FAQs: Why Some Newburyport Residents May Notice Changes in Water Taste or Odor
March 13, 2026March 10, 2026
FAQs: Why Some Newburyport Residents May Notice Changes in Water Taste or Odor
This communication aims to expand upon recent information provided by the Newburyport Water Division regarding changes in taste, odor, or color of drinking water. These conditions are related to winter ice cover and seasonal mixing in the city’s drinking water reservoirs. While the taste, smell, or color can be unpleasant, the Water Division has confirmed that the water continues to meet all State and Federal drinking water standards.
FAQs: Geosmin in Reservoirs During Heavy Ice Cover & After Cyanobacteria Blooms
The taste and odor issues that some have experienced in recent weeks are due to a compound called geosmin. Geosmin spikes in reservoirs typically occur when cyanobacteria and actinobacteria produce this earthy-musty compound under certain conditions described below.
1. What is geosmin and why does it matter?
Geosmin is an earthy-musty odor compound produced by cyanobacteria (blue-green algae) and actinobacteria (filamentous bacteria in sediment). It is not harmful, but even tiny amounts can cause strong taste and odor issues in drinking water.
2. Why does geosmin increase during heavy ice cover?
Heavy or prolonged ice cover acts as a lid on the reservoir that creates conditions that favor geosmin production and accumulation. Ice cover prevents atmospheric oxygen exchange, which allows for low oxygen conditions to form that favor geosmin-producing actinobacteria that break down organic matter. The snow and ice cover keep geosmin-rich water from mixing and volatilizing, trapping it until temperatures increase and natural mixing and atmospheric exchange returns. Once the ice recedes and natural flow from Indian Hill to the Upper and Lower Artichoke Reservoirs is restored, the geosmin will be distributed throughout the water column or volatilize to the atmosphere, and the taste and odor issues will subside.
3. Why does geosmin spike after a cyanobacteria bloom?
Cyanobacteria blooms such as we experienced last summer at the Artichoke Reservoirs, can also cause geosmin events. Once the bloom collapses and begins to decay, cells can release stored geosmin into the water. Without evidence of an under-ice cyanobacteria bloom, it is likely that actinobacteria are now releasing geosmin into the water as they metabolize decaying cyanobacteria cells from last season.
4. How can we prevent or manage this issue in the future?
In 2025, the city treated the Artichoke reservoirs a record number of times with algaecide to reduce
cyanobacteria blooms and prevent toxins from entering our water supply. As droughts, high
temperatures, and high phosphorous loads from adjacent land uses and existing sediment
continue, it is very likely cyanobacteria blooms will become more prevalent. To prevent
cyanobacteria blooms and their resulting geosmin in the short-term, Newburyport’s Water Division
is obtaining permits to treat the reservoirs with alum, which binds phosphorus and prevents it from
feeding the cyanobacteria. An alum treatment should occur this spring. As opposed to algaecides,
which kill cyanobacteria but not geosmin, alum instead removes the food supply (phosphorus) that
feeds the cyanobacteria, thereby preventing blooms and the resulting release of geosmin.
In the long-term, the city is in the planning stages of constructing a new Water Treatment Plant
(WTP) that would include granular activated carbon (GAC) filters to remove PFAS for regulatory
compliance and also mitigate taste and odor concerns by filtering geosmin. This project has a 5-
year outlook, beginning with a 2-season pilot study which should begin this fall. The intent is to
utilize alum treatments in the interim to manage both cyanobacteria blooms and taste and odor
concerns while the WTP project progresses.
5. How does the Newburyport Water Division monitor geosmin events?
The Water Division monitors ice cover and reservoir levels daily during the winter. Because geosmin
is not a regulated compound that requires testing, recommended levels are not available from
regulatory agencies, and the Water Division does not normally test for geosmin. During the recent
changes in taste and odor, however, the Water Division opted to collect samples and have them
sent to a certified lab. Recent tests have shown geosmin levels between 250-315 ng/L (nanograms
per liter). Historically, levels above 10 ng/L have presented with reduced taste and odor quality.
FAQs: Manganese & Winter Ice Cover
The water appearance issues that some have experienced in recent weeks are due to manganese,
a naturally occurring mineral that can affect water color and visual quality. Spikes in manganese in
reservoirs typically occur when ice cover creates low-oxygen conditions. Typically, levels are
tested daily by the Water Division to ensure compliance with all state and federal regulations.
However, in recent weeks, the city has implemented a four-hour testing schedule for manganese in
order to adjust the pre-oxidant dosing. The Water Division can remove manganese by adjusting the
dose of potassium permanganate at the Lower Artichoke Pump Station. Potassium permanganate
oxidizes manganese to remove it from finished water. When a dose change is made at the raw
water station, the treatment plant does not see the effect of that adjustment for approximately four
hours, so the increased testing has allowed the Water Division to respond in real time to
adjustments.
State regulations advise that finished water should not exceed 0.3 mg/L for more than 10 days in
any calendar year for baby formula use. The City of Newburyport has never exceeded 0.3 mg/L.
Our current levels, from March 3 were 0.065 mg/L and levels from March 5 were 0.029 mg/L.
Should finished water levels ever exceed 0.3 mg/L, the city would notify the Massachusetts
Department of Environmental Protection and our local Board of Health. Should that occur, the city
would also issue a press release to notify the public.
1. Why does manganese increase during heavy ice cover?
During winter months, reservoirs often freeze. Heavy or prolonged ice cover acts as a lid on the
reservoir that prevents oxygen from entering the water. When this happens, bottom waters lose
oxygen and become anoxic. Under anoxic conditions, manganese in the sediments dissolve and
enter the water column as soluble manganese. Lack of mixing during snow and ice cover keeps the
anoxic layer stable, allowing manganese to build up. Once the ice recedes and the reservoirs can
mix and oxygenate once again, with natural flow from Indian Hill to the Upper and Lower Artichoke
Reservoirs, manganese will no longer be an issue.
2. Why are manganese levels closely monitored?
Exposure to manganese, especially to infants, can have associated health risks. State regulations
advise that finished water should not exceed 0.3 mg/L for more than 10 days in any calendar year.
This recommendation is protective for infants, who are more sensitive to manganese exposure, as
well as adults who can be affected by long-term exposure. The City of Newburyport’s Water
Division has been monitoring manganese levels daily to ensure levels are well below the
regulations. In addition to public health protection, when levels are kept below 0.05 mg/L, staining
and color issues are avoided.
3. How can we prevent or manage this issue in the future?
In the short term, Newburyport’s Water Division will continue to monitor the manganese
concentrations in surface water supplies and make appropriate adjustments to potassium
permanganate dose at the raw water pump station as needed.
In the longer term, the city is in the planning stages of constructing a new WTP that would include
an appropriately designed chemical feed system to treat for manganese with infrastructure at the
Water Treatment Plant to effectively respond to the changing concentrations rather than relying on
operations at the remote raw water pump station.
