively affects the PVT module’s thermal performance and improves the whole unit’s productivity. Also, water quality parameters of pH, TDS, EC, and DO for treated water were evaluated. The economic analysis of the system revealed that the cost of the produced freshwater for the BFW’s salinity of 15,000 ​ppm is 18.96% higher in comparison with 5000 ​ppm for all cases, indicating a closer value to freshwater cost of conventional large-scale RO plants.

Self-Learning Salp Swarm Optimization Based PID Design of Doha RO Plant

In this investigation, self-learning salp swarm optimization (SLSSO) based proportional- integral-derivative (PID) controllers are proposed for a Doha reverse osmosis desalination plant. Since the Doha reverse osmosis plant (DROP) is interacting with a two-input-two-output (TITO) system, a decoupler is designed to nullify the interaction dynamics. Once the decoupler is designed properly, two PID controllers are tuned for two non-interacting loops by minimizing the integral-square-error (ISE). The ISEs for two loops are obtained in terms of alpha and beta parameters to simplify the simulation. Thus designed ISEs are minimized using SLSSO algorithm. In order to show the effectiveness of the proposed algorithm, the controller tuning is also accomplished using some state-of-the-art algorithms. Further, statistical analysis is presented to prove the effectiveness of SLSSO. In addition, the time domain specifications are presented for different test cases. The step responses are also shown for fixed and variable reference inputs for two loops. The quantitative and qualitative results presented show the effectiveness of SLSSO for the DROP system.

Phosphorus-Doped Carbon Quantum Dots as Fluorometric Probes for Iron Detection.

Carbon quantum dots (CQDs), a novel fluorescent nanomaterial, have been extensively employed/explored in various applications, that is, biosensors, bioimaging, nanomedicine, therapeutics, photocatalysis, electrocatalysis, energy storage system, and so forth. In this study, we report the synthesis, characterization, and the application of phosphorus-doped CQDs (PCQDs), synthesized using trisodium citrate and phosphoric acid by the hydrothermal method. The effect of phosphorus doping on optical features and the formation of PCQDs have been explored elaborately by controlling the concentrations of precursors, reaction time, and the temperature. The fluorescent quantum yield for PCQDs was determined to be 16.1% at an excitation/emission wavelength of 310/440 nm. Also, the optical and structural properties of PCQDs were determined by using various spectroscopic and microscopic techniques. Static quenching of fluorescence was determined upon the addition of Fe3+ to PCQDs because of the formation of the fluorescent inactive complex (PCQDs–Fe3+). Hence, this chemistry leads to the development of a new fluorometric assay for the detection of Fe3+. The lower limit of Fe3+ detection is determined to be 9.5 nM (3σ/slope), with the linear fit from 20 nM to 3.0 μM (R2 = 0.99). We have validated this new assay in the raw, ejected, and purified water samples of the RO plant by the standard addition method. These results suggest the possibility of developing a new commercial assay for Fe3+ detection in blood, urine, and various industrial waste and sewage water samples. Furthermore, recycling the pollutant water into the freshwater using filters that consist of PCQDs offers a great deal.

Characterization and analysis of inorganic foulants in RO membranes for groundwater treatment

Thousands of small community-based RO plants have been installed in Rajasthan in the last few years by Public Health Engineering Department in compliance with the national guidelines. Recent reports from plant managers have indicated substantial premature replacement of RO membrane modules due to accelerated fouling. This paper describes the performance analysis of community RO plants in Bharatpur having high total dissolved solids in groundwater and attempts an ion balance to understand the fouling problem through chemical analysis of raw, permeate and reject water samples. The analysis gives new insights to field operations of brackish water systems indicating that in the majority of these plants, CaCO3 was the main foulant as per SEM-EDS; attributed to high hardness, relatively lesser solubility of hardness causing substances over sodium chloride, and inverse solubility-temperature behavior of CaCO3; water temperature being higher in Rajasthan compared to that of coastal areas. Oxides of Fe and Mn were other major foulants as they are sparingly soluble in water; thus precipitate immediately and foul the membrane. Cleaning efficiencies of HCl and citric acid were also investigated. An optimum time of 9 h cleaning through citric acid was found best while use of HCl resulted in damaging polysulfone support layer.

