A Case Study About Treatment of High Salinity Agrochemical Wastewater
This case study is all about electrochemical oxidation treatment of high salinity agrochemical wastewater polluted by a wide range of pesticides such as Acetamiprid, Imidacloprid, Malathion, Nicosulfuron, Imazethapyr, and Clethodim, coupled with high salinity of 14.18% sodium chlorides.
The pesticide manufacturer contacted Boromond engineering team to inquire about different approach rather than conventional wastewater treatment methods as traditional treatment technology seem insufficient according to treatment results from previous treatability testing and trial testing of other wastewater treatment services.
Basic Situation of Agrochemical Wastewater Treatment Project
In this context, we present basic situation of this agrochemical wastewater treatment project, information of the raw water mainly encompasses types of water, sources of water, and major pollutants, and then initial COD and TOC level, and ammonia content, total nitrogen, pH value, and total phosphorus.
Agrochemical Wastewater types
Agrochemical wastewater from pesticide and herbicide manufacturing sites, it’s likely to have cholrine and benzene organic compounds
Sources of Agrochemical Wastewater and Minor Waste Streams
Pesticde wastewater are mainly from pesticide and herbicide manufacturing processes, and there are different production line encompassed manufacturing and packaging of Acetamiprid and imidacloprid, malathion, nicosulfuron, imazethapyr, clethodim and etc.
Pesticide wastewater with this specific pesticide manufacturer are mainly originated from major steps and processes such as systhesis, manufacturing, find out more from the content below:
Production and Formulation:
Cleaning and Equipment Maintenance:
Cooling and Heating: These processes can also generate wastewater, particularly in liquid pesticide formulation.
Production Processes: The manufacturing process itself generates wastewater containing chemical residues, active pesticides, and other byproducts.
Synthesis and Refining: Steps such as using autoclaves, fermentation vessels, refining equipment, drying equipment, and separation equipment can generate wastewater.
Preparation and Post-treatment: These steps in the production of pesticides contribute significantly to wastewater generation.
Auxiliary Processes:
Cooling and Heating: Circulating cooling water systems and heating processes contribute to wastewater volumes.
Vacuum Equipment and Waste Gas Treatment: These processes can also generate wastewater.
Laboratories: Laboratory activities involving chemicals and testing contribute to wastewater.
Daily Maintenance and Formulation:
Equipment Washing: Cleaning of blending tanks, mixing equipment, and other process areas can lead to wastewater generation, washing of equipment, lines, and process areas, especially between batches of different products, is a major source of wastewater.
General Cleaning: Flushing of floors and process areas generates wastewater.
Rainwater: Initial rainfall in and around processing areas can become contaminated and require treatment.
Main pollutants, special substances and content within the agrochemical wastewater
Mixed wastewater from various manufacturing processes and steps of pesticides and herbicides including Acetamiprid, Imidacloprid, Malathion, Nicosulfuron, Imazethapyr, and Clethodim and etc, different types of organic pollutants and intermediates, the specific content is unknown yet prior to trial testing on electrochemical oxidation.
Main salt components and their relevant content in this agrochemical wastewater
There was a total amount of 18,000 cubic meters in existence, some 9000 tons of high salinity agrochemical wastewater, and these , with a sodium chloride content at 14.18%, and the pesticide production lines have been shut down temporarily to prepare new approach to treat the high salinity agrochemical wastewater, therefore there will be no new waste streams prior to complete installation, and routine operations of the new wastewater treatment technology. Our engineering team are expecting a daily wastewater processing capacity of 50 tons.
Major Parameters of this agrochemical wastewater
COD at 107200 mg/L
TOC at 34000 mg/L
Ammonia at 378 mg/L
Total nitrogen value was not recorded with this project
pH value at 5.87
And this agrochemical wastewater is with a total phosphorus of 618 mg/L
Challenges with Agrochemical Wastewater
Based comprehensive study and further investigation of the major parameter of this specific agrochemical wastewater, our wastewater treatment engineering advisors comprehend there are several challenges with this customer now are:
The pesticides such as Acetamiprid and imidacloprid, malathion, nicosulfuron, imazethapyr, clethodim and etc, are known organic pollutants in water bodies, posing risks to aquatic life and potentially human health. Persistent organic pollutants such as imidacloprid and acetamiprid and etc are recalcitrant and refractory to conventional treatment methods, for example, biological treatment may not be effective to remove pesticides content, which means it’s critical to locate some new approaches to remove these pesticides.
