It has been known for decades that the point-source discharges from wastewater treatment plants are an easy source of pollution to address. The technology to significantly reduce the nitrate and phosphate concentrations in the wastewater stream has existed for decades, and is constantly being improved. Wastewater treatment plants were originally designed to remove pathogens and offensive odors from contact with the public. Only subsequently was the need to address nutrient pollution addressed seriously by sanitary engineers. Wastewater treatment plants, like septic systems, return the nutrients used to grow the food we eat back to the environment.
Why haven’t nutrient reduction technologies been installed decades ago? The fundamental reason is that people have not been willing to pay for the increased service, and government (EPA) has not mandated that they do so. This is a classic example of EPA protecting the Economy and not the Environment. It is important to understand that reducing nutrient release from the pipes of wastewater treatment plants will have an immediate effect in improving water quality. Nutrients are returned to the environment from wastewater facilities in three forms: 1) as gasses like ammonia and NOx’s (all pollutants), and diatomic nitrogen, 2) dissolved in the wastewater, and 3) in the sludge.
The Blue Plains wastewater facility of the DC Water and Sewer Authority (www.dcwasa.com) purports to “Serve the public and protect the environment.” Each day the plant discharges 300 million gallons of water containing 6 mg Nitrogen/liter, or about 7 tons of N. It generates about 1000 (wet) tons of sludge each day, lime-stabilizes it, and land applies it. Assuming a moisture content of the sludge of about 80% and that it contains about 2% N on a dry weight basis, each day about 4 tons of N are land-applied, at least 45% of which does not benefit crop production. If the 365,000 tons/year were landfilled at a cost of $30/ton for tip fees, the cost to the 2,200,000 customers would be about $11,000,000. Each customer would see their annual bill increase by no more than $5, the equivalent of two bags of junk food, each year. Obviously, using the waste as biofuel (generating methane and combusting/pyrolizing the residue) would eliminate the cost of landfill tip fees, and is economic today if the cost of the pollution to society is taken into account.
The often-touted economic benefit of land application of sewage sludge for farmers must be balanced against the alternatives. In Virginia, according to a Joint Legislative Audit and Review Commission (JLARC) Report #89 (jlarc.state.va.us), municipal sewage sludge is spread on 50,000 acres annually, out of millions of acres farmed in Virginia. The vast majority of Virginia farms are obviously profitable without using sewage sludge in lieu of chemical fertilizer. The average saving, about $56/acre, means the total saving for farmers, state wide, is about $3,000,000 each year. The recreational value of Chesapeake Bay and citizen’s “willingness to pay” to improve water quality vastly exceeds $3 million each year by any estimate (e. g., the article by R. Hanmer in the October 2004 Bay Journal – www.bayjournal.org.) In Virginia alone, banning the land application of municipal sewage sludge would keep about 4.4 million pounds of nitrogen from being disposed on fields to no benefit of crops. As reported in the February 2007 Bay Journal, the cost of upgrading the Blue Plains wastewater treatment plant to eliminate a similar amount of nitrogen discharge will be between $500 million and $1 billion! The economics are crystal clear. The cheapest way to increase agricultural fertilization efficiency and eliminate a massive source of pollution of Chesapeake Bay is to ban the land application of animal waste. In the case of sewage sludge, the increased cost would have only a minor effect on a very few farmers, and would require an inconsequential increase in wastewater bills even if the waste were landfilled.
Storm water also discharges pollutants to the Bay, especially in the case of Combined Sewage Overflow where sewage mixes with storm water after heavy rains. Blue Plains releases, directly to the Bay, the equivalent of about 7 million gallons per day of Combined Sewage Overflow. The amount of nitrogen and phosphorus (and fecal coliform bacteria) in the discharge is not advertised. Pollution by “urban infrastructure” includes both wastewater treatment plants and storm water discharge. There is no doubt that we must eventually upgrade our aging infrastructure. Given our current economic situation, why not mandate upgrades now, beginning with the most egregious sources of pollution, and create badly needed jobs at the same time. Politicians wring their hands and complain that “all we need is more money to improve water quality.” Money derives from the people (or from government printing presses, with well known consequences) so “let the polluter pay.” Municipal bonds provide safe investments and spread the economic pain as equitably as possible over a long term. To improve water quality we must reduce nutrient pollution by changing our behavior and not doing everything as cheaply as possible. There is no alternative to upgrading urban infrastructure and increasing agricultural fertilization efficiency if Chesapeake Bay water quality is to improve. We either spend money to fix the problems or live with what we’ve got.