Polyamid halı terbiyesi atıksularının karakterizasyonu ve biyolojik arıtılabilirliği

Abstract

Textile industry uses natural and artificial fibres and produces fabric and other textile products which contain also carpet material. So far, the majority of studies on industrial wastewaters has been conducted on plant effluents and mostly reflects an end of pipe approach. The results in the literature mainly report to what extent wastewaters are biodegradable but contain little or no information on the nature of biologically resistant compounds or COD fractions. Industrial wastewaters include a waste array of chemicals used in different steps of the manufacturing process. The impact of these chemical can best be envisaged in different wastewater streams are evaluated in terms of their individual biodegradation characteristics. Respirometric methods and the use of oxygen uptake rate in aerobic systems as a major model parameter has been a major asset in the identification of COD fractions with different biodegradation rates and in model evaluation and calibration of experimental data. These methods are especially useful in cases individual specific pollutants are hard to identify. This paper evaluates biological treatability of wastewaters generated from polyamid based carpet processing and manufacturing. It involves detailed characterization, kinetic description and respirometric modelling of different wastewater streams and the composite effluent. The average COD of the wastewater is measured as 1675 mg/l, varying in the range of 1450-1900 mg/l. Light color dying wastewaters are utilized for biological treatability due to a higher dye content associated with this process. COD fractionation indicates a 80-90 % soluble COD fraction, almost totally slowly biodegradable with a very small readily biodegradable portion. A dual hydrolysis mechanism best describes the biodegradation of the slowly soluble fraction, based on respirometric evaluations. Experimental results have been tested by a multi-component mathematical model using the endogenous decay approach and hydrolysis constants corresponding to the slowly biodegradable COD fractions have been evaluated using curve fitting. The very low rate coefficients characterizing the hydrolysis of the large part of the soluble COD bring interesting difficulties in the design of biological treatment systems. Design applications for continuous-flow activated sludge systems identify an unusually long hydraulic retention time of 3 days at a sludge age of 10 days. Respirometric analysis of the main wastewater streams provided in dept information on the biodegradation characteristics, which could be translated into the composite plant effluent and confirmed by appropriate COD mass balance. The evaluation showed that acrylic and polyamid carpet finishing wastewater was quite different from domestic sew¬age and other textile effluents in terms of COD fractionation and biodegradation. It could be characterized by dual hydrolysis of soluble and particulate COD components occurring at much slower rates compared to other wastewaters. The hydrolysis rate of the particulate COD was almost comparable to endogenous decay. Furthermore, in biological treat-ability studies, respirometry based modeling showed that the acclimated biomass exhibited similar biological response to individual wastewaters originated from each process step compared to composite sample characterizing the overall process scheme of acrylic and polyamid carpet production. On the other hand, simulation results on performance prediction and overall treatability indicate that slow hydrolysis of the major fraction of soluble COD, although rate limiting, does not pose a significant problem for effluent quality.

Özet

Polyamid esaslı halı işlem ve üretiminden oluşan atıksuların biyolojik arıtılabilirliğini değerlendiren bu çalışma, farklı atıksu akımları ve kompozit çıkış suyunun detaylı karakterizasyonu, kinetik tanımlaması ve respirometrik modellemesini içermektedir. Günümüze kadar yapılan endüstriyel atık sudaki çalışmaların çoğunluğu tesis dışına akan maddeleri ve genellikle de boru sonu yaklaşımını üzerinedir.Atıksuyun ortalama KOİ'si 1675 mg/l olup 1450-1900 mgKOİ/l aralığında değişmekte olup biyolojik arıtılabilirlik çalışmalarında açık renk boyama atıksuları kullanılmıştır. Organik maddenin %80-90 'ı çözünmüş olmasına karşın çok az bir kısmı biyolojik olarak kolay ayrışabilen ve hemen hemen tamamı yavaş ayrışabilir formdadır. Deney sonuçlarının değerlendirilmesinde respirometrik yöntem ve"aerobik sistemdeki oksijen tüketim miktarı başlıca model parametresi olarak kullanılmıştır. Respirometrik değerlendirmeler çerçevesinde yavaş ayrışan fraksiyon en iyi şekilde ikili hidroliz mekanizması ile tanımlanmaktadır. Sürekli ve tam karışımlı aktif çamur sistemleri için dizayn uygulamaları, 10 günlük çamur yaşında pek yaygın olmayan 3 günlük uzun bir hidrolik bekletme süresini tanımlamaktadır.