The environmental problems in pig farms have become a key constraint on the efficient and safe production of China's pig farming industry, the main cause of major diseases, and a bottleneck that restricts the overall level of pig farming improvement. Starting from biosafety and healthy breeding, regular disinfection of the breeding environment is an important measure to prevent the occurrence and spread of diseases and create a healthy growth environment for pigs. At present, chemical disinfectants are commonly used in China to control the environmental microorganisms in pig farms. The current disinfectants used in pig farms have more or less problems in terms of antibacterial spectrum, disinfection effectiveness, toxicity, corrosiveness, price, etc., which brings great difficulties to the pig farming industry. How to efficiently, inexpensively, harmlessly, and pollution-free eliminate pathogenic microorganisms from humans, livestock, and equipment has become a difficult and key issue in modern pig farming.

In recent years, the use of electrochemical technology to prepare disinfectants has received increasing attention. Acidic electrolyzed water (AEW), also known as acidic ionized water or acidic redox potential water, has instantaneous, broad-spectrum, residue free, and efficient sterilization characteristics. After sterilization, it can be completely reduced to non-toxic and residue free ordinary water, and discharged without polluting the environment. However, the current strong acidic water electrolysis has the following main problems:

(1) The existing strong acidic water electrolysis equipment has low production efficiency and high manufacturing and operating costs;

(2) Strong acidity (pH<2.7) and certain corrosiveness to metal equipment limit its promotion and application in livestock and poultry breeding;

(3) Strong acidic water electrolysis has unstable physical and chemical properties, fast reduction rate, and is not conducive to storage.

In response to the above issues, research and development have been conducted on Slightly acidic electrolyzed water (SAEW, pH 5.0-6.5) with a pH value close to neutral. Through laboratory experiments, it has been found to have low corrosiveness, stable physical and chemical properties, and can reduce health and safety issues caused by chlorine gas release. At this pH value, chlorine mixtures mainly exist in the form of hypochlorous acid (HClO), which has the strongest bactericidal effect. It has a wide range of applications and is suitable for fields such as medical treatment, agricultural production, food processing, and livestock and poultry breeding. According to research, slightly acidic water electrolysis has a good killing effect on Escherichia coli, Staphylococcus aureus, Salmonella enteritidis, Vibrio and other bacteria. This article mainly introduces the preparation method of slightly acidic water electrolysis; Study the disinfection effect of slightly acidic water electrolysis pig farm with body disinfection on the air, floor, wall and fence inside the pigsty, and compare its bactericidal effect with strong disinfectant powder and povidone iodine solution.

1. Experimental process

1.1 Preparation of Slightly Acidic Water by Electrolysis

The preparation of slightly acidic water electrolysis adopts a diaphragm free electrolysis device, which mainly consists of an electrolytic cell, platinum titanium alloy electrode plate, power supply, and control system. The control system can adjust parameters such as voltage, current, and electrode polarity. Prepare a certain amount of 0.01%, 0.02%, 0.025% mM HCl and 0.05%, 0.1%, 0.15%, 0.20% NaCl solutions with tap water, electrolyze at 20V voltage, and measure the pH value and effective chlorine concentration of slightly acidic water electrolysis at different electrolysis times.

1.2 Time and location of disinfection test on breeding site

The experiment was conducted from October 28th to December 28th, 2009 at a breeding farm in Chongqing. The experiment was conducted in the nursing home of the pig farm, with a total of 30 sows and about 120 piglets in two rows and three aisles, manually cleared of feces. Daily disinfection uses povidone iodine twice a week.

1.3 Main experimental instruments and reagents

Water electrolysis generator, pH meter, oxidation-reduction potentiometer, effective chlorine analyzer, electric constant temperature incubator, pipette; Sodium chloride, hydrochloric acid, agar medium, etc.

1.4 Comparison Test of Disinfection Effect between Micro Acid Water Electrolysis and Chemical Disinfectant with Body

Before the experiment, clean the manure first, rinse the floor and pens of the pigsty with tap water, and start disinfection after the inside of the pigsty is dry. The same pig house was spray with three different disinfectants: slightly acidic water electrolysis (pH 6.25-6.53, oxidation-reduction potential ORP 887.5-924.8 mV, effective chlorine concentration 270 mg/l), strong disinfectant powder solution (1:4000 dilution, i.e. 0.25 g/l) and povidone iodine solution (1:250). The test interval of each disinfectant was one week, the amount of spray was 400 ml/m2, the disinfection time was 3:00 p.m., disinfection was once every four days, and the time of each spray was about 20 minutes. Samples were taken before and 0.5 h after disinfection, respectively, to investigate the three different disinfectant belt spray Sterilization effect of disinfection on air.

