05-09-2012, 10:40 AM
EFFECTIVE MICROORGANISMS (EM) AND WASTEWATER SYSTEMS
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Abstract
The use of effective microorganisms (EM) for reducing volumes of sewage sludge has
often been suggested as feasible in either wastewater treatment plants or on-site
wastewater treatment systems such as septic tanks. The organisms are supposed to
eliminate the volumes of sludge produced, with the benefits of reduced sludge handling,
and consequently lower costs and decreased impacts upon the environment. This project
aimed to test the hypothesis that EM is beneficial in reducing sludge volumes. Two
areas of experimentation were undertaken, one at a controlled experiment at the Coffs
Harbour Wastewater Treatment Plant (CHWTP) and a second on five domestic septic
tanks in the Armidale-Dumaresq area (northern NSW).
Results from CHWTP showed a significant decrease in pH levels with increased EM
dose, improved settlement of the sludge, but a significant increase in BOD5. There was a
significantly higher level of solids in the treated tanks compared to the control. The lack
of consistency between the tank treatments with respect to quality and quantity of
sludge remained an issue. The septic tanks indicated a pattern of similar conditions
following a final application, suggesting domination by a particular type of
microorganism. However, there was no reduction in suspended solids content in the
effluent. It is concluded that there were not sufficient changes to sludge volume
(CHWTP) or suspended solids (septic tanks) to indicate a clear benefit from the use of
EM in wastewater.
Introduction
A major problem facing municipalities throughout the world is the treatment, disposal and/or
recycling of sewage sludge. Generally sludge from municipal waste consists mainly of
biodegradable organic materials with a significant amount of inorganic matter (Elliot 1986).
However, sludge exhibits wide variations in the physical, chemical and biological properties
(Colin et al. 1988; Bruce 1990). At the present time, there are a number of methods being
used to dispose of sewage sludge from disposal to landfill to land application.
Although there are many methods used, there are numerous concerns raised regarding the
presence of constituents including heavy metals, pathogens and other toxic substances. This
requires the selection of the correct disposal method focussing on efficient and
environmentally safe disposal. New technologies are being produced to assist in the treatment
and disposal of sewage sludge, conforming to strict environmental regulations. One of these
new technologies being proposed is the use of Effective Microorganisms (EM).
The technology of Effective Microorganisms (EM) was developed during the 1970’s at the
University of Ryukyus, Okinawa, Japan (Sangakkara 2002). Studies have suggested that EM
may have a number of applications, including agriculture, livestock, gardening and
landscaping, composting, bioremediation, cleaning septic tanks, algal control and household
uses (EM Technology 1998).
Testing of Effective Microorganisms
Literature suggests Effective Microorganisms significantly reduce volumes of sewage sludge
produced while removing the associated odours. Therefore, this tends to suggest an
improvement in the digestibility of sludge and other solids in septic tanks and therefore the
efficacy of septic systems. The main hypothesis of this project is that the application of EM
will result in a trend towards a reduction in the level of solids, and hence a reduction in
sewage sludge. The reduction of solids in a septic tank are best monitored in the short term,
by changes to the total suspended solids (TSS), total dissolved solids (TDS) and total solids
(TS) in the effluent discharging from the septic tank
Effective Microorganisms (EM)
EM is available in a dormant state and requires activation before application. Activation
involves the addition of 7 L of chlorine free water and 1.5 kg of brown sugar to 3 L of
dormant EM one week prior to application.
These ingredients were mixed together in either a 15 L or 20 L container and stored in an area
with minimal temperature fluctuations. A major influence on the survival of microorganisms
is the temperature of their environment, with significant temperature fluctuations impacting
upon their survival. The pH is also a determining factor. It was indicated that the pH of the
EM should be approximately 4.5 (Newton, G. 2002 pers. comm.).
Septic Tank Experiment
Five septic tanks in the Armidale-Dumaresq region were treated and sampled to determine the
effect of the EM upon the suspended solid content of the wastewater. These septic tanks were
chosen for their similarity in size and wastes, and relative closeness for ease of monitoring.
The only difference between the tanks was the number of persons served by the single tank.
Two further tanks were discarded due to the need for pumping out (restricting sampling).
An initial dose of 6 L of activated EM was applied to the septic tank at the inlet inspection
port. Three litres were then added one week later, with 350 mL doses applied once each week
after that for the next three weeks. A total of 10 L over the four weeks.
It has been suggested that activated EM may be applied to the toilet or any other drain leading
to the tank. However, for ease of sampling and addition, the activated EM was applied
directly into the septic tank at the inlet port. The activated EM should also be added a number
of days prior to washing of clothes due to large influxes of water and temperature
fluctuations. However, this was not a factor that could be controlled. Hence the addition of
activated EM was undertaken on the same day each week (Saturday). Samples were taken
from the outlet pipe of each septic tank once per week before application and were analysed
for pH, electrical conductivity (EC), total alkalinity, total solids (TS), total suspended solids
(TSS) and total dissolved solids (TDS). This testing was undertaken as outlined in (APHA
1995) and methods used are given in Table 1.
Conclusions
This experiment was undertaken to determine if the application of Effective Microorganisms
(EM) would decrease the volumes of sewage sludge produced in on-site wastewater treatment
systems (septic tanks). There was no appreciable reduction in the suspended solids content of
the septic tanks, with minimal influences on pH, alkalinity and electrical conductivity during
the application of EM. It was observed following final application of EM that a decreasing
trend in pH, EC, alkalinity, TS and TDS began. It was also observed that a phenomenon of
common conditions was created following a two-week period with no application of EM. This
was attributed to the creation of optimal conditions for EM survival and hence may result in
further decreases of suspended solids content.