Abstract
Wastewater from a municipal wastewater treatment plant (Mexico) was treated by a coagulation-flocculation using natural gums. The residual water was characterized in terms of organic load, and biological contaminants, i.e. total Coliforms (TC), fecal Coliforms (FC) and helminth eggs (HE). The sample has values of 2.8 × 107 MPN/100 ml, 8.48 × 106 MPN/100 ml and 470 HE/L is regarded to TC, FC and HH, respectively. The HE identified in the wastewaters were Diphyllobothrium latum, Ascaris lumbricoides, Hymenolepis nana and Toxocara canis. From several gums, Hydroxypropyl triammonium chloride guar gum (HPTAC-guar) was selected as the most adequate coagulant-flocculant for the class of municipal wastewater (MWW). A diminution of 82% for TC, 94% for FC and 99% for HE was obtained. Besides, the reduction of chemical oxygen demand (COD) and turbidity removals were 46% and 39% respectively. The natural gum mixed with Ca(OH)2, obtained removals of 52% for TC, 100% for HE, 47% for COD and 30% for turbidity.
Highlights
Recent studies of two more important Mexico City wastewater flows demonstrated that municipal wastewater (MWW) is having a medium-weak charge with strong bacteriological characteristics, high alkalinity and mineral content [1]
The characterization of the physicochemical and microbiological MWW is shown in Table 2
Regarding the pH value, MMW is slightly acid. In this analysis the chemical oxygen demand (COD) value for MWW is twice the COD value reported for others wastewaters from effluents generated in Mexico City [1]
Summary
Recent studies of two more important Mexico City wastewater flows demonstrated that MWW is having a medium-weak charge with strong bacteriological characteristics, high alkalinity and mineral content [1]. Bacteriological factors and global epidemiological studies on the use of wastewater for agricultural purposes, in Latin American countries, have shown a great public health risk by gastrointestinal diseases such as diarrhea, caused by the presence of viruses, bacteria, protozoa and helminth eggs [2]. The microbial pathogen concentrations are different depending of many factors such as the month in the year, the specific zone, etc. Determining the number of different microbial pathogens in a sample of water or wastewater is essential to prevent or control a feasible epidemic [3].
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