3 / 2023-09-29 23:18:09

Restoration of Water Quality with Emphasis on Removing Organochlorine Pesticides and Eutrophic Conditions in Rivers of Venezuela Applying In Situ and Ex Situ Techniques. Cases: Chirgua River, Paito River, Guacara River, Ereigüe River and Tucutunemo River

coupled bioreactors;,phytoremediation system;,river restoration techniques,sequencing batch reactor;,upflow anaerobic filters;,Vetiveria zizanioides

This work deals with an approach for the water quality restoration with emphasis on the removal of organochlorine pesticides (OCPs) and eutrophic conditions in rivers of Carabobo and Aragua states, Venezuela. The presence of OCPs and eutrophic conditions have caused influence on the management of the central-regional aqueduct, as a source of water supply for human consumption (4 million people) and industrial production in the states of Carabobo, Cojedes and Aragua, Venezuela. The treatments for the removal of OCPs and eutrophic conditions will consist to test in situ bioremediation technique associated to phytoremediation through Vetiveria zizanioides (VZ) species and ex situ bioremediation technique supported on coupled bioreactors, Sequencing Batch Reactor (SBR) followed by an Upflow Anaerobic Filter in Three Separate Stages (UAF-3SS). Five rivers are involved known as Chirgua, Paito Guacara, Ereigüe and Tucutunemo, whose waters have been classified as hypereutrophic, and containing organochlorine pesticides (OCPs). As a sample, for Tucutunemo River, OCPs included to DDT (dichlorodiphenyltrichloroethane) and its isomers and DRINs (Aldrin, Endrin and Dieldrin) dissolved in water and sorbed on sediments, which were measured during the dry and rainy seasons in the period 2013 to 2016, in three monitoring stations distributed in a reach of 15 km.  The results indicated that p.p’-DDT concentration dissolved in water was increased up to 10 times from rainy to dry seasons, indicating that a permanent use is being carried out by farmers in the agricultural activity development. Steady concentrations of the DDT isomers (e.g. p.p'-DDD and p.p´-DDE) and Aldrin isomers (e.g. Dieldrin) demonstrated that the anaerobic and aerobic biodegradation processes occurred along the river and between climatic seasons. At experimental scale, VZ hydroponic system developed over a period of six months for the removal of nutrients demonstrated moderately low to high removal efficiencies. With respect coupled bioreactors, each bioreactor has been experimentally tested, demonstrating  satisfactory performance in Chemical Oxygen Demand (COD) removal from industrial wastewater containing recalcitrant and inhibitory substances (46-98%), which was estimated in the influent ranging from 3,500 to 5,500 mg/L, evidencing that coupling of bioreactors might lead to an effluent COD complying with environmental regulations.