Ricardo de Lima Isaac

Urban water reuse: microbial pathogens control by direct filtration and ultraviolet disinfection

Physicochemical treatment efficiency for unrestricted urban water reuse was evaluated at a conventional activated-sludge wastewater treatment plant (WWTP). Pilot plant set-up consisted of an alum coagulation step, granular media upflow flocculation and direct downflow dual-media filtration followed by ultraviolet disinfection (dose of 95 mJ cm⁻²). Optimum aluminum sulfate dosage of 10 mg L⁻¹ and coagulation pH 7.0 were preset based on bench scale tests. Under WWTP stable operation, water quality met United States Environmental Protection Agency (USEPA) suggested guidelines for unrestricted urban reuse regarding turbidity (mean value 1.3 NTU) and suspended solids (mean value 2.1 mg L⁻¹). When WWTP overall plant performance dropped from 90 to 80% (although BOD value stayed below 6 mg O₂ L⁻¹, suggesting unrestricted reuse), solids breakthrough in filtrate was observed. Microorganism removal rates were: total coliforms 60.0%, Escherichia coli 63.0%, Giardia spp. 81.0%, and helminth eggs 62.5%; thus organisms still remained in filtrate. Ultraviolet (UV) disinfection efficiency was 4.1- and 3.8-log for total coliforms and E. coli, respectively. Considering low UV efficiency obtained for helminths and the survival of protozoa and helminths in the environment, effluent quality presents risk to public health if destined for unrestricted urban reuse.

Cyanobacterial community and microcystin production in a recreational reservoir with constant Microcystis blooms

Cyanobacterial blooms are increasing worldwide favored by eutrophic conditions of aquatic ecosystems associated with climatic perturbations. Generally, inland lentic systems are more susceptible to the development of harmful blooms. In the Salto Grande Reservoir (Brazil), Microcystis is the most common bloom-forming genus along with a wide range of co-occurring and less-known cyanobacteria taxa. The cyanobacterial community and microcystin production were studied in Salto Grande Reservoir applying biological, toxicological, and molecular approaches. Thirteen cyanobacterial strains belonging to eight genera were isolated and taxonomically investigated based on morphological traits and phylogenetic analyses of their 16S rRNA gene sequence. The morphotypes identified were, in general, in agreement with their phylogeny. The presence of non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) was investigated using PCR gene amplification, which were detected in 76.9 and 84.4% of the strains, respectively. Positive enzyme-linked immunosorbent assays (ELISA) reactions for microcystins were obtained only from the strain Leptolyngbya sp. CENA129. ELISA and high-performance liquid chromatography (HPLC) analyses of the environmental water samples showed the highest microcystin concentration during the dry and rainy seasons, respectively. This study highlights that microcystin production must be suspected in benthic forms as well as in genera that are morphologically similar but belonging to other evolutionary lineages.

WTP and WWTP sludge management: a case study in the metropolitan area of Campinas, southeastern Brazil

Disposal of sludges generated at water treatment plants (WTPs) and wastewater treatment plants (WWTPs) located in highly urbanized regions challenges water industry. Legal restrictions based on public health and sustainability push managers forward in order to find beneficial use markets rather than deficit and high-cost landfilling. A GIS-based linear optimization method for sludge management was firstly proposed. The metropolitan area of Campinas belongs to the watershed of the rivers Piracicaba, Capivari, and Jundiaí (PCJ), which comprises 76 municipalities, representing over 5 million urban consumers, supplied by 100 WTPs and 116 WWTPs. An assessment of soils feasibility for WWTP sludge reception was carried out. The beneficial uses assumed to be the best for WTP and WWTP sludges were, respectively, addition in the industrial process of ceramic bricks manufacture, and application on sugarcane crop areas for ethanol production. Three scenarios were set for sludges from WTPs and also for WWTPs. Those scenarios represented maximum, intermediate, and minimum reception capability for each reception location or area. Ceramic industries located within PCJ watershed showed to be capable of receptioning the total amount of WTP sludges, if a minimum 2% mass/mass replacement of raw materials (mainly clay) is provided. There are plenty of feasible areas for WWTP sludge application; thus, sludge agronomic quality and farmers’ acceptance constitute the only steps to climb. This paper brings an innovative tool regarding sludge management which may be useful to decision-makers, especially wherever several sources and reception areas are playing on game board. The proposed method can be applied at different locations and for other sludge uses.