The Top 8 Questions on Biofilm Control and Drain Cleaning Answered

In the “Battling with Biofilms: Know Your Enemy and Defeat them in Drains” webinar on May 12, 2022, Deb Smith from Vikan and Aidan Davey from ACO Building Drainage discussed the nature of biofilms and how to defeat them in a key biofilm stronghold: drains. During the webinar, we had so many great questions from our audience of over 1,600 registered attendees that we weren’t able to answer them all at the time. Below is a list of the top 8 questions answered by our Vikan and ACO Drainage hygiene experts. Some questions have been edited for brevity and clarity.

1. How often are drains cleaned in a food processing plant? Is it need-based, or is a certain frequency followed?

The frequency of drain cleaning in any food factory will depend on many things including:

• the type and condition of the drain
• the food type being produced
• the temperature of the production environment
• other relevant food safety factors

So, it is very much need-based, but overall, the frequency must be based on minimizing the risk to food safety. Consequently, if the drains are in a high-risk, ready-to-eat food production area where pathogens like Listeria monocytogenes are of concern, drain cleaning should be more frequent, than, for example, drains in a raw potato processing area.

2. What is the best solution for flush removal of biofilms from drainpipes that can't be accessed by brushes or other cleaning tools?

We don't think there is one-best-solution for the removal of biofilms from drainpipes other than a replacement. But replacement is costly and typically not feasible. So, before going down that route:

• Consider evacuating the pipe, and then do several consecutive treatments with a high-chlorinated alkaline cleaner with foam with at least a 10 min. dwell time.
• After that, ensure that using an appropriate drain maintainer chemical is part of the daily SSOP.
• Also, keep in mind you're most likely never going to completely get rid of biofilms deep in your drain, but you can prevent them.

Ideally, drainpipes should be easy to clean using brushes or other mechanical devices (such as pressure jet nozzles). If this is not possible, then you are dependent on fluid mechanics, with two principles apparent here:

(a) Need to clean before disinfection: Disinfection may kill microorganisms within the biofilm and may help its physical removal. However, disinfection is only possible if as much food debris has been removed from the drain as possible to provide cleaning access to the biofilm below. So, disinfection, such as with peracetic acid (PAA) or hypochlorous acid, should follow detergent application. As a caution: Do not use hypochlorous acid following acidic detergents.

(b) Assessing fluid velocities vs time: The slower the fluid flows down the drain, the longer the contact time will be required to achieve a similar level of cleaning. However, for disinfection, either a very slow flow or no flow (blocking the lower end of the drain) will extend contact time and thus disinfectant performance.

3. What is the best way to conduct a risk assessment on drains?

You are probably already familiar with conducting risk assessments as part of your food safety plan and environmental monitoring programs, using models like HACCP or HARPC, and the approach for drains will be exactly the same. So, among the key considerations, think about:

(a) Why are you doing the sanitation? – Is it to maintain general hygiene (food debris, levels of non-pathogenic/spoilage micro-organisms)? Is it to control specific hazards (pathogen bacteria, allergens, foreign bodies, chemicals), and, if so, which ones?

(b) What is the likelihood that these hazards will occur?

(c) What is the impact (severity) if hazards do occur?

(d) If the overall risk (likelihood x severity) is high, what controls can be put in place to lower this risk? This includes new hygienically designed drains; new floor-drain junctions; re-siting of drains, equipment, or processes; and use of validated sanitation methods, equipment, and frequencies, etc.

4. I am a food safety & inspection manager for a local health department. Specific to a food production plant that produces cooked as well as RTE foods, we are having a very specific Listeria strain issue that keeps occurring infrequently (at times years between issues). This happens regardless of the facility's cleaning, sanitizing, and environmental sampling/monitoring programs. Do you ever see this type of remediation-resistant issue, and do you have any "out of the box" ideas for potential reservoirs?

Remediation of resistant pathogen issues is certainly something that we have, and still do, come across regularly. These issues can present enormous challenges for the site, especially now with the use of genetic identification techniques, like whole genome sequencing, by agencies like the FDA. For Listeria, we have come across many common areas (like drains) and many uncommon hiding places. Some of the more uncommon ones include:

• Inside push button switches or behind push button switch covers on electric control panels
• Behind wall and door frame cladding
• Behind wall-mounted boards/signage
• Inside hollow equipment framework
• In the bearings of conveyor belts
• Inside trolley and tote wheels
• In the moisture traps of compressed air systems
• In the food-grade lubricants used
• In the door seals of refrigeration units
• On the skirts at the bottom of roller doors
• In the slide rails of sliding doors, etc.

5. What are the pros and cons of Channel Drains versus Pot Drains in RTE food manufacturing?

Below is a table summarizing the common advantages and disadvantages of the types of drains:

Channel Drain

Point Drain

Pros

• Can be used to convey water to a drainage point/slab penetration

• Can be used as a barrier to prevent contaminated surface water moving between zones

• Where short sharp flows are experienced, the flow can be attenuated or temporarily stored in the channel

Cons

• Larger surface area to be cleaned

• If not installed correctly, there can be issues with the gratings sitting properly, which could increase the risk of slips and trips

• Requires more excavation to install

Pros

• Ideal for capturing effluent from a specific outlet, such as oven condensate

• Faster to clean a smaller surface area

• Can be cheaper (but only if appropriate!)

