Analysis and treatment of Reverse Osmosis (RO) reject water and organic waste using Mist reactor


Reverse osmosis (RO) is one of the wastewater treatment processes that remove the concentrate in the form of dissolved impurities in the raw wastewater. The treated reject released during the RO process remains a major polluting problem. The RO reject, with high solid concentration, needs maximum purification. It is one major problem prevailing in the many industries where RO was mainly used as tertiary treatment to achieve zero discharge effluent. Approximately one-third of the total quantity of wastewater concentration was rejected and collected as RO reject in many industries. This concentrated RO rejects stream seems to be more toxic than non-treated wastewater. To overcome this difficulty Mist reactor study was initiated. It was necessary to find a potential solution to treat RO reject-with by-product recovery as the existing methods for treating RO reject is open dumping in the sea, discharge in sewer or swamps, as a dewatering process, disposal in water bodies. MIST REACTOR study was carried out on a lab-scale using RO as feeding material. In this investigation, the anaerobic biotreatment process was carried out to reduce the Biological Oxygen Demand (BOD) concentration. MIST REACTOR has the advantage of operating at even reduced flow rates to ensure contact between the RO reject feed and our mist tank. As a result of the Mist chamber with duct, MIST REACTOR will produce water vapor as a product. By investigating various characteristics, it was observed that there is a consequential percentage decrease in Biological oxygen demand (55% – 80%), Chemical oxygen demand (COD) (65% – 80%), Chlorides (75% – 90%) and Alkalinity (75% – 85%).


The invention relates to the technical field of Ro wastewater treatment, in particular, to reverse osmosis (RO) water purifier wastewater recycling system.

AWGs are an ideal solution for drinking water in areas that are remote and have sparse groundwater. However, their use is restricted to areas with high humidity as the output is proportionate to the humidity levels. To tackle this problem and make water available to all locations irrespective of terrain, humidity, and groundwater availability, AeroNero presents an alternate solution.

Most cities use RO filters for drinking water. A large amount of the wastewater generated is usually discarded due to its high salinity and lack of purpose. We use this wastewater to produce clean drinking water with our remarkably simple and effective method which we call ‘MIST’. Our Mist generator is fed with RO wastewater. This water is converted to mist and sprayed into the air. As the mist works its way around the room, it increases the humidity. This makes the environment ideal for our atmospheric water generator to function. The output of water is increased due to high humidity. Thus, we provide water to low humid areas, reuse RO wastewater, and produce drinking water. All in one shot.

The system can effectively solve the problem that wastewater is hard to utilize and meanwhile can reduce the water making cost. The system structurally comprises a water storage container. The water storage container is provided with a water inlet which is connected to the wastewater pipe of a RO water purifier. The water level controller monitors the amount of water stored in the tank. Once it has reached the set level, it switches on the Mist system. This is a set of nozzles that releases a fine spray of water by changing the vapor pressure of the water. These nozzles can be arranged horizontally to fall like rain or vertically to shoot directly at the water generator water generators that are placed adjacent. This process increases the relative humidity, triggering our unique architectural system inside our water generator and this generation of clean water begins.

Cons of RO waste

The Brine Reject (RO Reject) is disposed into the water bodies have an impeding effect on aquatic environments. There are a number of finishing processes in the dyeing industry and every finishing process results in water pollution. It therefore evident that purification of the reject water is necessary before it is let out into the environment.

It was predicted that around the year 2025 almost two-thirds of the world populace would have to face the ill effects of water contamination due to several aspects of pollution and over-exploitation of natural resources.

It is hence necessary that the concentrate of RO from many industries should be treated and disposed of efficiently as per the regulations of the Environmental (Protection) Act.


The initial study of the sample of RO Reject was collected from the common effluent treatment plant of many industries from Shanghai. The samples were taken are fed into a small-scale reactor placed in the Environmental Engineering lab of BNC, The MIST REACTOR reactor used for treating RO Reject was made up of acrylic material of 5mm thickness. It comprises an arrangement of vertical perplexes that separate it into 5 indistinguishable compartments. The fluid volume of the reactor was 11L and its dimensions are (35 x 17 x 30 cm). A schematic figure of the MIST REACTOR was represented in Figures-1a RO Reject was continuously fed into the reactor with different OLR with the help of a peristaltic pump in order to arrive at the ideal operating conditions of the MIST REACTOR.

The RO reject sample was collected from Common Effluent Treatment Plant (CETP) which mainly deals with many industries from shanghai in china. The initial characteristics of the RO reject are determined. The MIST REACTOR was designed and fabricated by using an acrylic material with six baffles. The generation of water vapor is monitored during the incubation time as well as during the feed process. After the incubation period, the RO Reject sample was fed into the reactor. The final treated sample is analyzed, and the efficiency of the reactor was determined. The pH, Total Dissolved Solids (TDS), Total Suspended Solids(TSS), Total Solids(TS), Alkalinity, Chlorides, BOD, and COD variations are determined based on the principles of WHO standard methods of examination of water and wastewater based upon APHA standards in vogue.

