Reclaimed Water

Abstract Wastewater treatment plants (WWTPs) are scrutinized by Environmental Authorities particularly regarding the compliance to discharge limit values fixed by national and local regulations. An integrated approach is necessary to achieve the objectives established with Directive 2000/60/EC (WFD) considering the ecological status of the receiving water body and the quality of the discharge. Specifically, documentary, technical, management and analytical controls should be developed. Moreover, integrative information on the behaviour of the activated sludge in the aeration tank can be useful for plant managers as well as for the regulating Authorities. The study presents the experience concerning WWTP regulation considering the analytic assessment of the discharge as well the monitoring of the Sludge Biotic Index (SBI) for activated sludge. Data from monitoring during the period 2008–14 on SBI values and chemical and microbiological data on the discharges of a sample of 35 WWTPs in the province of Venice (north-east Italy, Veneto region) are presented and discussed. Together with chemical and microbiological analysis, the SBI appears to be a highly useful index for the integrative assessment of plant functionality, in particular when monitoring and identifying critical situations that can determine the exceedance of discharge limit values. The SBI method, in an integrated control approach, can be used for small and medium sized WWTPs that only treat domestic wastewaters. In a case by case assessment this may even substitute part of the analytical monitoring carried out in the WWTPs' control process.

Over the last few decades adsorption has gained paramount importance in industry and environmental protection. Adsorption processes are widely applied for separation and purification because of the high reliability, energy efficiency, design flexibility, technological maturity and the ability to regenerate the exhausted adsorbent. One method of important extending the adsorption treatment processes is biofiltration. The biological filter relies on the activities of the community of micro-organisms that become attached onto the filter media. Microbes oxidize organic matters in water to produce energy and therefore available nutrients sources in feed water are essential for their development. Biofiltration can effectively remove organic matter that is not able to be removed from water and biologically treated sewage effluent in conventional sewage treatment. The microbial attachment process, the factors that influence biological filtration, the kinetics of microbial growth and details of the microbial community in the biofilter are discussed in detail. There are several types of biofilters including submerged filters, trickling filter, bed filter, fluidised bed. The different biofilters are described and a comparison between them is provided. The application of biofilters for treating various types of wastewater effluent is detailed.

Hybrid processes combining activated carbon and nanofiltration have been studied to identify the optimum solution for advanced wastewater treatment in high quality water reclamation and reuse. With a focus on the removal of bulk and trace organic compounds the investigation identified three promising process combinations, namely powdered activated carbon followed by nanofiltration (PAC/NF), granular activated carbon followed by nanofiltration (GAC/NF) and nanofiltration followed by granular activated carbon (NF/GAC). The removal potential was examined in lab and pilot scale for a range of refractory pharmaceuticals and industrial chemicals typically detected in effluent in trace concentrations ranging from ng/L to μg/L. Fluorescence excitation emission spectroscopy was employed for the investigation of the fate of effluent organic matter. The optimum strategies for operation of the hybrid processes were determined in pilot scale. The experiments were conducted at the Wastewater Treatment Plant Aachen Soers providing an effluent of high quality with low dissolved organic carbon (DOC) concentrations of about 5 mg/L.