With a sodium chloride content at 14.18%, this wastewater is considered a waste stream with high salt concentrations can mitigate the activity of microorganisms and impact the efficiency of some physical and chemical treatment processes.
What is more, how to remove ammonia and nitrogen in such a low pH value since the main target of the desired treatment results or goals are set to removal of organic pollutants, that directly reflecting on the TOC and COD removal rate.
Electrochemical Oxidation Solution Toward Agrochemical Wastewater
Boromond is one of the leading manufacturers of electrochemical oxidation wastewater treatment products, and optimal electrochemical oxidation wastewater treatment solutions and services, therefore Boromond engineering team proposed advanced electrochemical oxidation technology to treating agrochemical wastewater containing pesticides like Acetamiprid, imidacloprid, malathion, nicosulfuron, imazethapyr, clethodim, and etc, with high salt concentrations, low pH value, and high concentration level of ammonia conditions.
The advanced electrochemical oxidation technology involves direct and indirect oxidation, there are several advantages toward conventional treatment methods:
Electrochemical Advanced Oxidation Processes (EAOPs) can destroy a wide range of pesticides efficiently in a non-selective nature (we will explain the mechanisms and mineralization processes, results of major pesticides such as Acetamiprid, imidacloprid, malathion, nicosulfuron, imazethapyr, clethodim and other pesticides considered persistent pollutants with different contents, therefore stay tune with us).
Electrochemical Advanced oxidation processes (EAOPs) can degrade pesticides with complex molecular structures into substances and intermediates that are less harmful, and complete mineralizations of these pesticides into inorganic compounds, water and carbon dioxides.
Electrochemical oxidation have been implemented to treat pesticide wastewater with high salinity.
Ammonia molecules can be oxidized directly at the surface of the anode via direct electron transfer among these molecules and the anode, convert ammonia to nitrogen gas, electrochemically generated highly reactive species oxidize nitrogen compounds, reduce total nitrogen content.
Our trial and bench testings suggest that a lower pH values can actually expedited better COD removal efficiency in electrochemical advanced oxidation processes.
Our engineering team always deliver effective and cost efficient technical advices and solutions in the planning, design, prototyping and operation of wastewater management facilities.
Therefore we developed several prototypes as proof-of-concepts experimental products for treatability testing of this agrochemical wastewater via 3D printing additive manufacturing to evaluate performance and optimize designs, prior to full-scale implementation and handling larger flow rate.
Experimental Set-up for Electrochemical Oxidation Treatment of Agrochemical Wastewater
This experiment uses the principle of electrochemical oxidation and uses BDD electrode as the core reaction device to finally convert the organic matter in the water sample into CO2 and H2o.
Electro oxidation requires applying electrical energy, electron trafer between the electrolyte, and anode was expedited once electricity applied, certain organic pollutants could be mineralized directly around the surface while electron transfer processes happen between the anode and electrolyte, that is the mechanism of direct oxidation within electro oxidation processes. 
Indirect oxidation invloves generation of active oxidizing agents such as hydroxyl radicals (OH), with higher oxidation potential amongst its types and other highly active radicals, for instance, sulfate radicals (SO) within the electrolytic reaction processes, migrate into the solution. Radicals mineralize organic matters by breaking chemical bonds such as C-C, C-N, and etc, and degrade into ingranic forms (H2O, CO2, etc,) or simpler organic compounds as intermediates with smaller molecules could be mineralized with further oxidation via a vast variety of pathways, and eventually degraded, instead of concentrated, does not for further treatment afterwards.
Electrochemical Reactor for Electrochemical Oxidation Treatment of Agrochemical Wastewater
We developed and then fabricate an basic components, an electrolysis cell with electrode stacks made of boron doped diamond BDD anodes and Titanium cathodes, to function an light-weight electrochemical reactor dedicated to treat this specific agrochemical wastewater, it’s a new apporach to conduct treatability testing and locating a way to realize bench scale testing and pilot scale enigneering solution toward these pesticide wastewater.
Electrode stacks with two boron doped diamond BDD anodes and three Titanium cathodes are placed within a beaker at size of 1000 mL, with supporting pipes and exhuast auxiliary holes ready, therefore we can intialize trial testing of pesticide wastewater via electrochemical oxidation treatment technology once electricity applied, while monitoring and controlling the voltages and current, to keep the current density at a controllable level.
