Search

This paper reviews currently available methods for hydrolysis activity monitoring of the most commonly encountered enzyme categories in biological wastewater treatment. While highlighting the relevant methods for protein, lipid, carbohydrate, organic phosphate, and ester hydrolysis, the discussion of their pros and cons is predominantly aimed at revealing the relevance of the to-be-hydrolyzed substrates that are used in the methods. These "substrates" should mimic the proteins, lipids, or other polymers that are present in the wastewater and are in the reviewed methods (i) real substrates (i.e., naturally present in the wastewater), (ii) chromogenic substrates, or (iii) fluorogenic substrates. We conclude that exploiting relevant substrates such as casein or starch, containing fluorophores, has the highest potential for meaningful high throughput hydrolysis quantification and that lipase activity monitoring is still cumbersome. Monitoring the hydrolysis activity in biological wastewater treatment systems is an underdeveloped area. With this review, which aims at providing a condensed and practice-oriented overview, we hope to facilitate the start or continuation of such monitoring. This monitoring will only grow in importance, given the transition from wastewater treatment plants towards water resource recovery facilities. Key points: • Colorimetric-based methods are vulnerable to sludge matrix interference. • Bonds in p-nitrophenol-based methods are not representative for the targeted substrates. • Direct methods with relevant/real substrates are preferred. • Fluorophore-containing (real) substrates enable high throughput screening. [ABSTRACT FROM AUTHOR]

Proteins, an important fraction of the organic matter in wastewater, typically enter a treatment facility as high molecular weight components. These components are degraded by extracellular protein hydrolytic enzymes, denoted as proteases. Adequate protein hydrolysis monitoring is crucial, since protein hydrolysis is often a rate-limiting step in wastewater treatment. However, current monitoring tools lack a high sample throughput and reliable quantification. Here, we present an improved assay for high-throughput protein hydrolysis rate measurements in wastewater treatment applications. A BODIPY FL casein model substrate was implemented in a microplate format for continuous fluorescent quantification. Case studies on a conventional and a high-rate aerobic municipal wastewater treatment plant and a lab-scale, two-stage, anaerobic reactor provided proof-of-concept. The assay presented in this study can help to obtain monitoring-based process insights, which will in turn allow improving biological performance of wastewater treatment installations in the future. Key points: • Protein hydrolysis is a crucial step in biological wastewater treatment. • Quantification of the protein hydrolysis rate enables in-depth process knowledge. • BODIPY FL casein is a suitable model substrate for a protein hydrolysis assay. • High sample throughput was obtained with fluorescent hydrolysis quantification. [ABSTRACT FROM AUTHOR]

This study investigates the existing wastewater management situation in Ethiopia, with particular emphasis on university campus wastewater. The investigation was carried out by reviewing literature, reports, policy documents and field visits integrated with laboratory assessment. It was established that from the seven universities only two have functional wastewater treatment plants, but none of them meet effluent standards. Thesemainly centrally prescribed systemslack sustainability because of problems related to technology choice, affordability and technical skills. This paper proposes feasible rehabilitation strategies for the existing wastewater systems. A combination of policy instruments and integrated wastewater management strategies are proposed. Although based on specific data from Ethiopia, the findings and recommendations of this study also apply to other, similar, low-income countries where the population is booming but overall wastewater management planning is lagging behind. [ABSTRACT FROM PUBLISHER]

This article introduces a centrifugal compaction (spin tube) test to thoroughly evaluate polyelectrolyte conditioning on lab scale. In contrast to the well-known and widely applied existing tests (e.g., the beaker, the Jar settling, the free drainage, and the [sheared] capillary suction time test), the proposed spin tube test has a clear relation with the dewatering process taking place in a decanter centrifuge. First, based on the theory of centrifugal compaction, the solids stress of separate layers of sludge cake (obtained after spinning sludge in a lab centrifuge) is calculated. Next, the test was applied to assess in the lab the performance of three different polymers by evaluating the obtained sludge dryness. To verify and/or compare the results obtained with the spin tube tests, sheared capillary suction time tests were conducted and floc size distributions were analyzed. Finally, two of the three polymers evaluated in the lab were applied in the industrial sludge dewatering and drying system used at the wastewater treatment plant of Monsanto Antwerp in Belgium. Observed field performance was in perfect accordance with the spin tube tests. [ABSTRACT FROM AUTHOR]

Onsite individual wastewater treatment systems can provide a financially attractive alternative to a sewer connection in locations far from the existing sewer network. These systems are, however, relatively new, and practical experiences, especially long-term field studies, are lacking. Therefore, a thorough study of two compact biofilm-based, aerobic onsite systems, both of five population equivalents, was started in 2001. The assessment of the treatment performance of these systems, as well as the maintenance requirements and the characterisation of the feed are of great importance for the better understanding of the systems in order to optimise their design and performance. This paper presents an evaluation and discussion of the start-up and a starvation period of the two studied systems, followed by a characterisation of the incoming wastewater using activated sludge respirometry experiments in the context of the assessment and improvement of the denitrification process. Individual wastewater treatment systems are characterised by a rather long start-up period of 70--120 days. An important characteristic during the start-up is the nitrite peak, which indicates the initiation of the nitrification process. The respirometric experiments reveal that the failing denitrification is probably caused by an insufficient amount of readily biodegradable COD in the influent. [ABSTRACT FROM AUTHOR]

