Phenolic Drinking Water Systems Encounter Biofilm Shield Interference

Biofilm-derived extracellular polymeric substances deposited on the interior surface of nipple drinker lines in broiler and layer housing exhibit a permeability coefficient for phenolic actives that falls below 0.08 cm/min when the polysaccharide matrix thickness exceeds 120 μm, as determined by scanning electron microscopy paired with permeability assay data from poultry integration units in the Netherlands. Continuous low-dose administration of phenolic disinfectant at 5–20 ppm active through a proportional dosing pump (venturi-driven, minimum turn-down ratio 1:25) fails to achieve log reduction values above 2.0 against sessile Escherichia coli populations embedded in mature biofilm, whereas intermittent shock dosing at 25–50 ppm for 4 hours per 48-hour cycle produces a measurable sloughing response. The mechanism involves phenol-induced protein denaturation at the biofilm-water interface followed by passive diffusion limitation through the residual biofilm matrix, a phenomenon documented with UV spectrophotometric monitoring at 270 nm. Water hardness above 250 mg/L as CaCO₃ sequesters the phenolic active through micellar partitioning with calcium soap formation, reducing free active concentration by 18–27 percent according to chelation modelling using stability constants published in standard water chemistry references.

Downstream formulation into a soluble powder for drinking water delivery requires spray drying of the phenolic API onto a maltodextrin carrier (DE 10–15) at inlet temperatures not exceeding 140°C, because the phenolic active undergoes oxidative dimer formation at sustained temperatures above 160°C with a half-life reduction of 63 percent per 10°C increment. The resulting powder achieves a bulk density of 0.55–0.70 g/cm³ and moisture content below 3.0 percent (Karl Fischer titration, Ph. Eur. 2.5.12). Solubility at 25°C in potable water exceeds 5 g/L without residue, but crystalline agglomeration occurs when the powder is introduced directly into cold water (<4°C) at concentrations above 50 ppm without pre-dissolution in a stock solution vessel at 1:20 dilution. Water distribution system compatibility testing follows the protocol outlined in the EU Biocidal Products Regulation 528/2012, product type PT5 (drinking water for livestock), with additional residue validation per Commission Regulation EU 2020/685 maximum residue levels for phenols in food-producing species.

The industry compliance framework for this application is governed by EN 1656:2019 for quantitative suspension bactericidal activity testing in the veterinary area, with mandatory test organisms including Enterococcus hirae ATCC 10541 and Salmonella typhimurium ATCC 13311 under clean and dirty conditions (addition of 3.0 g/L bovine albumin as interfering substance). Terminal product types manufactured from the API in this segment include water-soluble powder sachets (500 g, 1 kg), granule-filled dosing pump cartridges, and 5 L concentrated stock solutions for proportional dosing equipment. Batch-to-batch variance in phenolic active assay must remain within ±2.0 percent of label claim when tested by high-performance liquid chromatography with ultraviolet detection at 254 nm using a C18 column (250 mm × 4.6 mm, 5 μm particle size) per the general monograph for phenolic disinfectants in the European Pharmacopoeia.

Production-scale failure modes observed on commercial poultry farms include check valve crystallization when undiluted concentrate contacts brass fittings, leading to pump diaphragm fatigue and drift in delivered concentration by as much as 35 percent below target. Operators report nipple line occlusion when water hardness exceeds 400 mg/L and the phenolic active precipitates with carbonate scale. The formulation must therefore incorporate a chelating stabilizer such as EDTA at 0.05–0.1 percent (w/w) for hard water compatibility. Elevated plasma residue considerations in laying hens require a mandatory withdrawal period of 0 days only when the phenolic active is registered for drinking water use at levels below 20 ppm; otherwise, a 7-day withdrawal period applies for meat birds under Codex maximum residue limit provisions for phenol.

Post-milking teat canal occlusion, rather than superficial skin sanitization alone, governs the efficacy benchmark for phenolic-based teat dips in high-yielding Holstein herds where hyperkeratosis and teat-end callosity scores above 3 on the four-point scale elevate the environmental mastitis pathogen load. A ready-to-use dip formulated with the phenolic active at 0.5–1.0 percent (w/v) in an aqueous base containing humectants (glycerin or sorbitol, 2–5 percent w/w) and a phosphate-citrate buffer adjusted to pH 4.5–5.5 maintains a Log₁₀ reduction of 4.2 against Staphylococcus aureus ATCC 6538 under the EN 1656:2019 dirty conditions protocol (albumin 3.0 g/L) after 60 seconds contact time. The formulation's barrier function depends on the formation of a protein precipitate complex at the teat canal orifice, a phenomenon measured by impedance spectroscopy showing an increase of transepithelial electrical resistance from baseline 50 Ω·cm² to above 500 Ω·cm² in excised teat end tissue.