Anode
Considering about required long time operation and electrocatalyst capability of the needed anode, we selected boron doped diamond BDD electrodes with silicon substrates as anodes for the electrochemical reactor, BDD anodes have unmatched performances with direct oxidation of persistent pesticide molecules via direct electron transferring among the anodic catalyst materials and pesticides molecules.
Given the wider electrochemical potential window and capability to generate reactive oxidizing agents to realize indirect oxidation of pesticide molecules and other persistent organic pollutants, the anodes are with a surface area of 200 square centimeters.
Cathode
Three titanium electrodes are selected as cathodes, combination of BDD anode and titanium cathodes emited so far the best performance within our conceptual design and prototyping processing, electrode stacks with the BDD anodes and Titanium cathodes, both are non-active electrodes, demonstrated the great oxygen evolution overpotential and oxidation power, and hydroxyl radicals and other reactive oxygen species could be generate via electrogeneration processes, and adsorbed on the BDD anodes with proper boron content, surface termination and etc.
Cell And Supporting Accessories
Electrochemical reactor require a DC power supply that can provide the necessary voltage and current to drive the electrochemical reaction. Usually electrochemical reactors require a voltage range between some 2.5V and 6V, sometimes these reactors operates at 4-5.5 V. We used a switching mode power supply to ensure efficient outputing of a stable current.
A custom made glass beaker at 1000 mL as container of electrolytes, and main location for the electrochemical oxidation and reduction reaction.
A lid over the beaker to acting as protective barriers, and then ensure the integrity and process control of the experiments, with access to intaking and effluent extraction spots.
Experimental Preparation And Operation
Take 900 mL of water samples and place them in the electrochemical oxidation beaker module with the actual working area of 150cm2 at the anode, heat the water sample to a constant temperature of 7oC, connect the power supply, adjust the current intensity to 4.5A, the experiement begin instantly.
During the experimental process, the water sample was stirred with a magnetic stirrer to make it uniform. Samples are taken at regular intervals, the current and voltage values are recorded, and the temperature and pH value is measured.
Experimental Results
Before degradation, the water sample was brown-blackish.
The color faded gradually during the experimental processes, a small amount of brown precipitation was produced.
Check the above chart to find out the treatment processes and results of relevant steps and processes:
Pesticides wastewater with high cocentration of ammonium salt
Mesuring parameters is TOC at mg/L
Status/Experimental Time TOC Value (mg/L) *Notes/Mark
Raw Water 34,000 At 70 degree celsius
26 hours 20,430 At 70 degree celsius
31 hours 21,230 At 70 degree celsius
44 hours 14,450 At 70 degree celsius
49 hours 11,470 At 70 degree celsius
54 hours 7,609 At 70 degree celsius
67 hours 2,131 At 70 degree celsius
82 hours 149 *Low temperature, below 70 degree celsius
Bench Scale And Pilot Engineering Solution Toward Agrochemical Wastewater
Our enigneering team managed to pull out a full scale electrochemical oxidation wastewater treatment system with electrochemical oxidation modular treatment units, control panel, and holding tanks for on-site constant treatment of this agrochemical wastewater.
Factors And Consideration After Trial And Bench Testing Treatment of Agrochemical Wastewater
While lower pH can expedited COD removal, some moderate alkaline conditions are generally more favorable for the efficient removal of ammonia via electrochemical oxidation processes.
The selecting of electrode material, especially the anode, impact the overall efficiency and cost of the electrochemical oxidation treatment process, therefore it’s critical to consider about the electrocatalytic capability, corrosion resistance, conductivity, surface for oxidants and pollutant adsorbtions.
Given the truth that electrochemical oxidation technology is efficient when it comes treatment of complex organic wastewater, it can also be costy, as the degradation and mineralization processes consume huge amount of electric energy, in this case, it’s critical to optimize parameters such as current density and retention time, electrode spacing, and flow rate, electrochemical reactor designs, and adopting of renewable energy to enhance efficiency and reduce costs.
Even if the major target of utilizing electrochemical oxidation wastewater treatment technology is complete mineralization of pesticides and herbcides, the formation of intermediates and possible harmful byproduct requires constant monitoring and control within the whole processes, therefore it’s critical to mitigate the byproduct generations.
