Physicochemical and biological combined treatment applied to a food industry wastewater for reuse.

The aim of this study was to improve the wastewater treatment plant (WWTP) efficiency of a food industry. Despite the anaerobic-aerobic treatment, the efficiency of the plant is poor because of the high pollutants load derived mainly from the use of disinfectants and sanitizers. These cleaning products are used in the production process. In order to achieve the main goal of the study, the pollutants load reduction was targeted and a physicochemical treatment was added for that purpose. For this effort, the tests were divided in three parts. The first consisted of performing coagulation-flocculation laboratory tests to select the best chemical reagent for reduction of the high load of pollutants present in the influent. The evaluated compounds were ferric chloride, aluminum sulphate, hydroxychloride of aluminum (AHC) and polyaluminum sulphate (PAS). The second was a pilot plant study in which physicochemical and biological treatment werecombined. Finally processes were verified in the WWTP characterizing the effluent and evaluating the process for compliance with standards for reuse water. The results showed that the best coagulant was hidroxichloride of aluminium. Improving the relationship Chemical Oxygen Demand/ Biological Oxygen Demand (COD/BOD(5)) of 0.27 to 0.45 and getting a dose of 1 to 5 mg L(- 1) in the laboratory, which improved to make scaling to plant 0.5 to 2 mg L(- 1) with efficiencies removal of contaminants 98% for COD, 95% for BOD(5), 99% for O&G, to 99% for TSS and helminth eggs were not detect. The wastewater was characterized with cyclic voltammetry and the sludge produced with AHC was analyzed by scanning electron microscopy (SEM) and energy-dispersion spectroscopy (EDS).

Toxicity assessment of a complex industrial wastewater using aquatic and terrestrial bioassays Daphnia pulex and Lactuca sativa.

Aquatic and terrestrial bioassays were used to assess toxicity at several stages in an industrial wastewater treatment plant that processes 400 L/s from a complex influent formed by wastewater from 135 industries. Daphnia pulex and Lactuca sativa were used to assess and compare toxicity between the influent wastewater and effluent wastewater from an activated sludge process, and compare their relationship with physicochemical parameters of Biological Oxygen Demand (BOD); Chemical Oxygen Demand (COD); Total Suspended Solids (TSS); total Nitrogen (N (N-total)), and ammonia Nitrogen (N (N - NH3)). Samples from the primary clarifiers (PC), mix liquor stage (ML) and secondary clarifiers (SC) were processed using physicochemical and bioassay test. Toxicity results with Daphnia pulex showed decreased mean values of acute Toxic Units (a.T.U.) between PC (2.1 a.T.U.) and SC (1,25 a.T.U.). Lactuca sativa showed high values of toxicity between PC and SC (3.37 and 3.32 a.T.U. respectively). Some samples exhibited higher toxicity values at the effluent stage (SC) than the influent stage (PC). The highest correlations of physicochemical properties with toxicity were obtained with COD and nitrogen compounds in effluent samples (SC), but not with influent samples (PC).