Biosolids in Flint

The Flint debacle is still spinning my wheels. I had this thought early on: might the release of lead through the Flint water system be traceable to the wastewater and biosolids in Flint?  What do you think?

I have had a long-standing interest in lead.  In my role as an advocate for recycling Philadelphia’s biosolids, I felt defensive about lead concentrations in our two sources of biosolids, as our concentration was double the national average.  I took solace in the notion that the metals of an urban environment were being safely sequestered through the biosolids, and emplacement safely in  soil,  as benign a final disposition as could be hoped.

I undertook a big-picture look at lead in 2004 to wrap my arms around the movement of lead through Philadelphia’s environment. I find today this exercise relevant to the Flint issue.  I estimated the system-wide loading of lead from Philadelphia’s 2.3 million customers was less than 2,000 pounds annually. This lead is carried to the waste water plants in 1,000 billion pounds of water.  Back-of-the-envelope calculation says the average total concentration of lead in waste water is 2 parts per billion, pretty small.  The lead received for treatment and subsequently trapped in Philadelphia’s biosolids was from all sources. Because Philadelphia’s is largely a combined storm/sanitary system, these sources include erosion of urban soils, street dirt derived from brakes and tires, precipitated sediment from drinking water filtration, as well as the lead from corroded service lines and home plumbing fixtures. 

Is 2,000 pounds of lead sequestered annually in biosolids signal a problem for a city as large as Philadelphia?  Allocating this load of lead to different sources is very difficult, and the risk to human health from this lead is very difficult. The highest concentration of lead in the water supply system is “first flush” when taps are opened in the morning, after a night of corroding the faucets.  This flush is only occasionally the source of water for drinking or cooking, as less than 1% of water flushed to our sewers is used for drinking or cooking.  About one-third Philadelphia’s annual waste water flow is storm water, with all the street dirt it carries, but customers are not in close contact with this loading. Much of the lead exposure to children in Philadelphia is not from water, but from un-vegetated urban soils and legacy lead-based paint, and very little of this reaches the biosolids.

National standards for lead in drinking water are not easy to wrap your head around.  Current press reports remind us that ‘zero’ is the standard for drinking water lead. But the concentration of concern is 15 ug/L. This is a level above which water agencies need to take action if more than 10% of sampled households exceed that concentration.  In such a protocol, a few sampled homes can exceed the 15 ug/L level, and a water system still need not take “action.”  In the national program, corrosion control is presumed at the outset, and any required “action” would be above and beyond that.  Flint had no corrosion control; this was the central SNAFU when exceedances in its tap sampling occurred and no action was taken.

Getting back to biosolids as an indicator of lead in the environment, what can biosolids data show us?  For Philadelphia in 2004, our biosolids never varied enough to put me worryingly close to the Table 3 Pollutant Concentration.  The data told me that no large unreported sources of lead to our wastewater “shed” were looming to be discovered.  When I made the very conservative estimate that all of the lead carried to our biosolids was from drinking water, even then the water at the tap would be less than 2 ug/L, well below action levels. Further, even if a few taps deliver water far higher than 2 ug/L, most taps would be lower than that concentration.

The US EPA had data to show that lead was not a major issue from a national view. EPA conducted the National Sewage Sludge Survey of 1989, followed by the “Targeted” survey of 2002, with an expanded analysis of persistent organic compounds.  National data from a representative sample of treatment plants yielded a national mean lead concentration of 74 mg/Kg with a standard deviation 79 mg/Kg; the median is 44 mg/Kg.  I take this to mean that a significantly higher concentration occurred in a few sampled plants. An example of that would be Philadelphia’s biosolids, with its 150 mg/Kg lead level hitting the up-side of the standard deviation. Nevertheless, the EPA  Statistical Report that accompanied the Targeted NSSS projected that no treatment plants would exceed the Part 503 Ceiling Concentration limits.

Is the EPA biosolids survey relevant today? I reviewed recent reports from several state regulators on biosolids quality.  Biosolids lead concentrations are all low in these reports, about 10 percent of the range represented by Part 503 Table 1 Ceiling Concentration standard of 840 mg/Kg and the Table 3 Pollutant Concentrations standard of 300 mg/Kg.  For example, the annual mean lead concentration for all reporting utilities in Florida (2013) was 21 mg/Kg; for Michigan (2009) 31 mg/Kg; for New Jersey (2013) 33mg/Kg; and for New York (2009) 90 mg/Kg (likely the impact of NYC, which is similar to Philadelphia in lead concentrations).

Overall, the data tells me that, nationwide, water and wastewater systems do not show a hidden, dangerous risk of community lead exposure from drinking water.  If Philadelphia’s calculations are representative, based on national biosolids data, the nation’s drinking water systems are far lower than 1 ppb lead in the water supplies put to drains.

Getting back to the opening question, is there anything to learn about lead exposures in Flint, Michigan, by looking at lead in its biosolids?

I called Rob Case, City of Flint Water Pollution Control Division Supervisor. Rob is a career waste water professional who came up the ranks through the labs.  Lab data is at his fingertips, which is true for the biosolids produced by his plant, even though it is landfilled. Rob is concerned about what he regards is widespread mis-representations of risks from lead in his city’s water distribution system. He recommends the statement issued by the President of Flint’s Kittering University for a balanced discussion.

The bottom line is that Flint’s biosolids reveal no recent increases to lead loadings. In 2006, when Flint’s water source was Lake Huron and was treated for corrosion inhibition, the annual average lead in Flint’s biosolids was 59 mg/Kg, and the maximum monthly concentration was 96 mg/Kg.  In 2015, with Flint’s water supply coming from the more aggressive Flint River source and with the distribution system unprotected by corrosion control, the annual average lead concentration in Flint biosolids was 54 mg/Kg and the highest monthly value of 83 mg/kg. These numbers are essentially identical before and after the change in water source, and both are well in line with national and state averages.

It is highly likely that the story of lead exposures in Flint is much more complicated and nuanced than you would gather from the media stories. Scientifically valid evaluations tend to suffer when politics and media attention join the fray.

My concern with Flint story is that “government” apparently failed to act properly under the Safe Drinking Water Act and the Copper and Lead Rule in its operations and particularly in its lack of response to data.  One consequence is the adequacy of current regulatory approaches to protecting customers is being broadly questioned, as in the NY Times article  Unsafe Lead Levels in Tap Water Not Limited to Flint. This questioning may very well be a good thing, if environmental issues and our commitment to infrastructure can achieve greater saliency in today’s political debates. Sadly, the questioning may instead feed the popular cultural myth that government can’t be trusted and thereby undermine efforts to attract money for infrastructure

The risk illuminated in Flint is the kind of risk that we in the biosolids profession shoulder. We collect much data about biosolids and we put our programs at risk when we pay no attention to that data. I have seen careless reporting of biosolids data, as when values are reported to state regulators in units of mg/Kg when the lab sheets were in units of ug/Kg. I have seen mindless reporting, as when a Part 503 biosolids reports disclosed a sudden ten-fold spike in cadmium concentration, right to the Table 1 limit, with no explanation.  I have seen lab sheets with detection levels higher than regulatory standards, an apparent consequence of a mistaken test protocol.

I have seen too much stupid stuff.  Stupid stuff can get us in trouble. Flint is a reminder of that.  So, if you haven’t looked closely at your last lab report on biosolids quality, do it now. Think Flint, take action, and get the lead out.