Metals in wastewater and effluents

Tests for metals concentrations at various stages of treatment are performed for the association through an outside laboratory. These tests are performed on the raw sewage, effluent and sludge.

The concentration of metals in effluent is a key issue in light of the very high concentration of metals found in the seabed of the Kishon Bay, some of which are toxic and hazardous. A direct relationship between metals and morbidity among the users of the bay and divers in the area has not yet been clarified. However, the association feels that it is important to emphasize that the treatment facility is not a contributor of hazardous metals during accidental discharge of effluents from the facility into the Kishon River.

The source of metals in raw sewage is usually industrial wastewater discharged into the sewage collectors in the cities in the association's service area.

The wastewater treatment facility is designed to treat organic materials and nitrogen in the wastewater and is not designed to treat metals in the raw sewage.
Some of these metals may undergo chemical reactions during treatment or bind with larger molecules, both organic and inorganic. Furthermore, some of these metals may undergo physical processes of adsorption, settlement and accumulation in sludge.

It is important to emphasize that high concentrations of metals in raw sewage may harm treatment processes of the wastewater, which are based primarily on bacterial action that is sensitive to the presence of heavy metals.

Analyses of metals in the wastewater entering the treatment facility show no deviations from concentrations permitted according to municipal ordinances, whether based on a monthly average or an annual average. However, numerous deviations were found from the municipal standard for discharge of industrial waste into sewage collectors in tests performed on wastewater at various plants.

Results of analyses of heavy metals in facility effluents (see the attached table) show that the concentration of metals in these effluents is very low since most of the metals reaching the treatment facility in the raw sewage are absorbed into the sludge during treatment and are removed with the sludge.

Metals considered as having high risk such as mercury, cadmium, arsenic and silver were found in all measurements to be at levels lower than the threshold for their detection. Other toxic metals such as copper, chromium, lead and nickel were found in very low concentrations in the effluents.

Based on the metals data in the effluents (see the table below), it can be concluded that the treatment facility does not contribute heavy metals to the waters of the Kishon River, and from it into Haifa Bay.
Metals in treatment facility effluents (annual average in mg/L)
 
 
2009 2010 2011 Metals
0 0 0 Ag Silver
0 0 0 As Arsenic
0 0 0 Cd Cadmium
0 0 0 Cr Chromium
0.004 0.001 0.016 Cu Copper
0 0 0 Hg Mercury
0.009 0.005 0.008 Ni Nickel
0.005 0 0 Pb Lead
0.083 0.058 0.091 Zn Zinc