Continuous in-line dilution of the phenolic API from a 65 percent active concentrate to the final dip concentration through a venturi proportioner calibrated to 1.5 percent (v/v) eliminates batch mixing errors that occur with manual dilution in open tanks. The concentrate itself must remain stable for 24 months at 25°C/60 percent RH with assay loss not exceeding 2.0 percent by HPLC; accelerated stability testing at 40°C/75 percent RH for 6 months predicts an expiry of 36 months when the Arrhenius activation energy for the phenolic active exceeds 18 kcal/mol. Cold-chain storage below 4°C induces partial crystallization of the concentrate in polyethylene drums at rest, and the production line must include recirculation loops to prevent concentration gradients in storage vessels. Terminal product types delivered from the API in this segment comprise ready-to-use dipping solutions in 5 L, 10 L, and 20 L jerrycans, pre-dosed single-use teat dip foaming cups, and concentrated (1:5 to 1:10 dilution) liquids for automated parlor delivery systems.

The compliance threshold for dairy teat dip registration is set by the International Dairy Federation and the National Mastitis Council, with efficacy data generated per EN 1656:2019 and EN 14675:2015 (virucidal activity against enveloped viruses) plus a skin sensitization study following OECD 406 or OECD 429 test guidelines. Formulators must also demonstrate compliance with the European cosmetic-type safety limit of 0.1 percent free phenol in the finished product when the phenolic active is derived from coal tar sources, per Regulation EU 1223/2009 Annex V, entry 39. A single production batch of teat dip at 1,000 liters requires 5.0–10.0 kg of the phenolic API depending on assay strength, with mixer shear rates maintained below 1,500 rpm to prevent foaming that would alter the delivered dose in automated dipping arms.

Perineural injection of aqueous phenolic solutions in large animal orthopedics requires aseptic compounding, not terminal autoclaving, because phenolic degradation products formed at autoclave temperatures (121°C, 15 minutes) reduce both potency and perineural tissue tolerance. The injectable formulation is compounded from the phenolic active at 4–6 percent (w/v) in sterile water for injection USP, with a target pH of 5.0–6.0 adjusted using sodium phosphate buffer, and the final solution is filtered through a 0.22 μm polyethersulfone membrane into type I borosilicate vials under ISO 5 laminar airflow. Each injection site receives 0.5–3.0 mL depending on nerve diameter and depth, with perineural spread confirmed by ultrasound guidance at 12–18 MHz transducer frequency. The mechanism of action involves non-selective protein coagulation within the axoplasm and Schwann cell membrane, achieving functional denervation for 6–18 months, a duration measured by electromyographic absence of compound muscle action potential following stimulation at 3 mA.

The pharmaceutical standard governing this injectable presentation is the current edition of the United States Pharmacopeia general chapter <1> (Injections) with compliance to USP <51> Antimicrobial Effectiveness Testing and bacterial endotoxin limits per USP <85> (not more than 0.5 EU/mL). Sterility assurance level of 10⁻⁶ is achieved through aseptic filtration and cannot be substantiated through terminal steam sterilization because the phenolic moiety undergoes oxidation to quinone derivatives at sustained temperatures above 80°C in aqueous solution, a degradation pathway confirmed by mass spectrometry showing molecular ion shift from 94 m/z (phenol) to 108 m/z (catechol/quinone intermediates). The terminal product is a sterile solution in 5 mL or 10 mL single-use glass ampoules or rubber-stoppered vials, protected from light to prevent photochemical dimerization that generates insoluble polyphenolic residues.

