Biochar from recovered cellulose as new admixture in constructed wetlands for micropollutant removal: A circular approach

This study aimed to evaluate the suitability of biochar produced by pyrolysis from recovered wastewater cellulose and activated biologically as an admixture in Constructed Wetlands (CWs) when applied as a post-treatment step to remove micropollutants (MPs) from municipal wastewater effluent. Two planted vertical flow mesocosm CWs with cellulose-based admixtures of different origins (plant residue and recovered toilet paper) were fed with a municipal wastewater effluent representative for rural catchments. The results showed an average MPs elimination of 89.1 % for the activated biochar produced from recovered cellulose when 15 relevant compounds are considered and a reduction of the risk from compounds cocktail below the maximum acceptable level having diclofenac, carbamazepine, PFOS, ciprofloxacin and clarithromycin as main risk drivers (Risk Quotient > 1). The implementation of a circular approach to reduce MPs was finally conducted for the Blies catchment (Saarland region in Germany) characterized by low population density and small, sensitive water bodies. This approach demonstrates the feasibility of combining cellulose recovery with a fine sieve in large wastewater treatment plants (WWTPs) and providing biochar produced from recovered cellulose as an admixture to small WWTP where CW is an affordable solution for MP mitigation.

Effect of sewage sampling frequency on determination of design parameters for municipal wastewater treatment plants

The uncertainty associated with the determination of load parameters, which is a key step in the design of wastewater treatment plants (WWTPs), was investigated on the basis of data sets from 58 WWTPs. A further analysed aspect was the organic load variations associated with variable sewage temperatures. Data from 26 WWTPs with a high inflow sampling frequency was used to simulate scenarios to investigate the effect of lower sampling frequencies through a Monte Carlo approach. The calculation of 85-percentile values for chemical oxygen demand (COD) loadings based on only 26 samples per year is associated with a variability of up to ±18%. Approximately 90 samples per year will be necessary to reduce this uncertainty for estimation of COD loadings below 10%. Hence, a low sampling frequency can potentially lead to under- or overestimation of design parameters. Through an analogous approach, it was possible to identify uncertainties of ±11% in COD loading when weekly average data was used with four samples per week. Finally, a tendency to lower COD input loads with increasing temperatures was identified, with a reduction of about 1% of the average loading per degree Celsius.

A new approach to improve sludge dewatering using a semi-continuous hydraulic press system

In future, it will be necessary to incinerate an increasing proportion of the sludge produced by public wastewater treatment. In this context, equipment for more effective dewatering of sewage sludge is required. A hydraulic press system (Bucher HP) which has been used to date in the food industry could represent an alternative to the sludge dewatering systems currently used. The basic suitability of this press system was demonstrated in comprehensive industrial-scale trials at the Glarnerland STP (Switzerland). Dry solids contents of up to 43% were measured in the pressed sludge. Currently, the optimization of individual process parameters is being investigated in a pilot plant at the Schwelm STP operated by Wupperverband (Germany).

Lamella separators in the upgrading of a large urban sewage treatment plant

Wupperverband is using lamella separators for the upgrading of its Kohlfurth sewage treatment plant that is currently in progress. The lamellae positioned at the outlet of the biological treatment stage already remove part of the biomass in the activation basin and prevent it from reaching the final clarification stage. This preliminary separation system reduces solids concentration in the biological treatment system without negative impact on final clarification and therefore also lowers the basin capacity needed, with positive effects on costs. This article gives an overview of the separation performance achieved.

Measures and costs of integrated river basin management--the Wupper example

The implementation of the European Water Framework Directive entails additional costs in the areas of management, monitoring and water quality. As a first estimate, an attempt is made to assess the effects of implementation on the development of costs in a sub-basin, taking the Wupperverband as an example. The work and measures required are presented and the costs are assessed. On this basis, a cost estimate for the maximum time required for the implementation of the WFD is made. This takes into account all the relevant tasks in the area of the association with respect to rivers.

Model structure identification for wastewater treatment simulation based on computational fluid dynamics

The objective of this presented project is to use the results of an CFD simulation to automatically, systematically and reliably generate an appropriate model structure for simulation of the biological processes using CSTR activated sludge compartments. Models and dynamic simulation have become important tools for research but also increasingly for the design and optimisation of wastewater treatment plants. Besides the biological models several cases are reported about the application of computational fluid dynamics ICFD) to wastewater treatment plants. One aim of the presented method to derive model structures from CFD results is to exclude the influence of empirical structure selection to the result of dynamic simulations studies of WWTPs. The second application of the approach developed is the analysis of badly performing treatment plants where the suspicion arises that bad flow behaviour such as short cut flows is part of the problem. The method suggested requires as the first step the calculation of fluid dynamics of the biological treatment step at different loading situations by use of 3-dimensional CFD simulation. The result of this information is used to generate a suitable model structure for conventional dynamic simulation of the treatment plant by use of a number of CSTR modules with a pattern of exchange flows between the tanks automatically. The method is explained in detail and the application to the WWTP Wuppertal Buchenhofen is presented.

Provision of data for on-line simulation

A crucial factor for the quality and results of the on-line simulation of a municipal sewage treatment system is the provision of the requisite data in adequate quality and density. Since the measured data cannot be incorporated in a simulation model without prior processing, it should be prepared in such a way that it can be converted to the model-related input quantities. If individual input measuring signals fail, substitute value concepts must be developed which are based on the remaining information. With this it is possible to ensure the continuous provision of data. Various approaches are possible in seeking a solution to this problem. At the Wupperverband a detailed programme of investigation on the subject area of the processing of inflow data is being implemented as a component of future on-line simulation at Wuppertal-Buchenhofen STP.