Proponents of EM claim that adding effective organisms to wastewater can facilitate reduction in organic load and pathogen removal, leading to significant improvements in effluent quality. They also claim benefits relating to the rate of sludge build-up and odor reduction. One source claims that EM can reduce hydrogen sulphide and ammonia production.[3] Their reasoning is that EM mixtures contain natural’ organisms that prevail over the rather less ‘natural’ organisms that would otherwise dominate conditions in the treatment unit, whether this be a septic tank or some form of aerobic treatment. They even claim that by overcoming the effects of ‘unnatural’ substances such as bleach and other disinfectants, addition of EM allows septic tanks and other treatment systems to function in conditions that would otherwise have resulted in their becoming ‘dead’ and non-functional.
One short note claims that EM microorganisms contain various organic acids due to the presence of lactic acid bacteria. These secrete organic acids, enzymes antioxidants, and metallic chelates thus create an antioxidant environment, which assists in the enhancement of solid-liquid separation, which is the foundation for cleaning water.[13] The authors of the note provide no explanation of how this works.
However, the findings from various studies around the world indicate that:
There is no reliable evidence that addition of EM solutions to wastewater prior to treatment has a significant effect on pathogen concentrations.
The evidence on the effect of EM solutions on settleability of solids and reduction in effluent BOD and SS is mixed. Under some circumstances, it appears that adding EM can have some effect on both BOD and SS concentrations but the effect is not large and is not proven.
The available evidence suggests that any lasting effect of EM is dependent on regular application of EM organisms combined with good maintenance of the treatment technology. This will require (a) a reliable supply chain for the EM material and (b) management systems that ensure that the EM material is added regularly and on schedule.
While it is possible that EM techniques can lead to some improvement in effluent quality, it is unlikely that the improvement obtained will be sufficient to allow effluent uses that would not have been possible if EM had not been added. In particular, it seems that any claim that EM use can make otherwise ‘unsafe’ effluents from primary and enhanced primary treatment process ‘safe’ is unlikely to be justified.