Study looking at water data from 1980 to 2011 shows improvement in some parts of the state.
Some pollution that causes algae blooms in rivers, streams and other waterways has declined in parts of New Jersey over three decades, according to a report released Monday.
But the results of the study looking at water data from 1980 to 2011 show a mixed bag for North Jersey's rivers.
The amount of nitrates, a common water contaminant that forms from sources like fertilizers and human excrement, has been increasing in Bergen and Passaic counties' waterways. Two other pollutants – nitrogen and phosphorus – that also come from waste and fertilizers is decreasing.
The Hackensack River was one of the few rivers whose nitrates concentrations decreased over the 31-year period. Levels of phosphorus and nitrogen remained steady.
The Passaic River at Two Bridges in Wayne showed a decrease in nitrogen concentrations but an increase for nitrates. Phosphorus remained level.
The Ramapo River showed nitrates increasing over the years. There was no trend for the other two pollutants.
The Passaic River at Little Falls showed a downward trend for nitrogen and phosphorus but an upward trend for nitrates.
The Saddle River had upward trends for nitrates and no trend for the other two.
State Department of Environmental Protection officials said improvements to wastewater treatment plants and efforts to curb runoff have led to the decrease in pollution levels around the state.
The study focused exclusively on three of the most common contaminants that come from suburban communities and plague waterways. It did not examine industrial waste, bacteria, pesticides and other pollution found in New Jersey's waters.
Excessive levels of phosphorus and nitrogen can kill fish and degrade water quality by exacerbating algae growth and depleting oxygen. The most common sources are discharges from water-treatment plants; runoff containing residential and agricultural fertilizers; animal wastes; and old septic systems.
The study comes as the state is considering whether to allow more residential development in the most protected areas of the New Jersey Highlands. The proposal would allow 1,145 more septic systems in the Highlands – a plan that environmentalists say would degrade streams, lakes and reservoirs in a region that produces drinking water for millions. Driving the push is a report by the U.S. Geological Survey that said the region could sustain more potential nitrate pollution without substantially affecting water quality. The DEP is still responding to comments received about the plan, an agency spokesman said Monday.
Jeff Tittel, director of the New Jersey Sierra Club, expressed concern that the polluted water is likely getting into drinking water supplies. The North Jersey District Water Supply Commission has been pumping about 140 million gallons a day into the Wanaque Reservoir from the Passaic River at Two Bridges, where nitrate levels have been rising. High levels of nitrates can pose a health risk, especially for infants and the elderly, if consumed regularly.
But the most recent water quality report from the operators of the Wanaque Reservoir shows nitrates at less than 1 part per million. The federal drinking water standard for nitrates is under 10 parts per million.
Runoff continues to be a persistent problem.