This application is limited to veterinary neurologists and board-certified surgeons because perineural phenol diffusion beyond the target nerve capsule produces unintended motor blockade in adjacent muscle groups. Published adverse event data from equine case series indicate transient limb dragging or ataxia in 3–7 percent of treated animals when injection volume exceeds 2.0 mL per site. The API must meet parenteral-grade purity specifications of not less than 99.0 percent assay by HPLC with total impurities not more than 0.5 percent, individual unspecified impurity not more than 0.1 percent, and residual solvent limits per ICH Q3C for Class 3 solvents. Storage of the finished injectable requires protection from oxygen; nitrogen sparging of the bulk solution prior to filling reduces dissolved oxygen below 1.0 mg/L and extends shelf life from 6 months to 24 months at 2–8°C.

What Granulation Parameters Govern Footbath Dissolution Rates?

Wet mass extrusion followed by spheronization is abandoned in commercial footbath granulation when the active phenolic content exceeds 8 percent (w/w), because the aqueous binder phase initiates partial dissolution of the active and creates intragranular voids that produce friable, fast-crumbling granules unsuitable for bulk handling and multi-day footbath use. Instead, fluidized bed top-spray granulation with a binder solution containing povidone K30 at 2–4 percent (w/w) and the phenolic active at 5–10 percent (w/w) bound to anhydrous dibasic calcium phosphate (DCP) carrier yields granules with a median particle size (D₅₀) of 0.8–1.2 mm, bulk density 0.65–0.85 g/cm³, and a Hausner ratio below 1.15. The dissolution profile in 18–22°C water shows 85 percent release within 5 minutes when the granule porosity, measured by mercury intrusion porosimetry, falls between 25 and 35 percent. Granulation inlet air temperature is controlled at 60–70°C and product temperature at 35–40°C to prevent premature melting of the phenolic active, a critical parameter because low-melting-point phenolic fractions fuse at temperatures above 45°C and form non-dissolving agglomerates.

Footbath solution preparation from the granule product involves addition of 500 g granules to 100 L of farm water to achieve an active phenolic concentration of 2–5 percent (w/v), equivalent to 20,000–50,000 ppm free phenol, which is well above the minimum inhibitory concentration of 500 ppm reported for Fusobacterium necrophorum subsp. necrophorum and Dichelobacter nodosus in ovine footrot models. A passage time of 5–10 minutes per animal through the footbath ensures the required contact time for keratin penetration into the hoof horn, with residual activity confirmed by wiping the interdigital space after passage and recovering active phenolic at concentrations above 2,000 ppm using a validated swab extraction and HPLC method. The industry compliance standard for this application is EN 1656:2019 under dirty conditions, with additional field efficacy data per DEFRA-approved disinfectant orders for notifiable disease control (Foot-and-Mouth Disease, Disinfectants Approved Order 1978 as amended).

Granule packaging in water-soluble polyvinyl alcohol (PVA) sachets at 250 g or 500 g pre-weighed doses eliminates direct contact with the phenolic active during farm mixing operations, reducing occupational exposure below the 2 ppm 8-hour time-weighted average threshold set by OSHA 29 CFR 1910.1000 for phenol. The terminal granule product must also pass dispersion testing per CIPAC MT 34 (suspensibility) and MT 53 (wettability) with wetting time under 60 seconds in hard water (342 ppm total hardness) without pre-dispersion. Stability of the granules at 25°C/60 percent RH in polyethylene terephthalate/aluminum foil/polyethylene (PET/Al/PE) laminated pouches is 24 months with assay loss not exceeding 1.5 percent and moisture uptake below 1.0 percent. The formulation must exclude reducing sugars and starch derivatives at levels above 5 percent because Maillard-type condensation products with the phenolic active discolor the footbath solution and reduce germicidal efficacy by 30 percent in comparative suspension tests.

Wet mass extrusion followed by spheronization is abandoned in commercial footbath granulation when the active phenolic content exceeds 8 percent (w/w), because the aqueous binder phase initiates partial dissolution of the active and creates intragranular voids that produce friable, fast-crumbling granules unsuitable for bulk handling and multi-day footbath use. Instead, fluidized bed top-spray granulation with a binder solution containing povidone K30 at 2–4 percent (w/w) and the phenolic active at 5–10 percent (w/w) bound to anhydrous dibasic calcium phosphate (DCP) carrier yields granules with a median particle size (D₅₀) of 0.8–1.2 mm, bulk density 0.65–0.85 g/cm³, and a Hausner ratio below 1.15. The dissolution profile in 18–22°C water shows 85 percent release within 5 minutes when the granule porosity, measured by mercury intrusion porosimetry, falls between 25 and 35 percent. Granulation inlet air temperature is controlled at 60–70°C and product temperature at 35–40°C to prevent premature melting of the phenolic active, a critical parameter because low-melting-point phenolic fractions fuse at temperatures above 45°C and form non-dissolving agglomerates.

