Pollution in the Yarqon River
Written by Yonathan Raz, the Yarqon River Authority’s ecologist.
The pollution incident in the Yarqon River that led to the extinction of living things in a section, about 20 km in length, of the river whose overall length is 27.5 km, did not begin as an incident connected directly to the Yarqon River.
A fire, which broke out at an office furniture factory in the Neve Naaman industrial zone in Hod HaSharon, spread to the storage area for raw materials used in the production of cleaning materials, including detergents, at the “Sano” plant. Some 1,500 cubic meters of water were used to extinguish the blaze, which completely destroyed the furniture factory while in the Sano factory tanks containing about 160 tons of detergents and raw materials were engulfed by the flames. As soon as a warning about the fire was received, the Yarqon River Authority erected earthen barriers in the drainage channels, into which the fluids were supposed to flow thereby preventing them from flowing into the Yarqon. As the incident ended, the fluids polluted by the detergents were supposed to be cleared out of the channel and treated in keeping with the regulations of the Ministry of Environmental Protection and thereby prevent the pollution of the environment.
What actually happened, for reasons which have yet to be determined, a large quantity of fluids polluted with high concentrations of detergents and waste produced during the burning of the materials in the factories, flowed into the wastewater collection system and a short time later reached the wastewater treatment plant jointly operated by Kfar Saba and Hod HaSharon. The detergents caused the wastewater treatment process to breakdown and as a result detergents and effluents which remained virtually untreated, flowed into the Yarqon. It should be noted that effluents from the plant are one of the Yarqon’s water sources and the plant is currently undergoing upgrading to ensure that the effluents’ quality suits the water allowed to flow into the rivers.
At this stage in the incident the damage was already unavoidable. The toxic waters flowed into the Yarqon, and then for about a week afterwards inferior quality effluents were allowed to flow until the treatment process in the installation was restored in full. The fluids flowed in the Yarqon from the area around the installation for a period of about 4 days and an evaluation of the situation indicated that all living things and the food chain in the aquatic ecosystem were destroyed.
Along the entire 20 km of the polluted river, dead fish sank initially to the bottom of the river bed before rising up to float on the water surface two days later as the decomposition processes proceeded. For seven days the Yarqon River Authority cleaned up the river and during the cleaning operation 106 tons of dead fish were gathered up and removed. The majority of the mass of dead fish in the river’s middle (sweet water) section was catfish while in the river’s saline section the fish collected were mainly mullet. Additionally, St.Peter’s fish, eels and various other kinds of sea fish were also collected.
The damage to the river did not result only from the toxicity of the detergents themselves but was also due to the fall in the concentration of dissolved oxygen in the river water. The normal oxygen concentration in the river ranges form 3 to 6 milligrams per liter. During the course of the pollution incident, the oxygen concentration was close to zero and those living creatures who perhaps managed to survive the poisoning by detergents were left with no chance of survival.
Following the pollution of the river all the aquatic birds, which populate the river regularly and wintering birds such as cormorants and coots (fulica atra) deserted the river and its banks. A large number of these aquatic birds moved to the lakes adjoining park Ganei Yehoshua but several dozens of them failed to do so, either because of a lack of orientation or owing to the fact that they “erroneously” entered the river’s water, which had been polluted by the detergents, and so lost their fatty cover which protects their feathers from the water. These birds suffered from dampness, cold, hunger and even thirst during the pollution incident. The employees of the Yarqon River Authority and a volunteer caught several injured birds and transferred them to a sailing lake to wash off the soap and help them recover.
The chain reaction to the pollution incident was not confined to the Yarqon River alone but spread to the residential areas adjoining the Yarqon, where following the fish mortality in the Yarqon, families of hungry mongooses who normally fed off the living things in the river suddenly appeared after being forced to seek food elsewhere and now competed with stray cats over other sources of food such as domestic garbage cans. Additional animals such as jungle cats, jackals and foxes would probably also be detrimentally affected following the disappearance of these food sources. As yet we do not know what happened to the adult Nile soft-shelled turtles and the young soft-shelled turtles, which had been returned to the Yarqon River or broke out of their shells during the past year, in those stretches of the river which had been poisoned.
As the incident started and the extent of the pollution was realized, the Yarqon River Authority put its emergency procedure into action and instructed the Mekorot Water Company to increase the flow of drinking water (spring water) into the Yarqon from 270 m3 per hour to 1,600 m3 per hour. The increased water flow continued for 13 days during which an additional 405,000 m3 of drinking water was allowed to flow into the Yarqon. Once the pollution in the Yarqon was over monitoring of the mosquitoes was implemented and the mosquito larvae which began to reproduce in the river were eradicated because the pollution had harmed the population of natural predators.
The process of the Yarqon’s rehabilitation in those stretches of the river damaged in this incident will probably take several years. Initially it will be the protozoa, invertebrates and worms living in the water which will reproduce considerably because their natural predators will be missing from the river. During the following stages diverse schools of fish will spread and populate the river depending on the water quality and the availability of appropriate food. The Yarqon River Authority in cooperation with various bodies involved in nature protection and with researchers from academic institutions, will assess the situation and repopulate the river with the living creatures, which had became extinct in the river as a result of the pollution, all depending on the conditions of the habitats and the progress of the plans for the Yarqon’s rehabilitation.
The Yarqon River will be rehabilitated and all of us are charged with the task of preventing a repeat of a pollution incident.