Solar water pasteurizer: Productivity and treatment efficiency in microbial decontamination

Highlights

The treatment showed absence of total coliforms and E. coli, MPN <1.1 P. aeruginosa and 98.7% reduction for heterotrophic.

The heat recovery has great importance since it increased productivity by 110%.

The solar radiation cutting level for the pasteurizer is at about 6.6 MJ/m2 day.

The solar pasteurizer (2 m2 collector) produce 80 L/day, with 85 °C treatment temperature for 15 s.

The system guarantees total segregation between the contaminated water and the water in treatment.

Abstract

The ingestion of contaminated water is a major cause of disease and death in developing countries. The decontamination of water can be achieved by different methods of treatment. However, solar pasteurization shows promise for inactivating microorganisms at different temperatures. In this work, a solar pasteurization system operating by automated batches has been both designed and tested. A flat solar collector with 2 m2 of aperture, a heat exchanger, two solenoid valves, two thermoresistances and an electronic control were used to perform water treatment in different preprogrammed “set points”: 3600 s at 55 °C; 2700 s at 60 °C; 1800 s at 65 °C; 900 s at 75 °C and 15 s at 85 °C. The system showed advantages over other existing pasteurizers in literature when it comes to the possibility of performing treatment in several temperatures, the complete segregation between water masses and the ability of controlling water residence time in the solar collector. The use of heat exchanger has great importance since it implies increased productivity of about 110% and significant reduction of solar radiation cutting level at about 6.6 MJ/m2 day. The experimental data also showed that it was possible to achieve productivity of 80 L of treated water in a day of clear sky. Furthermore, the pasteurizer remained stable for elimination efficiency of the tested microorganisms, considering the 85 °C treatment temperature for 15 s. Bacteriological analysis after treatment showed absence of total coliforms and Escherichia coli, MPN <1.1 Pseudomonas aeruginosa and 98.7% average reduction of heterotrophic bacteria at different levels of water sample contamination.

Keywords

  • Solar pasteurization;
  • Safe water;
  • Microbiological decontamination;
  • Thermal inactivation;
  • Pathogens

Abbreviations

  • ANVISA, Brazilian National Agency of Sanitary Surveillance;
  • BGBLB, Brilliant Green Bile Lactose Broth;
  • CFU, Colony-forming units;
  • CREST, Centre for Research on Evaluation, Science and Technology;
  • E. coli, Escherichia coli;
  • EC, broth for E. coli;
  • EMB, Eosine Methylene Blue;
  • Hcoll, Accumulated solar irradiation in a day;
  • Hcut, Critical irradiation;
  • Icoll, Instantaneous irradiance;
  • ICU, Intensive Care Unit;
  • MPV, Maximum Permitted Value;
  • MPN, Most probable number;
  • NTU, Nephelometric turbidity unit;
  • PCA, Plate Count Agar;
  • PROCEL, National Program for Electrical Energy Conservation;
  • PTC, Parabolic trough concentrator;
  • PA, Presence and Absence of microorganisms test;
  • P. aeruginosa, Pseudomonas aeruginosa;
  • SODIS, Solar disinfection;
  • UV, Ultraviolet;
  • UFPE, Federal University of Pernambuco

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