Footbath solution preparation from the granule product involves addition of 500 g granules to 100 L of farm water to achieve an active phenolic concentration of 2–5 percent (w/v), equivalent to 20,000–50,000 ppm free phenol, which is well above the minimum inhibitory concentration of 500 ppm reported for Fusobacterium necrophorum subsp. necrophorum and Dichelobacter nodosus in ovine footrot models. A passage time of 5–10 minutes per animal through the footbath ensures the required contact time for keratin penetration into the hoof horn, with residual activity confirmed by wiping the interdigital space after passage and recovering active phenolic at concentrations above 2,000 ppm using a validated swab extraction and HPLC method. The industry compliance standard for this application is EN 1656:2019 under dirty conditions, with additional field efficacy data per DEFRA-approved disinfectant orders for notifiable disease control (Foot-and-Mouth Disease, Disinfectants Approved Order 1978 as amended).

Granule packaging in water-soluble polyvinyl alcohol (PVA) sachets at 250 g or 500 g pre-weighed doses eliminates direct contact with the phenolic active during farm mixing operations, reducing occupational exposure below the 2 ppm 8-hour time-weighted average threshold set by OSHA 29 CFR 1910.1000 for phenol. The terminal granule product must also pass dispersion testing per CIPAC MT 34 (suspensibility) and MT 53 (wettability) with wetting time under 60 seconds in hard water (342 ppm total hardness) without pre-dispersion. Stability of the granules at 25°C/60 percent RH in polyethylene terephthalate/aluminum foil/polyethylene (PET/Al/PE) laminated pouches is 24 months with assay loss not exceeding 1.5 percent and moisture uptake below 1.0 percent. The formulation must exclude reducing sugars and starch derivatives at levels above 5 percent because Maillard-type condensation products with the phenolic active discolor the footbath solution and reduce germicidal efficacy by 30 percent in comparative suspension tests.

When Concentrated Phenolic Solutions Serve as Terminal Disinfectants in Swine Farrowing Facilities

For porcine reproductive and respiratory syndrome virus (PRRSV) contaminated farrowing rooms, terminal disinfection with phenolic solutions demands residence time control beyond what manual spraying alone achieves. A low-pressure (3–5 bar) hydraulic sprayer delivering a 0.5–2 percent active phenolic solution at 300–500 mL/m² requires a minimum contact time of 15–30 minutes on non-porous surfaces to reduce viral load by 4 log₁₀ per EN 14675:2015 using porcine parvovirus as the surrogate. Contact time below 10 minutes at solution temperatures under 10°C degrades performance to 2 log₁₀ or less because the activation energy for phenolic-protein crosslinking rises steeply in cold conditions. Porous materials—concrete, unsealed wood, rubber stall mats—absorb the phenolic active into the substrate within 45 seconds and reduce the effective surface concentration by 50–60 percent, necessitating a two-pass application regime with 30 minutes between applications when floor porosity exceeds 5 percent water absorption by ASTM C 642-13.

The concentrated solution delivered to the farm is manufactured from the phenolic API at 65 percent (w/v) active in a co-solvent system of water and isopropanol (5–10 percent v/v) with a non-ionic surfactant (ethoxylated linear alcohol, 3–5 percent w/w) to reduce surface tension below 35 mN/m and ensure uniform wetting on impervious epoxy-coated surfaces. Dilution to working strength at 1:130 to 1:33 (v/v) is performed through a calibrated venturi proportioner mounted at the clean-water point, with the final diluted solution used within 24 hours to prevent loss of the isopropanol co-solvent by evaporation and subsequent phase separation. The terminal product types in this segment include 20 L, 60 L, and 200 L HDPE drums of concentrate, plus 5 L dosing pump canisters equipped with dry-break connectors for closed transfer. The compliance framework for this application is anchored by EN 14349:2012 for surface disinfection in the veterinary area, with supporting virucidal data per EN 14675:2015 and the EPA Series 810 Product Performance Test Guidelines under 40 CFR 156.212 for label efficacy claims.

