Application of Composite Pre-Polymerized Coagulants for the Treatment of High-Strength Industrial Wastewaters

Abstract

The aim of this study was the investigation of alternative pre-polymerized coagulants for the treatment of high-strength industrial wastewaters, such as those created by tanneries, or by yeast production industries. The novel inorganic composite coagulant examined in this study (as well as variations of it) was denoted as PSiFAC1.5-10-15. The contribution of a typical polyelectrolyte to improve the effectiveness of the coagulation/flocculation (C/F) process was additionally studied, either by adding it separately (i.e., as a flocculant aid) or by co-polymerizing it within the structure of inorganic coagulant (denoted as PAPEFAC1.5-10-15). It was found that the PSiFAC1.5:10:15 coagulant, either with or without the addition of polyelectrolyte, can provide better efficiency for the C/F process than the conventional coagulants. For example, the addition of 80 mg Al/L in yeast production wastewater samples resulted in a 56% reduction of COD, 40% of turbidity, and 43% of phosphates, regarding the pre-treated anaerobically wastewater samples and reduced by an extra 22%, 14%, and 38% for the pre-treated anaerobically plus aerobically wastewater samples, respectively. The residual aluminum concentration in the treated wastewaters was found to be below the legislation limit of 200 μg Al/L. The characterization of coagulants showed the relatively higher Al13 content of 51% and 43% for the cases of PSiFAC1.5-10-15 and PAPEFAC1.5-10-15, respectively, accompanied by the high zeta-potential measurements (50.5 and 39.5 mV).

Advanced Oxidation Processes and Biotechnological Alternatives for the Treatment of Tannery Wastewater

“…Tannery wastewater is the product of a transformation process from organic matter to non-degradable matter, which requires the addition of compounds and additives that allow such transformation, generating in turn waste highly polluting not only for human health, but also for the environment [ 34 ]. These wastewaters have as main characteristics a dark brown color, a characteristic odor due to the presence of volatile organic compounds, organic and inorganic carbon, phosphorus (P), nitrogen compounds (N) [ 9 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], fats and other highly polluting compounds at certain concentrations, such as chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS), chlorides, sulfates and heavy metals such as Zinc (Zn) and chromium (Cr), among other things [ 37 , 43 , 44 , 45 , 46 ]. Goswami and Mazumder [ 47 ] reported a typical characterization of tannery wastewater, where COD concentrations were observed between 500 and 11,500 mg*L −1 , total Kjeldahl nitrogen (TKN)—200–550 mg*L −1 , observing that the highest fraction is available as ammonia nitrogen (NH 3 –N), total chromium concentrations (Cr(VI) and Cr(III)) in a range of 5–140 mg*L −1 , slow biodegradability due to the content of biodegradable compounds is less than 50% and very high total dissolved solids (TDS) compared to total suspended solids (TSS).…”

“…Goswami and Mazumder [ 47 ] reported a typical characterization of tannery wastewater, where COD concentrations were observed between 500 and 11,500 mg*L −1 , total Kjeldahl nitrogen (TKN)—200–550 mg*L −1 , observing that the highest fraction is available as ammonia nitrogen (NH 3 –N), total chromium concentrations (Cr(VI) and Cr(III)) in a range of 5–140 mg*L −1 , slow biodegradability due to the content of biodegradable compounds is less than 50% and very high total dissolved solids (TDS) compared to total suspended solids (TSS). Different studies have reported high values of BOD, COD and even the presence of Cr in effluents [ 13 , 36 , 39 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. Other compounds have been reported in these wastewaters, finding results of acidic pH between 3.4 ± 0.0351 and 5.96 ± 0.0351 [ 56 , 57 , 58 ] and basic pH between 8.0 ± 0.4 and 11.64 ± 0.53 [ 37 , 41 , 46 , 51 , 52 , 54 , 55 , 59 , 60 , 61 ]; in relation to TDS, typical values can have concentrations ranging from 2355 ± 85 mg*L −1 to 10,000 ± 800 mg*L −1 [ 9 , 37 , 39 , 42 , 61 , 62 ]; high concentrations have been recorded that can be between 10,560 ± 78 mg*L −1 and 72,400 ± 0.10 mg*L −1 [ 35 , 40 , 53 , 54 , 55 , 63 ]; as for BOD, the average values can be in low ranges from 160 ± 15.8 mg*L −1 to 1250 ± 38 mg*L −1 [ 37 , 39 ,…”

Σύνθεση Και Χαρακτηρισμός Νέων Προ-Πολυμερισμένων Ανόργανων Κροκιδωτικών Υλικών Και Εφαρμογή Τους Στην Επεξεργασία Νερού Και Αποβλήτων

“…13 κατά την ανάλυση με XRD είναι η εμφάνιση σχετικά έντονων κορυφών σε μικρές γωνίες (5-35 ο 2θ), ενώ ο χημικός τύπος με τον οποίο ταυτοποιήθηκε ήταν ο εξής…”

“…[10][11][12][13][14][15] , τόσο για την απομάκρυνση της θολότητας, όσο και της απορρόφησης στα UV 254nm , με δόση του κροκιδωτικού 2 mg Al/L. Στη συνέχεια, μελετήθηκε η αποτελεσματικότητα των κροκιδωτικών υλικών με την προσθήκη πολυηλεκτρολύτη (ΑPE) ως πρόσθετο στη δομή του κροκιδωτικού, εναλλακτικά της προσθήκης του πολυπυριτικού οξέος (pSi).…”

“…Al13 Cl 15 (OH)24 .37.5H 2 O. Η ταυτοποίησή του έγινε έπειτα από πολλές δοκιμές, καθώς όπως αποδείχτηκε τελικώς, η ευαισθησία της ανίχνευσής του με την τεχνική XRD επηρεάζεται σημαντικά από την παρουσία του σχηματιζόμενου NaCl.Αξιολογώντας τις εν λόγω τιμές προκύπτει ότι το PSiFAC 1.5-10-15 , το βέλτιστο υλικό για την επεξεργασία επιρυπασμένου νερού και δειγμάτων αποβλήτων, είναι το κροκιδώτικο με βάση το αργίλιο, που έχει το μεγαλύτερο αρχικά θετικό ζ-δυναμικό (+50.5 mV) και παρουσιάζει IEP σε τιμή pH 9,10. Το αρχικό μέγεθος σωματιδίων είναι 188,9 nm, τοποθετώντας το στην κατηγορία…”