• Anaerobic co-metabolism is a promising strategy for removing OMPs with specific structural properties. • Transformation pathways of OMPs can be influenced by the microorganisms and enzymes involved in anaerobic digestion. • Elucidating the mechanisms underlying OMP biodegradation is crucial for enhanced elimination during wastewater treatment. The emerging presence of organic micropollutants (OMPs) in water bodies produced by human activities is a source of growing concern due to their environmental and health issues. Biodegradation is a widely employed treatment method for OMPs in wastewater owing to its high efficiency and low operational cost. Compared to aerobic degradation, anaerobic degradation has numerous advantages, including energy efficiency and superior performance for certain recalcitrant compounds. Nonetheless, the low influent concentrations of OMPs in wastewater treatment plants (WWTPs) and their toxicity make it difficult to support the growth of microorganisms. Therefore, co-metabolism is a promising mechanism for OMP biodegradation in which co-substrates are added as carbon and energy sources and stimulate increased metabolic activity. Functional microorganisms and enzymes exhibit significant variations at each stage of anaerobic digestion affecting the environment for the degradation of OMPs with different structural properties, as these factors substantially influence OMPs' biodegradability and transformation pathways. However, there is a paucity of literature reviews that explicate the correlations between OMPs' chemical structure and specific metabolic conditions. This study provides a comprehensive review of the co-metabolic processes which are favored by each stage of anaerobic digestion and attempts to link various functional groups to their favorable degradation pathways. Furthermore, potential co-metabolic processes and strategies that can enhance co-digestion are also identified, providing directions for future research. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Biological wastewater treatment generates huge amounts of waste sludge which need to be dewatered and eventually dried to minimize transportation and incineration costs. A characteristic feature of sludge in this context is that it turns into a sticky substance during its drying process inducing fouling problems in the drying installation. At the wastewater treatment plant of Monsanto in Antwerp, Belgium, one enclosed centrifuge-dryer system is used to dry the sludge. In the past, this installation had to be shut down regularly due to dryer fouling problems. To avoid these operational problems, a binary logistic regression analysis is presented in this research based on a 5-year database, resulting in an empirical model for the evaluation of the dryer fouling risk as a function of the sludge feed characteristics. The model inputs are the sludge volume index (SVI) and the dosing of clay additive and tertiary (flotation) sludge, the latter containing polyaluminumchloride (PACl), to the sludge feed of this particular system. By exploiting the knowledge captured by this model, the derived control strategy is based on the value of the SVI. Whenever the SVI is high the original high clay dosing to the feed needs to be maintained. At moderate SVI values, implying an intrinsically better sludge dewaterability, the strategy dictates a reduction in the clay dosing to the sludge feed to have a reduced sludge solids dryness after dewatering, thereby avoiding that the sludge exhibits its most sticky phase when passing the most fouling sensitive part of the dryer. When the SVI is lower than 50mL/g the control strategy states that conditioning of the sludge with PACl is required to mask the stickiness instead of postponing it, avoiding that the stickiness of the sludge already hampers the dewatering stage of the process. [Copyright &y& Elsevier]

Polyvinylidene difluoride (PVDF) based membranes have been used extensively for wastewater treatment due to their chemical and mechanical stability. However, membrane fouling remains a critical factor limiting the widespread use of membrane processes. To mitigate membrane fouling, patterned PVDF membranes were prepared via spray-modified non-solvent induced phase separation (s-NIPS) which resulted in membranes with large pattern heights of 750 ± 100 μm. Patterned membrane modules were then subjected to magnetically induced membrane vibration (MMV) applied perpendicular to the direction of the pattern to reduce the foulant deposition and delay the irreversible fouling in a submerged membrane bioreactor (MBR). Mere patterning resulted in a 70–300% decrease in membrane fouling rate and a doubled critical flux as compared to the flat counterpart. The introduction of membrane vibration further improved the membrane anti-fouling potential by prevention of foulant deposition through improved hydrodynamic conditions near the membrane surface and efficient removal of foulant deposition. Introducing an axial vibration of 5 Hz frequency dropped the fouling rate by an additional 40–60% and the critical flux for irreversible fouling was almost tripled from 15 L m−2 h−1 for the flat, non-vibrating membrane to 40 L m−2 h−1 for the s-NIPS patterned, vibrating membrane. A computational fluid dynamics (CFD) simulation with mesh motion at the patterned membrane interface confirmed the formation of vortices due to vibration, which are convected away from the membrane surface. The CFD results provided a sound basis for understanding the effect of membrane topography combined with vibration. These results suggest reduced fouling without the need for intense air scouring or frequent cleaning which can result in energy- and cost-effective filtration during MBR operation. [Display omitted] • Synergistics effects of membrane patterning and vibration for waste water treatment. • Moving mesh CFD performed at pattern, vibrating interface reveals anti-fouling mechanism. • Increased critical fluxes and lower total fouling rates due to efficient hydrodynamics. [ABSTRACT FROM AUTHOR]