Ananth Kashibhatla
30 January 2023
Environmental Microbiology
Extra Credit Seminar – January 23 – Dr. Fahrenfeld
In Dr. Fahrenfeld;s seminar titled “Microplastics in Our Waters: Sources, Fate, and
Biofilms”, she takes an in-depth look at how humans are adversely affecting the contents we put
out in our waters affect our ecosystem and environment. She starts her seminar with talking
about having a lack of circular economy for plastics is hurting us more than we think. Recycling
is heavily further emphasized and many marine life organisms such as fish end up mistaking
plastic debris in the ocean for food. Next, Dr. Fahrenfeld delves into the specifics of these
plastics, particularly called microplastics, which are manmade polymers that are less than 5 mm
of diameter. The two types are primary microplastics, which are manufactured in small sizes and
secondary microplastics, which are derived from larger plastic, either photophysical or
mechanical degradation. Most of the deadly plastics that are deadly for organisms are these types
of plastics or microplastics. Then, in the conceptual model of fate and transport, several sources
contribute to this microplastic accumulation, for example but not limited to atmospheric
deposition, land-based riverine sources, at-sea pollution, and UV & oxidative weathering. Over
time, you end up accumulating these wastes, which end up becoming harmful to the organisms
that reside in these waters. Furthermore, the lack of evidence of these ecological impacts is the
reason why many people are not taking this issue seriously. However, California is the first state
that is taking these issues seriously and is the first state to regulate microplastics, especially in
the context of drinking water. In the Raritan-Hudson estuary case study, it was found that a lot of
these microplastics are prevalent in the river plume that originally came from the coastal ocean,
with the sediments accumulating and becoming a biohazard for peoples’ drinking waters. We can
study these effects by measuring the concentrations found in sources such as wastewater influent
+ effluent, stormwater and zooplankton in low and high flows via nets. Dr. Fahrenfeld goes on to
then talk about different concentrations of biowastes in the context of the aforementioned low
and high lows with small and large MP. In addition, different polymer types were also found in
these wastes such as other plastic, vinyl copolymer, polyester, polystyrene, polypropylene,
rubber and polyethylene, with the majority of the uses extending to packaging,
building/construction, automotive, electrical/electronic, and others. Then, Dr. Fahrenfeld also
points out a graphic that shows the different types of polymers in the context of its source, such
as wastewater effluent, wastewater influent, wastewater solids and compost. Another method that
was used to study the prevalence of microplastics is fate, which is the uptake into zooplankton
sources. Different methods are devised to study microplastic concentrations in these
microorganisms. Nitric digestion is also another point that was mentioned where you could use
these methods to “digest” these wastes and PE2, PMMA-1 and PC concentrations were taken
into account for this study. The sources that you can find these wastes are usually in the
wastewater and stormwater sources. As such, it was shown that wastewater treatment plants are
actually effective in removing these microplastics. Different biofilms also exist, such as glass
microbeads, large polyethylene, small polyethylene, large polystyrene, and small polystyrene; we
compared these concentrations in WW Influent and Raritan River sources. An effective method
to disinfect these wastes is the use of peracetic acid but it was found that it’s only effective when
the LDPE is approximately equivalent to Wood.