Cons 

• Requires complex flooring that is sloped from all sides of the drain to allow for efficient drainage

• Properly trained site operatives may need to be paid to sweep water to the drain

• Less potential for debris collection (smaller baskets)

6. Do either of the subject matter experts have any tips for detection of biofilm that are not visible to the naked eye?

When it comes to biofilm detection there are several different approaches you can take. Which one you take should depend on what you are trying to achieve. For example,

(a) If you are looking to control the level of microorganisms on a surface and would like to know how many, or what type of organisms are present, you can use microbial swabbing. The swabs can be used to sample a surface and then be analyzed to give you the number of microorganisms present (usually expressed per unit surface area, e.g., numbers of microbes per square centimeter), or the number or presence/absence of a particular pathogen. Microbiological swabbing can provide you with quantitative/detailed information on the level/types of microbes present, however, it is expensive and takes time to get the results.

(b) If you are looking to see whether a surface is clean or dirty (even if it appears visibly clean), you can use ATP swabs. A high ATP result will tell you that lots of ‘organic dirt’ (microbes, biofilm, food, etc.) is present, a low result will indicate that it’s relatively clean. ATP swabbing is quick, easy, and relatively cheap to use. It is also widely used and accepted by the food industry. However, because you are looking for ATP (and not specifically microbes) it will depend on whether the ‘dirt’ you are looking for contains ATP in quantities representative of the dirt present. For example, ATP won’t detect viruses on a surface, as they don’t contain ATP.

(c) There are a few chemical spray methods available for biofilm detection, including:

• Biofinder, which works by detecting the catalase enzyme, which is found in many microorganisms, to react with hydrogen peroxide and release bubbles into a gel, and
• TBF 300s Biofilm Spray, which stains the polysaccharide ‘slime’ layer present in biofilms, showing their presence or absence visually.

Both detection technologies are quick, easy, and cost-effective to use as a way of detecting the presence of biofilms/monitoring cleaning. However, Biofinder may also pick up on catalase in some foods and give a false positive result, and neither give you any quantitative data (like microbial swabbing and ATP) or an idea of which microbes are present.

(d) Some auditors also use a UV flashlight, and UV scanning systems are also available, e.g., see video at: https://www.youtube.com/watch?v=_TVLATkrLAM. These systems may help visualize biofilms and allow targeted sanitation approaches.

7. What kind of cleaning method can remove biofilms most efficiently? There are various types of cleaning agents, but what kind of cleaning agent is said to be the most effective?

The most effective cleaning method to use for biofilm removal is mechanical action, i.e., scrubbing, wiping, use of pressured water, etc. However, the most effective approach to biofilm control is to use an appropriate combination of sanitation chemicals (detergents, disinfectants, sanitizers), at the appropriate temperature, together with the appropriate mechanical action, at an appropriate frequency.
The type of sanitation chemicals and mechanical action, and cleaning frequency and temperatures you choose will depend on many things, including, but not limited to:

• the type of food you are producing,
• the type of surface you are disinfecting,
• the standards/regulations you are trying to comply with

Our recommendation for the best course of action would be to speak to your local cleaning chemical supplier and get their advice. In our opinion, the best approach for remediation is to start with a product that has a high dose of surfactants and alkalinity for cleaning and then follow up with a registered biofilm disinfectant.

Remember, biofilms are filled with polysaccharides, proteins, fats, nucleic acids, and minerals, so another important point is to not expect biofilms to be removed after one cleaning. Remediation can take a while.

• First, you need to maximize the removal of the food soil that covers the biofilm in the drain. This is best achieved using the detergent selected for that soil removal on food processing equipment and the environment by the cleaning chemical supplier.
• At a second detergent stage, chlorinated alkaline detergents may be most effective.

8. What is the preferred water temperature for cleaning stainless steel drains?

The temperature of the water you use to clean your drains is important in relation to, at least, three things:

(a) the soils and debris you are trying to remove – If soils are protein-based, hot water could ‘cook’ them onto the surface of the drain and make them more difficult to remove. By contrast, if they are fatty, then hot water will aid removal;

(b) the chemicals you are using to remove soils – Sanitation chemical manufacturers develop their products to work optimally at a given temperature. If you are using a particular sanitation chemical for drain cleaning, you should use it with water at the suggested temperature; and

(c) the materials the drain is made from – Good drainage systems are constructed from materials that are suitably temperature and chemical-resistant. You should speak to your drain provider to find out the temperature range the materials in your drains are capable of withstanding.

Also note that:

-It is usually not necessary to use excessively high-temperature water for cleaning drains. ACO Building Draining recommends knowing the temperature, chemical concentration, and duration of the exposure from the sanitation chemical manufacturers so that ACO can advise on a suitable grade of stainless steel to be specified. Alternatively, by knowing these components of already-installed drains, ACO could suggest a maximum temperature.

-Deciding on the water temperature is also a tricky question. Obviously, the hotter the better, but higher water temperatures can decrease surface tension and aid water’s ability to remove soil. But we would say go as hot as your safety team allows you to, and within the chemical product’s specifications.

-Water temperature has a greater effect if you are trying to melt and remove fatty food residues e.g.,

• Lamb:            113-131˚F
• Beef & Pork:   104-113˚F
• Poultry:          >86˚F
• Butter:           >86˚F
• Mayonnaise:   >86˚F
• Egg & blood:   cold

Disclaimer: The responses given to these selected questions are the professional opinions of hygiene experts and are not necessarily endorsements of any of the products and services mentioned. Companies should conduct their own site-specific risk assessment and develop their own hazard controls as part of their food safety plan. For more information and support, please feel free to contact:

• Deb Smith, Vikan Global Hygiene Expert, for biofilm control and drain cleaning queries at dsmith@vikan.com
• Aidan Davey, ACO Building Drainage Regional Specification Manager, for drain selection and management queries at adavey@aco.co.uk