Monitoring and Intelligible Alert System to control Water Quality in Reverse Osmosis Plants

The classification of drinking water quality severity from RO production plant needs appropriate methods to provide intelligible alert to the operators who involve to carry out remedial action in pace with the production. The proposed technique finds more relevance to detect instantly the quality variations in plant through efficient classification system and drives to reduce the cumbersome of operators. In this paper, it is proposed a SVM based classification method to detect drinking water quality attributes temporally and then precisely classifying severity condition in order to correct quality derivations. A different control scheme is experimented to detect quality variables like pH, TDS, ORP and EC and to support production system. Thus this contributes an automated diagnosis of water quality in RO plant. For classification, SVM is trained with data obtained around 8 plants from West and North of Chennai region. This is demonstrated specifically for a top-level classification job on Quality. On the features extracted from 1280 data, the SVM is trained and achieves a sensitivity of 85% and an accuracy of 90%

Prediction of capital cost of ro based desalination plants using machine learning approach

This paper presents a neural network tool for predicting the capital cost of desalination plants based on reverse osmosis technology. A multi-layer feedforward neural network with back propagation learning method is used to model the investment cost of RO plants. The model is developed using the data sets of 1806 RO plants of capacity at least 1000 m3/day, which involved training, testing and validation. The model used six inputs that included both categorical and numerical data elements, namely: plant location, plant capacity, project award year, raw water salinity, plant types, and project financing type. The output is the capital cost of the RO plants planned. This prediction model can be used by governments, investors or other stakeholders in desalination industry to make a reasonable estimate of investment costs of upcoming RO plant projects.

Nanofiltration as a cost-saving desalination process

The water is a basic need for life including human beings, animals, plants, and microbial life. Although almost 75% of globe is covered by water in the form of oceans, only a small percentage of water is usable by living beings due to various salt content, pathogens, and contaminants. Good-quality water is highly scarce in dry regions of the world like Gulf Cooperation Council, South Asian and African countries. It is believed that the limited water supplies of water may worsen due to the inception of climatic changes ahead. The only alternative source is desalination of seawater/saline water. The traditional desalination technology is improving due to introduction of nanotechnologies like nanofiltration. The present studies were conducted at the research farm of Ministry of Municipalities and Environment (MME), Doha Qatar for 3 years (2016–2018). RO and nanofiltration plants were procured and installed at the research farm of MME. Electricity consumption was recorded, and quality of various types of water: feed water, product water, and brine water, was regularly monitored. The results of the study indicated that nanofiltration desalination process proved as effective as the RO but consumed 29% lesser energy. Therefore, the cost of water production was lessened by 29%, thus making the desalination technology as cost-saving and feasible.

A hybrid reverse osmosis/adsorption desalination plant for irrigation and drinking water

The hybridisation of brackish water reverse osmosis (BWRO) desalination technology and an adsorption cycle (AD) are considered in this work as a means of producing large quantities of a) water for irrigation and; b) high quality water for domestic use. The RO process and the AD cycle are represented as numerical models and have been optimised to produce fresh water and cooling. An existing RO plant can be retrofitted to become an RO-AD process to improve its specific energy consumption and simultaneously produce a cooling effect which can be exploited for local process cooling or air conditioning. A pressure exchanger (PX) and AD are combined to recover the reject from the RO, resulting in reduction in power consumption. The hybridised RO-AD desalination processes can be considered as the optimum solution for rural areas due to its capability for the production of water for irrigation and drinking as well as cooling for air-conditioning. Nevertheless, the temperature and feed salinity may negatively effect on RO production, with the AD cycle producing more than 6 m3/tonne s.g of drinking water (<15 ppm) at 85 °C, additionally the AD evaporator is not effected significantly by salinity. The proposed plant could produce 24,000 m3/day for irrigation and 6.3 m3/tonne s.g for drinking as well as 75 RTon/tonne s.g. Another interesting finding was that the minimum specific energy for the combined RO-PX-AD plant with a capacity of 24,000 m3/day is 0.8 kWh/m3 at RO recovery = 45%. The small-scale combined system was also examined to produce 2000 m3/day and cost of different configurations was estimated as well. The results showed that the cost of the combined RO-AD system is the lowest, 0.44 £/m3 compares with other RO configurations.