Search

Digital textile printing (DTP) is a game-changer technology that is rapidly expanding worldwide. On the other hand, process wastewater is rich in ammoniacal and organic nitrogen, resulting in relevant issues for discharge into sewer system and treatment in centralized plants. The present research is focused on the assessment of the partial nitritation/anammox process in a single-stage granular sequencing batch reactor for on-site decentralized treatment. The technical feasibility of the process was assessed by treating wastewater from five DTP industries in a laboratory-scale reactor, in one case investigating long-term process stabilization. While experimental results indicated nitrogen removal efficiencies up to about 70%, complying with regulations on discharge in sewer system, these data were used as input for process modelling, whose successful parameter calibration was carried out. The model was applied to the simulation of two scenarios: (i) the current situation of a DTP company, in which wastewater is discharged into the sewer system and treated in a centralized plant, (ii) the modified situation in which on-site decentralized treatment for DTP wastewater is implemented. The second scenario resulted in significant improvements, including reduced energy consumption (− 15%), reduced greenhouse gases emission, elimination of external carbon source for completing denitrification at centralized WWTP and reduced sludge production (− 25%). Electronic supplementary material The online version of this article (10.1007/s11356-020-11231-y) contains supplementary material, which is available to authorized users.

Digital textile printing is a rapidly spreading technology in the textile finishing industry due to the great advantages in making printing much more flexible. On the other hand, wastewater originating from rinsing baths are rich in nitrogen (up to 600 mg/L of ammonium nitrogen) due to the massive use of urea in conditioning the textile before printing. Such high concentration prevents the direct discharge into water bodies or even in public sewers and specific dedicated on-site pre-treatment is necessary. PN/anammox processes can offer an economically feasible alternative to conventional nitrogen removal processes, as these require a COD/N ratio of at least 8. The first results of the EU-LIFE DeNTreat project, consisting in the start-up of PN/anammox lab and pilot scale reactors are promising in spite of the variability of the characteristics of the wastewater originating from rinsing digitally printed textiles.

Textile effluents are characterised by high content of recalcitrant compounds and are often discharged (together with municipal wastewater to increase their treatability) into centralized wastewater treatment plants with a complex treatment scheme. This paper reports the results achieved adopting a granular sludge system (sequencing batch biofilter granular reactor - SBBGR) to treat mixed municipal-textile wastewater. Thanks to high average removals in SBBGR (82.1% chemical oxygen demand, 94.7% total suspended solids, 87.5% total Kjeldahl nitrogen, 77.1% surfactants), the Italian limits for discharge into a water receiver can be complied with the biological stage alone. The comparison with the performance of the centralized plant treating the same wastewater has showed that SBBGR system is able to produce an effluent of comparable quality with a simpler treatment scheme, a much lower hydraulic residence time (11h against 30h) and a lower sludge production. © 2014 Elsevier Ltd.

The textile industry releases highly polluted and complex wastewaters, which are difficult to treat and require numerous treatment steps. Innovative technologies for on-site treatment at each factory would permit cost reduction. For this reason, we ran a laboratory-scale study to assess the suitability of a sequencing batch biofilter granular reactor (SBBGR) for textile wastewater treatment, testing four different types of wastewater. Results demonstrate that wastewater characteristics greatly affect the reactor efficiency. Hence, a pre-study is advisable to define the best operational conditions and the maximum treatment capability for the wastewater under analysis. Nevertheless, SBBGR is a valuable biological treatment, effective in the reduction of pollutant load with stable performances despite the variability in wastewater composition. Tests with ozone integration have demonstrated that it is possible to dose small quantities of ozone to obtain an effluent suitable for direct discharge. However, a dynamic ozone dosage should be used to optimize the process as the correct ozone dose strongly depends on the wastewater composition.

Textile wastewater is difficult to treat as it usually contains considerable amounts of different pollutants, which are often recalcitrant, toxic and inhibitory. Therefore, complex treatment schemes based on the sequence of various steps are usually required for an effective treatment. This explains why textile effluents are often treated in centralized plants and sometimes mixed with municipal wastewater. The adoption of new technologies for on-site treatment, instead, would be optimal, deeply reducing treatment costs. An innovative technology exhibiting several characteristics appropriate for the attainment of such a goal is sequencing batch biofilter granular reactor (SBBGR). To assess the suitability of this technology, two lab-scale reactors were operated, treating mixed municipal-textile wastewater and a pure textile effluent, respectively. Results have demonstrated that mixed wastewater can be successfully treated with very low hydraulic retention times (less than 10 hours). Furthermore, SBBGR shows to be an effective pre-treatment for textile wastewater for discharge into sewer systems. The economic evaluation of the process showed operative costs of 0.10 and 0.19 € per m(3) of mixed wastewater and textile wastewater, respectively.