Comparative experiment on the local disinfection effect of 1.5 slightly acidic water electrolysis and chemical disinfectant on pigsty

Use slightly acidic water electrolysis (pH 6.23, ORP 892.5 mV, ACC 300 mg/l), 1:250 povidone iodine solution, and 1:4000 strong disinfectant powder solution to locally disinfect the floor, walls, and railings. The disinfection method is spraying, and it is advisable to keep the surface moist without standing water. Sampling should be taken 5 minutes before and after disinfection.

1.6 Sampling method

The air is sampled using natural settling method, with a sampling time of 3 minutes. The sampling points are arranged at the four corners of the pigsty (1 m away from the wall) and in the center, with 3 culture dishes placed at each position. The ground, fence, and wall were sampled using wiping method, with a sampling area of 1 × 2 cm2. A cotton swab was used to wipe back and forth 20 times, rotating the swab while wiping. Then, the swab head was broken and placed in a centrifuge tube containing 5 ml of buffer solution for storage. Each experiment was repeated 3 times. After sampling, place the culture dish in a 37oC constant temperature incubator and culture for 18-24 hours. Record the bacterial colony count in the culture dish. The calculation method for the total number of bacteria in the air is as follows:

Total bacterial count (cfu/m3)=50000 N/(A × T), where A is the area of the culture dish (cm2); T is the sampling time (min); N is the number of bacterial colonies per culture dish (cfu).

2. Results and Discussion

2.1 Effects of Electrolyte Concentration and Voltage on the Physical and Chemical Characteristics of Micro Acidic Water Electrolysis

The initial pH value of the electrolyte decreases with increasing concentration, which are 6.3, 5.48, and 4.52, respectively. During the electrolysis process, the pH value slowly increases. At the same electrolysis time, the pH value of the solution decreases with the increase of HCl concentration. After 30 minutes of electrolysis, the pH value of slightly acidic water electrolysis is about 6.0-6.59.

The initial effective chlorine concentration of HCl or NaCl solutions at various concentrations is 0. During the electrolysis process, the effective chlorine concentration rapidly increases, and the magnitude of the increase increases with the increase of electrolyte concentration. When the NaCl concentration is 0.15% and 0.20%, it reaches 192 and 248 mg/l respectively after 10 minutes of electrolysis.

2.2 Comparison of bactericidal effects of slightly acidic water electrolysis and chemical disinfectants on the air inside pig houses

The three disinfectants with body spray disinfection have certain germicidal effect on bacteria in the air. Micro acidic water electrolysis has the best bactericidal effect on air, reducing the total number of bacteria by 2.09 × 105 CFU/m3 before and after disinfection, with a bactericidal rate of 59.2%; The strong disinfectant solution was second, with a reduction of 1.54 × 105 CFU/m3 in total bacterial count and a sterilization rate of 48.7%. However, the povidone iodine solution had the worst sterilization effect, with a reduction of only 0.75 × 105 CFU/m3 in total bacterial count before and after disinfection and a sterilization rate of 25.9%.

2.3 Disinfection effect of slightly acidic water electrolysis and chemical disinfectants on the interior walls, fences, and floors of pigsties

Three disinfectants, namely slightly acidic water electrolysis, strong disinfectant powder solution, and povidone iodine solution, were presented for their local spray sterilization effects on pigsty walls, fences, and floors. Micro acidic water electrolysis and strong disinfectant powder have good sterilization effects on walls, fences, and floors, with a sterilization rate of 89.3-100%. The bactericidal effect of the three disinfectants on the ground, fence, and wall is gradually enhanced. Among them, the bactericidal effect of slightly acidic water electrolysis is the strongest, followed by strong disinfectant powder, while the bactericidal effect of povidone iodine solution is the weakest, with a bactericidal rate of only 14.3-83.3%.

3. Conclusion

The raw materials for slightly acidic water electrolysis are tap water and trace amounts of salt or dilute hydrochloric acid. The production and operation costs are low, the disinfection effect is good, and the cost of use is much lower than that of chemical disinfectants. Micro acidic water electrolysis has a pH value close to neutral, which is non corrosive to aquaculture facilities, has good stability, low cost, and avoids environmental pollution and harm to personnel caused by chlorine volatilization at low pH values. Compared with chemical disinfectants (Strong Disinfectant Powder and Povidone Iodine), slightly acidic water electrolysis (pH 6.25-6.63, ORP 887-924 mV and ACC 300 mg/l) has better germicidal efficacy for spray disinfection or local spray disinfection of pigpen belts, and the germicidal rate of walls, floors and fences reaches 91.4-100%. It can also be used for harmless disinfection of personnel, vehicles, etc. entering and leaving pig farms to ensure the healthy environment requirements for pig production. Therefore, the use of slightly acidic water electrolysis as a green and safe disinfectant for harmless disinfection in pig farms has good economic and environmental benefits.