Re-thinking sludge management within the Sustainable Development Goal 6.2.

Sustainable Development Goal 6.2 of the Agenda 2030 is addressed to achieve access to adequate and equitable sanitation and hygiene for all. Further, one of the major principles underlying the Lisbon Charter is that sustainable and safe management of wastewaters are fundamental to the health of communities and their sustainable socio-economic development. Within this framework, the management of sewage sludge in a sustainable manner is one of the critical issues facing modern society, due to the growing rise of its production, increasing difficulties in properly locating treatment and disposal works, and complying with more stringent environmental quality requirements, thus requiring a re-thinking of its management. This paper discusses major concepts and principles for re-thinking the sludge management in order to achieve the above-mentioned objectives.

Enhanced organic pollutant removal influenced by activated-ferric-sludge.

The primary goal of this study was to compare the pollutant removal efficiency of the reactivated activated-ferric-sludge (AFS) with that of the activated sludge (AS). Most tested organic pollutants were preferably removed by reactivated AFS. The optimal reactivated conditions for AFS were a reactivation time of 3 h, pH of 5-9, AFS dose of 5 g/L and dissolved oxygen of 2-6 mg/L. The results revealed a positive correlation between microbial activity and the removal efficiency of organic pollutants, with a higher microbial activity being associated with a better removal efficiency of organic pollutants. Additionally, variations in extracellular polymeric substances were found to be crucial to the microbial activity and adsorption capacity of reactivated AFS. After reactivation, reactivated AFS was superior to AS for the removal ofmost pollutants. Finally, the mechanism of AFS reactivation was investigated. Overall, the results of the present study demonstrate that reactivated AFS has the potential for widespread application in the removal of organic pollutants during the wastewater treatment process.

Characterization: a necessary tool in sludge management.

Sludge management is one of the critical issues facing modern society due to the fast increase in its production as a result of extended sewerage, new work installations and up-grading of existing facilities. In order to (i) properly perform the utilization and disposal operations, (ii) correctly fulfil the legal requirements and (iii) build stakeholder and public confidence, it will be necessary to establish defined outlet procedures/routes and guarantee a good sludge quality. Therefore, characterization to evaluate sludge chemical, biological and physical properties is a necessary tool in sludge management. However, characterization procedures often specify different methodologies, materials and accessories; so results obtained in different places may not be fully reliable. Also comparison of the results can be problematic because they have not been obtained under standardized conditions. Consequently, the development of standardized validated characterization methods and procedures becomes necessary too. Further, the development of standardized characterization methods and procedures should be supported by the preparation of 'guidelines' of good practice for the different options of sludge use and disposal in order to give guidance to producers/users on how to meet legislation requirements and perform sustainable operations. In this paper the main parameters for sludge characterization are discussed and developments in European standardization outlined.

The preparation of synthetic sludge for lab testing.

For carrying out sludge lab-scale tests, and interlaboratory trials for standards validation, the availability of samples with "certified and constant" characteristics is required. When "dried sludge" samples cannot be used, problems arise because (i) most fresh sludge characteristics change with storage time, also because some preservation practices are not applicable or their effects unknown, (ii) some fresh sludge characteristics are strongly affected by handling, and (iii) fresh sludge requires particular precautions and authorization for transportation. This means that using "fresh sludge" samples cannot guarantee reliability and reproducibility of results, so a valid alternative consists in testing "synthetic suspensions" samples to be on-site prepared. This should also give the possibility to compare results obtained in different places and times. Within this framework, Task Group 3 (TG3) of Working Group 1 (WG1) of Technical Committee 308 (TC308) of European Standardization Committee (CEN) undertook the preparation of a Technical Report dealing with the preparation of synthetic suspensions, both inorganic and organic, in repeatable conditions, able to describe the behaviour of a real sludge. This paper discusses a proposal for ingredients and modalities to prepare such synthetic suspensions that will be systematically tested in already planned lab experiments to define an optimal recipe.

European developments in standardisation of sludge physical parameters.

Characterisation is an important step in sludge management as it allows sludge properties to be evaluated and behaviour predicted. This is well recognised by the European Union (EU) countries which consider necessary the development of standardised sludge characterisation methods and procedures because objective and transparent regulations allow sludge management to be properly performed, legal requirements correctly fulfilled, and public confidence built. To this end, the European Committee for Standardization (CEN) established the Technical Committee 308 (TC308) whose scope is the production of Standards for sludge characterisation, and of Guides of good practice. In this field, physical properties are of great importance as they allow the prediction of sludge behaviour when handled and submitted to almost all treatment and utilisation/disposal operations. Activity of CEN/TC308 is developed in three Working Groups (WG) and several Task Groups (TG); in particular, TG3 of WG1 deals with physical parameters. In this paper developments regarding Standards for evaluation of capillary suction time, specific resistance to filtration, compressibility, settleability, thickenability, and calorific value, and Technical Reports dealing with a procedure for laboratory chemical conditioning and with sludge consistency (flowability/solidity) are briefly outlined. The results of relevant inter-laboratory tests for the validation of above standards are summarised.

