Both the multi-tube fermentation method and the enzyme substrate method are used for quantitative determination of coliform bacteria in drinking water.However,the following characteristics distinguish the two methods:

①Different inoculum volumes.The multi-tube fermentation method uses 5515 mL of water sample,while the enzyme substrate method uses 100 mL.

②Different detection ranges.The multi-tube fermentation method covers 2–1600(M PN/100 mL),while the enzyme substrate method ranges from 110 to 20015(M PN/100 mL).

③Method sensitivity differs.The multi-tube fermentation method detects 2 cfu per 100 mL sample;the enzyme substrate method detects 1 cfu per 100 mL sample.

④Method steps differ.The multi-tube fermentation method involves multi-step determination,being time-consuming and labor-intensive;the enzyme substrate method employs one-step determination,saving time and effort.

⑤Time requirements differ.The multi-tube fermentation method requires 24 hours for reporting results on negative water samples and 72 hours for positive samples;the enzyme substrate method provides results within 24 hours for both negative and positive samples.

⑥Method costs vary.The multi-tube fermentation method can utilize semi-finished or self-prepared culture media,resulting in low testing costs.Currently,commercially available culture media and disposable consumables for primary fermentation tests have been developed domestically.However,the requirement for confirmatory testing of positive samples limits the widespread adoption of these commercial reagents.The enzyme substrate method relies on commercial reagents,currently supplied only by foreign manufacturers,leading to higher testing costs.This method is more widely used in economically developed eastern regions.