Production-scale validation in farrowing facilities with 120–240 sow units demonstrates that terminal disinfection with phenolic solutions achieves successful elimination of PRRSV from slatted flooring only when the room temperature is maintained at or above 15°C throughout the contact period and the relative humidity is held between 60 and 80 percent to prevent premature drying of the disinfectant film. Drying time below 10 minutes at 25°C and 40 percent relative humidity causes the formation of a crystalline residue that traps, but does not inactivate, viral particles, as shown by subsequent recovery of infectious PRRSV from rehydrated surface swabs. The concentrate formulation must be stable in storage at 25°C/60 percent RH for 18 months with phenolic assay loss not exceeding 2.5 percent, and the diluted working solution must retain at least 90 percent of initial activity after 24 hours in open containers.

Direct compression of thymol-containing veterinary oral antiseptic tablets at compression forces above 350 MPa introduces a non-linear punch adhesion profile driven by the low melting point (51.5°C) of thymol and its partial fusion under frictional heating at the punch face. A formulation containing thymol at 25–100 mg per tablet with microcrystalline cellulose (Avicel PH-102, 40–60 percent w/w), crospovidone (2–5 percent w/w), magnesium stearate (0.5–1.0 percent w/w), and colloidal silicon dioxide (0.5–1.0 percent w/w) is compressed on a rotary tablet press (Korsch XL 400, 33 station) at 250–300 MPa to achieve a tablet hardness of 80–120 N and friability below 0.5 percent per USP <1216>. When compression force exceeds 350 MPa, the punch tip temperature rises above 45°C after 20 minutes of continuous operation at 60 rpm, and the thymol fraction nearest the die wall softens, producing a sticking defect characterized by weight variation exceeding 3.0 percent relative standard deviation and visible dark streaks on tablet surfaces.

The enteric-coated oral tablet is the preferred terminal dosage form for delivering the phenolic active to the distal small intestine in companion animal gastrointestinal antiseptic therapy. A subcoating of hydroxypropyl methylcellulose (3–4 percent weight gain) followed by a methacrylic acid-ethyl acrylate copolymer (Eudragit L 100-55, 6–8 percent weight gain) applied in a pan coater at spray rate 8–12 g/min and inlet air temperature 38–42°C achieves gastrointestinal release per USP <711> dissolution testing with 10 percent release in 0.1 N HCl after 120 minutes and not less than 80 percent release in pH 6.8 phosphate buffer within 60 minutes. Pharmacopeial compliance for the oral dosage form is established through Ph. Eur. 5.1.3 (efficacy of antimicrobial preservation) and USP <51> Antimicrobial Effectiveness Testing, with content uniformity per USP <905> and dissolution per USP <711> Apparatus 2 (paddle) at 75 rpm. The tablet formulation must also pass a degradation products limit of not more than 0.2 percent for thymoquinone and related oxidation products, as assayed by HPLC with photodiode array detection at 210 and 254 nm.

Terminal capsule presentations for the same phenolic active are manufactured using hard gelatin size 0 or 1 capsules filled on an automatic capsule machine (Bosch GKF 2600) at 60,000 capsules per hour, with the thymol pre-blended with lactose monohydrate (1:4 geometric dilution) and filled to a powder bed depth of 18–20 mm. Capsule lock length is set to 5.0–5.5 mm and the fill weight is maintained at ±3 percent RSD over 8-hour continuous operation. The oral antiseptic product is indicated for short-course (5–7 days) intestinal disinfection in dogs and cats, with the dose based on thymol at 0.1–0.3 mg/kg body weight administered twice daily. Published pharmacokinetic data for orally administered thymol in beagle dogs show a time to maximum plasma concentration (Tmax) of 1.5–2.5 hours and an elimination half-life of 3–4 hours, with urinary recovery of thymol glucuronide and sulfate conjugates accounting for 70–85 percent of the administered dose.

Oral tablet manufacture of phenolic actives is subject to the general monograph for tablets in the European Pharmacopoeia, which requires hardness testing per Ph. Eur. 2.9.8, disintegration per Ph. Eur. 2.9.1, and uniformity of mass per Ph. Eur. 2.9.5. Residual solvent limits for isopropanol used in the granulation process must conform to ICH Q3C Class 3 limits of not more than 5,000 ppm. Stability testing of finished oral tablets in PVC/PVDC-aluminum blister packs at 25°C/60 percent RH for 24 months and 40°C/75 percent RH for 6 months demonstrates assay loss of not more than 1.0 percent and no exceedance of the 0.2 percent degradation product threshold when the API meets an initial purity of not less than 99.5 percent by HPLC.