Sludge production and management processes: case study in China.

In 2010, the sewage sludge production rate will be 178,500 t dried solids (ds) for Beijing and 294,000 t-ds for Shanghai, respectively. Beijing adopts a centralized system to stabilize 78% of her sludge in three rural Stabilization Centres. Aerated composting technique will be used. Shanghai on the contrary decentralizes the management plan to treat the sludge on site. Diverse treatment trains, such as aerobic/anaerobic digestion, drying, incineration, and composting will be applied. Production rate, treatment plan, and the associated costs, energy consumption, carbon dioxide emission, and risk assessment for heavy metals and pathogens on human health were evaluated in this report for sludges yielded in Beijing and Shanghai, China.

From sludge to resources through biosolids.

The paper gives an overview of the possibilities to achieve a more sustainable sludge management strategy by recovering and reusing valuable products as much as possible. Discussion separately deals with the recovery of products suitable for "material" uses and those for "energy" ones. Discussion on material recoveries includes organic matter, nutrients, carbon source, coagulant, bricks, pumice, slag, artificial lightweight aggregate (ALWA) and Portland cement. Regarding energy recovery, (i) conversion processes, including thermo-chemical conversion of dry sludge to oil, thermo-chemical liquefaction of wet sludge to oil and conversion/combustion processes, (ii) deep shaft wet air oxidation, and (iii) gasification processes, including starved air combustion, are outlined. Only general indications are given because the selection of an appropriate system for sludge management is strongly influenced by many other important factors, such as local economy and geography, climate, land use, regulatory constraints and public acceptance of the various practices. Also, the conventional and more traditional recycling options, like agricultural and other land uses, and incineration with energy recovery, are not dealt with because they are well known and extensively discussed elsewhere.

Sludge characterization: the rôle of physical consistency.

The physical consistency is an important parameter in sewage sludge characterization as it strongly affects almost all treatment, utilization and disposal operations. In addition, in many European Directives a reference to the physical consistency is reported as a characteristic to be evaluated for fulfilling the regulations' requirements. Further, in many analytical methods for sludge, different procedures are indicated depending on whether a sample is liquid or not, is solid or not. Three physical behaviours (liquid, paste-like and solid) can be observed with sludges, so the development of analytical procedures to define the boundary limit between liquid and paste-like behaviours (flowability) and that between solid and paste-like ones (solidity) is of growing interest. Several devices can be used for evaluating the flowability and solidity properties, but often they are costly and difficult to be operated in the field. Tests have been carried out to evaluate the possibility to adopt a simple extrusion procedure for flowability measurements, and a Vicat needle for solidity ones.

Sludge incineration tests on circulating fluidised bed furnace.

Results of sludge incineration tests on a demonstrative fluidised bed furnace are reported and discussed. They show that particulate, heavy metals and acidic compounds in the emissions can be easily controlled both when sludge is spiked with chlorinated hydrocarbons up to a chlorine concentration in the feed of 5%, and when the afterburner is switched off. As for organic micropollutants, polynuclear aromatic hydrocarbons (PAH) were much lower than the Italian limits of 10 microg/m3 (no limits are at present considered in the European Directives). Dioxins (PCDDs) and furans (PCDFs) in some tests exceeded the limit of 0.1 ng/m3 (TE) but the concentrations in the fly ashes were much lower, thus evidencing a possible presence of contaminants in gas phase. PAHs and PCDD/PCDFs were not depending on the afterburning operation, the presence of organic chlorine in the feed sludge and the copper addition to sewage sludge.

Evolution of sewage sludge regulations in Europe.

The shape of sewage sludge regulation in Europe is outlined as it undergoes a period of rapid evolution. The overall governing policy is embodied in European Directive ED91/156, the Waste Basis Directive, which sets general parameters for waste management. Descriptions are given of the terms of the more specific directives that apply to the major routes for sludge management: land application, composting incineration, and landfill.

Differences and similarities in the personality structure of 327 women with eating disorders.

The symptomatology of Eating Disorders (ED) varies considerably and it is of interest to determine whether one can attribute this to different personality structures and hence establish the most effective treatment. The present study investigates the psychopathological characteristics of clinical ED subjects divided by diagnostic subtypes, age at onset and duration of disorder on admission. Three hundred and twenty-seven women were administered the EAT 40 and MMPI. One-way ANOVA and Bonferroni post-hoc multiple comparisons were performed on subsamples: no significant differences emerged with regard to age at onset and duration of ED, whereas the diagnostic subtypes obtained significantly different MMPI validity scale scores. These results can be referred to a common core of ED represented by cognitive organization and personal meaning.