Summary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

1 This summary focuses on measurements made in MWRA wastewater flows at Deer

Island , and MWRA environmental monitoring. In Massachusetts, most mercury (about 90%) in the rivers, lakes and oceans comes from atmospheric deposition and about 10% from “point sou rces” like treatment plants.

I. DITP Wastewater:

There have been statistically significant decreases in both concentration and total loadings of mercury to DITP since the beginning of the decade. Effluent concentrations and loadings have also decreased

. (Some but not all of the decrease in effluent concentration can be explained by the high flows in 2005 and 2006

. )

Mercury Concentrations: Influent

0 .1 .2 .3 .4 .5Mercury concentration (ug/L)

2000 2001 2002 2003 2004 2005 2006 South System Influent North System Influent Error Bars: 95% Confidence Interval

Figure 1 Changes in influent mercury concentration since 2000

. Influent concentration measurements are highly variabl e, but are substantially lower in 2006 than in previous years.Summary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

2 Mercury Concentrations: Effluent

Average Effluent Mercury Concentration

0.000 0.005 0.010 0.015 0.020 0.025 0.030

1999 2000 2001 2002 2003 2004 2005 2006 2007Mercury (ug/g)

Mercury Loadings:

Mercury Loadings (pounds/day) from DITP Effluent and Biosolids pellets: 1999-2006 (2006 data through August)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1999 2000 2001 2002 2003 2004 2005 2006 Effluent Pellets Figure 2 Mean annual e ffluent concentration of mercury at DITP since September

2000 has dropped from 0.026 ug/L in 2002 to 0.01 ug/L in 2006 (through October)

. ( The means were estimated using Helsel’s Regression on Order Statistics which assumes a lognormal distribution and handles the non

- detects appropriately

. )

Figure 3 Total mercury loadings in DITP effluent and biosolids pellets. Because flows affect

concent ration and are highly variable from year to year, mercury loadings measurements give a better idea of the total amount of mercury entering and leaving the plant. Effluent +biosolids can be a reasonable surrogate for influent.Summary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

3 [ Note: Our NPDES reporting d ata (based on fiscal year) do not show exactly the same trend in influent loadings suggested by the effluent + pellet data (Figure 4) , this is likely due to the variation in flows. Sampling error for influent is also relatively high.

DITP Influent:

In F Y 02, influent loadings to DITP were 0.55 lbs/day In FY 06, influent loadings to DITP were 0.43 lbs/day

DITP Effluent:

E ffluent loads also decreased, from about 0.1 lb/day to <0.05 lb/day ]

0 .1 .2 .3 .4 .5 .6 .7 .8Average Mercury Load (lbs/d)

2001 2002 2003 2004 2005 2006 Effluent Influent Mercury Loadings at Deer Island Treatment Plant

Fiscal Year

Figure 4 Influent and effluent mercury loadings to DITP FY01

- FY06Summary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

4 II. Biosolids Pellets :

Wastewater treatment removes the merc ury from the water to the sludge. Therefore it is important to look at mercury in the solids removed. [Technical note: for mercury measurements in the pellets, there are discrepancies in results between the contract lab now doing the work and MWRA’s DLS re sults: the contract lab is giving results about 25% lower than are obtained in

- house. It is not clear what the cause is, split samples are still being analyzed. Therefore, although the pellet concentrations are likely lower than in previous years, we are n ot yet certain of the amount of decrease.]

Concentration: Figure 4 shows that the c oncentration in biosolids pellets from Fore River has significantly decreased over the past 5.5 years : from 4.6 mg/kg to 1.9 mg/kg

.

Figure 5 Change in concentration of mercury in MWRA

biosolids pellets since 2000, (data are through June, 2006)

. 0 1 2 3 4 5 6Mervury (mg/Kg)

2000 2001 2002 2003 2004 2005 2006 Mercury concentrations in sludge pellets

Error Bars: 95% Confidence IntervalSummary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

5 Mercury Loadings in MWRA Biosolids Pellets

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007Pounds/Day

Figure 6 Loadings of mercury in biosolids have dropped by more

than 50% since 1999.

III. Environmental M ercury: Sediments, Mussels, Lobster, Flounder

Sediments:

Boston Harbor Sediments: NOAA sediment quality guidelines for mercury sugges t that at less than 0.15ug/g, adverse effects are rare, while above 0.71 ug/g adve rse effects are often observed. In Boston Harbor in 1994, 7 out of 12 stations had average mercury levels exceeding

0.71 ug/g . In 2002, 4 out of 12 stations exceeded 0.71.

