Following Meat Industry Guide by Food Standards Agency:
Interpretation of results
Aerobic colony count (ACC) – the results of ACC tests can be used to assess the water quality
around the plant.
Guideline figures for acceptable ACC values are:
ACC at 22 oC after 72h – up to 100 per ml
ACC at 37 oC after 48h – up to 20 per ml
Regular samples from the same points on the system can indicate a developing contamination
problem. Any increase in counts above these guideline figures should be classified as a low level
Coliform bacteria (total coliforms) – expected levels are less than 1 per 100ml. Presence
should be considered as a low level positive and must be re-sampled – see ‘Follow up actions –
Low level positives’ in this section. If coliform bacteria are found at levels above 3 per 100 ml of
water, in two consecutive samples, or in more than 5% of samples taken within a year, this may
indicate contamination in the water distribution system, and urgent action must be taken – see
‘Follow up action - High level positives’ in this section.
E.coli – if E.coli is detected in water, this is evidence of contamination by animal or human faeces.
This is a serious food safety risk and urgent action must be taken – see ‘Follow up actions – High
level positives’ below.
Enterococci and Clostridium perfringens – are also an indication of faecal contamination and
urgent action must be taken – see ‘Follow up actions – High level positives’ in this section.
Chlorine – British Standards 12671: 2000 Chlorine dioxide – the combined concentration of
chlorine dioxide, chlorite and chlorate should not exceed 0.5mg litre as chlorine dioxide in the
water entering supply – see the ‘Introduction’ section in this chapter.
IV. Follow up actions
Follow up actions – Low level positives
Re-sample and test for all faecal indicators. If a further low level positive result is obtained, but
there is no evidence of faecal contamination, investigate the source of the problem.
Follow up actions – High level positives
Do not use the water outlet or tank from which the sample was taken (and associated outlets if
Meat Industry Guide
Page 17 | Chapter 3 – Water supply August 2015
necessary) until the contamination has been investigated and eliminated and satisfactory
microbiological results have been obtained from further samples taken at the point of entry, the
outlet from which the contaminated sample was taken and any other associated outlets.
Take the appropriate corrective action.
V. Corrective action
Corrective action – Water supply entering premises
If the water supply entering the premises becomes contaminated, it is the water supplier’s or local
authority’s responsibility to restore potable water quality. Follow their directions concerning water
use and product safety.
Corrective action – Contamination within premises
If the water supply becomes contaminated after entering the premises or non-potable water comes
into contact with food, take urgent corrective action to ensure food safety.
Corrective action may include:
isolating appropriate water outlets/tanks until satisfactory microbiological test results are
obtained (see ‘Follow up actions’ in this section)
stopping production where no potable supply can be provided
dealing with any product that has been contaminated, including removing it from the market if
establishing the underlying cause and what needs to be done to prevent similar contamination
incidents in the future, such as the installation of either a water filtration and chlorination
system or a water filter and ultra-violet sterilisation system
reviewing sampling and testing procedures
improving staff instructions and training