This paper reports the results obtained using the sequencing batch biofilter granular reactor (SBBGR) for the treatment of the wastewater from a dyeing and finishing factory. The treatment of such a wastewater is challenging as it usually contains considerable amounts of different recalcitrant, toxic and inhibitory pollutants, which results in low biodegradability and in the need for numerous treatment steps. Different operational conditions were tested in order to assess SBBGR performance as a function of the applied organic and hydraulic load and to verify its suitability for on-site dyeing wastewater treatment at each factory. The reported measurements demonstrate how this innovative biological technology exhibits various promising features for this purpose, as good treatment efficiencies can be achieved even at high organic load values (2.4–2.6 kg COD m −3 d −1 ) and with hydraulic retention times lower than one day. Furthermore, the treatment is characterized by a sludge production as low as 0.1 kg of dry sludge per kg of COD removed. Therefore, SBBGR has proved to be an effective pre-treatment for dyeing textile wastewater before discharge into municipal sewer system, as it produces a suitable effluent using just only one biological step with high hydraulic and organic loadings and low sludge production.

Textile effluents are among the most difficult industrial wastewaters to treat because of their compositional variability and of the presence of numerous different chemicals intentionally designed to resist degradation. Though biological technologies offer a cheaper and more environmental friendly alternative for the treatment of textile effluents, an additional step to remove recalcitrant compounds is still needed. Integrated biological and chemical treatment is a rather new approach that allows improving treatment performance and stability without increasing too much treatment costs. Ozone integration in a sequencing batch biofilter granular reactor was tested at laboratory scale for treating a printing wastewater characterized by high concentrations of surfactants and nitrogen. The process was optimized in terms of applied organic load and ozone dose. The results have shown that the process assures the possibility to comply with the limits for direct discharge for all investigated parameters by operating at an organic load value lower than 1.5 kgCOD/m3 d and with an ozone dose of 135 mg/l. A synergetic biological and chemical oxidation activity was observed with a ratio between ozone dose and COD removed lower than 0.75. Finally, the process was characterized by a sludge production as low as 0.17 kgTSS/kgCODremoved due to the high biomass concentration in the biological system used.

The paper presents the results obtained at laboratory, pilot and demonstrative scale with granular activated carbon adsorption as a mean to obtain effluent suitable as water supply for textile finishing industries, that require very stringent limits in terms of COD and colour removal. Laboratory scale tests evidenced that the specific carbon adsorption capacity, both for COD and colour, is highest for a sand-filtered + clariflocculated effluent and lowest for the sand-filtered + ozonated secondary effluent. Pilot and demonstrative scale tests were performed on three filters (0.3, 0.3 and 20 m3 of GAC each) fed with the full scale ozonated secondary effluent.

An intrinsic characteristic of the Italian industrial production system is the presence of several industrial districts with a prevalent manufacturing typology, in which several small and medium enterprises dealing with the same or similar products are concentrated in a small territory. An important textile district is localized in Como area, north of Italy. In many cases, industrial districts are served by large treatment plants that receive the majority of the pollution loading from several small and medium enterprises that do not have internal treatment facilities. The treatment fee is determined by regional regulations; commonly, the single wastewater stream connected to the sewer is billed by the sewer manager to the source industry on the basis of the flow rate and of a complex formula that takes into account a series of parameters. This method is unable to properly evaluate the relationship between treatment fee and actual treatment costs, since conventional physical-chemical and biochemical parameters are not necessarily linked to wastewater treatability. New advanced respirometric methodologies could be used as wastewater characterization techniques, since they are particularly suited to represent the effect of a given wastewater on the final wastewater treatment plant. Hence, they could be better correlated to treatment costs. The instrument developed is composed of two parallel moving bed continuous flow completely mixed reactors of the working volume of about 5 l each, equipped with oxygen sensors connected to a computer that acts as a controller and as a data acquisition and processing unit. Some examples of experimental results obtained with synthetic waste and with real sewage are presented.

A program in BASIC is described which allows accurate quantification of some numerical parameters that can be objectively correlated to biological indexes in sigmoid biological events. Attention was focused on the polymerization process of actin (a muscle protein with a mol. wt of 42,000 daltons) studied as the variation in the OD360 index with time. The experimental points, if plotted, can be well approximated by a rational function of the type delta OD360 = f(t), which passes through the origin and can be represented graphically by a sigmoid curve. The program was very helpful in comparing the experimental curves and in analysing significant parameters, such as maximum velocity and asymptote, that characterize these curves and whose interpretation would otherwise be purely subjective.