In the Outer Harbor, average mercury levels have remained relatively stable since 1994,

at 0.5

- 0.8 ug/g (ppm) dry weight. In the Inner Harbor which is relatively more affected by runoff, there has been a decrease in sediment mercury from about 0.75 ug/g in 20 01 to about 0.6 ug/g in 2004.

Massachusetts Bay There has been little change in mercury levels either near the MWRA outfall or far from the outfall over the monitoring period (since 1992). In the nearfield (sites nearest the outfall) average mercury lev els have remained at 0.2

- 0.3 ug/g from 1992

- 2004; in the farfield mercury levels have stayed at about 0.15

- 0.25 ug/g.

Fish and Shellfish Comparison to Regulatory S tandards:

EPA recommends that states develop site

- specific standards for water quality ba sed on estimated human fish consumption from the site. ( Massachusetts has not done this yet.) EPA’s “default” water quality standard for methyl

- mercury is 0.3 mg/kg (parts perSummary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

6 thousand) wet weight. Flounder and lobster tissue 1 from Boston Harbor and the ou tfall

site have t otal mercury (likely th e same as methyl mercury) ranging from 0.07 to 0.17 parts per million in lobster and flounder, well below the default standard. Mussels deployed at the outfall site and in Boston Harbor are much lower, 0.0122 to 0.0173 parts per million. These levels are also well below the FDA action level of 1 .0 ppm

.

Fish and Shellfish Patterns in Mercury C oncentration in Over T ime:

There have been no significant changes in mercury concentration in lobster, flounder and

musse ls measured in Boston Harbor and at MWRA’s outfall site in Massachusetts Bay when data before and after the outfall came on line are compared. This reflects that most mercury entering the harbor and bay comes from atmospheric sources which have not change d substantially.

Summary:

Our best estimates are that that mercury entering DITP has decreased about 50% since 2000, from 0.76 lbs/day to 0.35 lbs/day. Concentrations of mercury in DITP effluent and biosolids pellets have both decreased.

In 1988, EPA ’s Supplemental Environmental Impact Study for DITP and the outfall predicted that the plant would discharge 216 kg mercury annually after full build

- out. However, over the past 5 years, DITP has averaged a discharge of 12 kg mercury annually

— 95% less than the assumptions upon which the plant was planned and built.

The relatively low loading of mercury from DITP is consistent with the negligible changes measured in sediments fish and shellfish in the area near the outfall discharge. Meanwhile, Boston Harb or sediments in the inner harbor may be beginning to show small decreases in mercury , as it is removed by natural processes.

1 Mercury bioaccumulates, which means that higher level predatory f ish l ike tuna accumulate more than animals like lobster and flounder, that consume prey lower in the “food chain.” These types of fish which

are found in Massachusetts waters are also highly migratory.Summary of MWRA mercury mon itoring data A. Rex November 2 7 , 2006

7 More detail on fish and shellfish 2

Mussels:

Mussels deployed in Boston Harbor : There have been no significant changes in mer cury levels in mussels deployed either near the previous outfall site in Boston Harbor or in the Inner Harbor. Levels have remained at 0.13 to 0.18 ug/g dry weight. ( A slight increase since 2000 is due to increased “background ” concentrations in the musse ls before they were deployed

. )

Flounder caught in Boston Harbor:

Overal l , there has been no significant trend in mercury levels in flounder in Boston

Harbor since 1998; the average has been about 0.3

- 0.4 ug/g dry weight.

Lobster caught in Boston Harbor:

Overal l , there has been no significant trend in mercury levels in lobster in Boston Harbor

since 1998; the average has been about 0.8

- 0.9 ug/g dry weight.

Massachusetts Bay:

Mussels deployed in near the outfall: At the outfall site, average mercury con centrations in mussels have increased from 0.09 parts per million to 0.15 parts per million. However, this increase is due to increased “background” concentrations in the mussels before they were deployed

.

Flounder caught near the outfall:

Overal l , there has been no significant trend in mercury levels in flounder caught near the

outfall since 1998. The mean as been 0.4

- 0.5 ug/g dry weight. However, in 2003

- 2004 mercury in flounder at the outfall site was relatively elevated at about 0.6

- 0.7 ug/g.

Lobst er caught near the outfall:

Overal l , there has been no significant trend in mercury levels in lobster caught near the

outfall since 1998. The mean as been about 0.9

- 1.0 ug/g dry weight.

2 MWRA analyzes both wet weight and dry weight merc ury. Dry weight represents the concentration of mercury without interference by the variable amount of water in a sample, so MWRA looks at spatial and temporal trends based on dry weight. However FDA and EPA standards for human consumption are based

on wet weight.