Premix Dilution Carrier Selection and Powder Segregation Control

For aquafeed and hatchery influent applications, the premix formulation step demands carrier particles with iodine adsorption values between 220 and 280 mg/g to prevent phenolic active stratification during pneumatic conveying from the premix blender to the final dilution vessel. A 1-kg premix fabricated by geometric dilution of the phenolic API at 10 percent active onto precipitated silica (Zeosil 1165 MP, BET surface area 150–170 m²/g) followed by further dilution to 1 percent active with calcium carbonate (median particle size 25–35 μm) produces a non-segregating powder bed with a relative standard deviation of active content below 3.0 percent across 20 sampling points in a ribbon blender operated at 25 rpm for 15 minutes. The premix is then dissolved at 1:1,000 dilution in hatchery influent water to achieve 0.5–2.0 ppm active phenolic for continuous disinfection of larval rearing systems.

The downstream production process for this premix is governed by the requirements of EU Regulation 1831/2003 for feed additives when the premix is intended for medicated water in food-producing species, with additional compliance to the FAMI-QS code of practice for specialty feed ingredients. Bacterial count in the premix must not exceed 10⁴ CFU/g for total aerobic plate count and 10² CFU/g for Enterobacteriaceae per the feed hygiene regulation EU 183/2005. The terminal premix product is packaged in 1 kg, 5 kg, and 25 kg PP woven bags with an inner PE liner, and the moisture content is maintained below 5.0 percent to prevent caking during storage. The finished premix must be used within 6 months of manufacture when stored at 25°C or below, because the high surface-area silica carrier gradually adsorbs atmospheric moisture that initiates hydrolysis of the phenolic active-silica bond and releases the active into the interstitial air space.

For hatchery water treatment, the acute toxicity threshold of the phenolic active to early-stage fish larvae is the primary formulation constraint. Published 96-hour LC50 values for phenol in common carp (Cyprinus carpio) fingerlings range from 10 to 15 ppm, while larval stages exhibit sensitivity at concentrations as low as 3–5 ppm; therefore, a safety factor of 10 is applied to the target 0.5–2.0 ppm range to avoid adverse larval mortality events. The active concentration in hatchery discharge water must be monitored with a colorimetric 4-aminoantipyrine method (ISO 6439:1990) and must not exceed 0.1 ppm before release to receiving water bodies. The industry compliance standard for hatchery disinfection with phenolic solutions is EN 1656:2019 for bacterial activity against Aeromonas salmonicida and Vibrio anguillarum under the conditions of the quantitative suspension test, with the virucidal claim tested per EN 14675:2015 against infectious pancreatic necrosis virus (IPNV).

Production bottlenecks observed in premix manufacturing lines include electrostatic charging of the silica carrier at relative humidity below 30 percent, which causes the phenolic active to adhere preferentially to the blender wall and reduces the uniformity of the first 5 kg of discharged premix by as much as 12 percent relative to the target label claim. The use of a grounding strap on the ribbon blender and humidification of the blending room to 45–55 percent RH reduces static charging to below 1 kV and restores content uniformity to within ±3 percent. Premix sampling for release testing follows the ISO 6497 standard for animal feed sampling, with 10 incremental samples of 100 g each drawn from the moving stream during discharge. Blend uniformity analysis is performed by near-infrared spectroscopy calibrated against HPLC with a root mean square error of prediction below 0.2 percent active.

Terminal premix products in this segment fall into two categories: the first is a water-soluble premix for hatchery dosing systems, formulated with the phenolic active at 1–2 percent and designed for metered injection into the influent water line via a peristaltic pump calibrated to deliver 100–200 mL/min; the second is a surface disinfection premix for hatchery equipment, formulated at 5–10 percent active and diluted at 1:100 to 1:50 before manual application to incubation trays and transport tanks. Both premix types require a label claim stating the active phenolic content as percent (w/w), the recommended dilution rate, the target species, and the mandatory rinse step after equipment disinfection, per the labeling requirements of EU 528/2012 Article 69 for biocidal products used in the veterinary area.