Fig.-1a: Schematic representation of the Mist Reactor

Fig.-1b: Experimental setup of the mist Reactor

Results And Discussion

The influent wastewater was diluted in a ratio such that the influent COD was reduced to 300mg/l, 600 mg/l, 800 mg/l and then the raw influent (RO Reject) 1200 mg/l COD was fed into the reactor. The influent wastewater was fed by a peristaltic pump the effluent was collected through the outlet and then various parameters are analyzed and the results are represented in Table-1 and 2

Table-1: Influent and Effluent Characteristics of RO Reject

S. No.ParametersInitial CharacteristicsInfluentEffluentInfluentEffluent
7BOD ppm57045504048
8COD ppm2150180200130178

Table-2: Influent and Effluent Characteristics of RO Reject

S. No.ParametersInitial CharacteristicsInfluentEffluentInfluentEffluent
7BOD ppm57026752470
8COD ppm2150120182109208


The efficiency of removal with high influent concentration was found to be (55% – 80%) of BOD removal, (65% – 80%) of COD removal, (75% – 85%) of alkalinity, (75% – 90%) of chlorides. Treatment of wastewater can be further processed in order to reduce the biological contaminants and make it fit for recycling or fertigation process. Water vapor generated can be analyzed by further studying its characteristics so as to improve the efficiency of the treatment process. As there is no efficient treatment method to treat the RO Reject from many industries, this method can be suggested as one of the pre-treatment methods to reduce the concentration of COD in wastewater. If this study was further improved and used for the treatment of other organic waste, the recovered water can then be used for various useful processes like Phytoremediation, garden farming, fertilization, etc.

1. MIST generator – revive wastewater


Reverse osmosis has become a household name in recent years, providing families and institutions with drinking water when other sources have run dry. The disposal of the reject stream produced is an increasing challenge as pollution control agencies ban dumping into landfills due to the likelihood of the highly saline solution leaching into underground aquifers. Cansu introduces a new method to revive clean water from this reject water through the use of the product- MIST.

Working principle

The purpose of this water recovery system is to increase the output of an atmospheric water generator by using wastewater from the RO system in a manner that is profitable to the consumer. The wastewater is fed into the Mist generator that releases a fine spray of water. This increased humidity improves the output of fresh drinking water from the adjacent AWG. In the process of water extraction, the room is also cooled due to evaporative cooling.

Case Study Chile

The Chilean law allows treated wastewater to be used for secondary purposes and prohibits the use for human consumption. Cansu proposes an interesting approach where the wastewater can be indirectly utilized to provide more drinking water, without causing any harm to human life. The suggested system uses wastewater to increase the humidity in the vicinity, creating an ideal environment for extracting water from the air.

The wastewater is first treated with an organic compound that results in clear water. This filtered water is fed into a Mist generator that emanates a fine mist and hovers in the air, increasing the humidity of the area. This activates the atmospheric water generator to run and, in the process, filters the air and the generated water. The freshly generated water undergoes a 4-step filtration process and is fit for human consumption.

2. RECLAIM – wastewater management solution


Every year, 34 Lakhs of children die due to water-borne diseases. 99% of these children are from developing countries. A large number of waterborne diseases originate from human excreta. Wastewater treatment is fundamental in protecting the health of many different ecosystems and is a source of water for many purposes.

Cansu introduces a novel method of wastewater recovery that utilizes an organic solution to separate the clean water from its contaminants. When added to sewage water, the compound quickly flocculates the dirt and its contaminants.

The compound created by Cansu is unique due to its organic constituents which when paired with filtration systems can provide water that is suitable for human consumption. The process also allows speed control, allowing the user to decide the length of time required to complete the process.

Case Study ZENDEN Sustainable home

Zenden is a perfectly designed autonomous home, which is the ultimate in the green living dwelling. These homes rely solely on themselves for water and electricity.

The atmospheric water generators produce drinking water, made by liquefied humidity using electricity from the sun. Bathwater, washing machine (laundry and dish) drains and other outlets are directed to a treatment facility that produces clean water, ready for reuse.

The physical waste separated from the wastewater treatment is compressed and formed into manure for the vegetable garden.

Electricity from the sun powers the machine that produces water from the air. The treated water feeds the vegetable garden and supplies manure.

The solution provided is a combination of AWG THUNDER for 150 liters per day and RECLAIM. The cost to implement the solution is including solar for THUNDER AND RECLAIM is $17500 making this a 100% sustainable home at an affordable capital cost and negligible operational cost

Case Study - Farm

Cansu’s Mist is being used to generate copious amounts of water at a farm in Chennai. Unfiltered water from a well is fed into a Mist generator that sprays a fine mist of water into the air. This spray is inhaled by an atmospheric water generator that produces clean drinking water.

The spray maintains the humidity of the environment allowing the AWG to extract the most amount of water from the air. The resultant water is purified and ideal for human consumption or irrigation. This system generates over 2500 liters each day. Solar Power is used to implement the solution thereby making it completely green. This system costs $20,000 to implement and the operational cost per day is negligible as it is completely driven by solar power