Biomedical subjects

C Maya

Publications and source records attributed to C Maya.

7 recordsLinked to original sources

PubMed2006

Particle size distribution to design and operate an APT process for agricultural wastewater reuse.

Total suspended solids is a parameter commonly used to operate and design coagulation-flocculation processes. Nevertheless, their application for an advanced primary treatment (a high performance but low dose demand coagulation processes coupled with a high rate sedimentator, sometimes called enhanced primary treatment) is not the best option to produce an effluent for agricultural irrigation. This paper compares the best operating conditions obtained using the TSS or the PSD (particle size distribution) as parameters to follow the efficiency. The treatment objective was to remove particles >20 microm, in such conditions that the effluent can contain organic matter and nutrients necessary for crops with a reduced number of helminth ova (with sizes between 20 to 80 microm). Using the TSS as parameter, the best coagulation (460 s(-1), 60 s contact time and 300 micromolAl/L) and flocculation (20 s(-1) with 15 min) conditions produced an effluent with 1.2 HO/L. To obtain a similar results but using operating conditions determined with the PSD at a three times lower coagulant dose can be employed (diminishing operating costs and reducing the quantity of sludge produced), and a reduction on energy consumption of around eight times can be reached. Best operating conditions defined using the PSD (160 s(-1), 60 s contact time and 100 micromolAl/L) produced an effluent with <0.4 HO/L.

Agriculture↗

PubMed2006

Disinfection of sludge with high pathogenic content using silver and other compounds.

A physicochemical sludge with high microbial content (10(2)-10(4) FPU/g TS bacteriophages, 10(6)-10(7) MPN/g TS faecal coliforms, 10(4) MPN/g TS Salmonella spp., 10(4) MPN/g TS Shigella spp., 10(3) MPN/g TS Pseudomonas aeruginosa, 10(2) MPN/g TS Vibrio cholerae, 10(2)-10(3) cysts/g TS Giardia sp., 10(2)-10(4) oocyts/g TS Cryptosporidium sp., 168-215 viable helminth ova/g TS) was disinfected using silver, silver-copper, and silver-copper plus a synergistic agent (SA). Twenty milligrams Ag/g TS inactivated 4.8 log of faecal coliforms in 1 h; however, 40 mg Ag/g TS are needed to reduce helminth ova viability from 84 to 38.4% in the same period of time. Combinations of Ag-Cu (60:600 mg Ag-Cu/g TS) and Ag-SA (60:24 mg Ag-SA/g TS) inactivated 7.8 log of faecal coliforms and around 90% of helminth ova in 60 min. To produce USEPA class A biosolids, 10:100:8 and 5:50:13.3 mg Ag-Cu-SA/gTS are needed. Bacterial regrowth was not observed for all conditions producing <1000 MPN/gTS faecal coliforms, suggesting a residual disinfection effect. Recommended doses to produce class A biosolids inactivated 2-4 log of bacteriophages, 4 log of Salmonella spp., 4 log of Shigella spp., 3 log of Pseudomonas aeruginosa, 2 log of Vibrio cholerae, 87-99.9% of Giardia sp., and 75-99.9% of Cryptosporidium sp.

Animals↗

PubMed2006

Comparison of techniques for the detection of helminth ova in drinking water and wastewater.

Many countries use wastewater for irrigation. The World Health Organization established, as reuse guidelines, a maximum value of 1 helminth ovum/L for irrigation. Various techniques for enumerating helminth ova in water have been published. To determine the most adequate method for Mexico, four techniques were compared: the U.S. Environmental Protection Agency (U.S. EPA), membrane-filter, Leeds I, and Faust. Two types of water were used: drinking water and municipal wastewater effluent. Sensitivity, discrimination coefficients, precision, recovery efficiency, and cost were determined. In addition, several unseeded wastewater samples were analyzed. For drinking water, U.S. EPA and the membrane-filter techniques demonstrated comparable results; however, when wastewater was used, the membrane technique showed some deficiencies. Because the U.S. EPA technique may be used for samples with both high and low solids content, allows for the recovery of helminth ova with different specific gravities, and has the lowest total cost, it was selected as the best technique.

Agriculture↗

PubMed2004

Particle size distribution as a useful tool for microbial detection.

Worldwide, raw or treated wastewater is used for irrigation. However, this practice implies that the microbial content must be controlled. Unfortunately, detection techniques for microorganisms are costly, time consuming, and require highly trained personnel. For these reasons, this study used particle size distribution to measure the microbial quality of wastewater through correlations between the number or volume of particles and the concentration of fecal coliforms, Salmonella spp. and helminth ova. Such correlations were obtained for both raw and chemically treated wastewater. The best fit was the one for helminth ova, which applies for both the influent and effluent and also for all the coagulants involved. This technique allows the on-line quantification of helminth ova at a cost of US$3 and it takes only 5 minutes, instead of the US$70 and 5 days for the standard technique. With respect to the coagulants applied, their behavior is different only for particles smaller than 8 microm, and thus this value is considered as the critical size for this particular treatment. The best coagulant was the aluminium polychloride. In addition, this work establishes the distribution of COD, TSS, nitrogen, and phosphorous for particles smaller and larger than 20 microm.

Agriculture↗

PubMed2004

Disinfection kinetics of pathogens in physicochemical sludge treated with ammonia.

Ammonia is a disinfectant which can diffuse through the membrane of highly resistant structures like helminth ova. Thus, it can be considered an alternative disinfectant of wastewater sludge with high pathogenic content. In this study, the kinetic parameters of the Hom model were used to describe the inactivation with ammonia of faecal coliforms, Salmonella spp. and viable helminth ova. These were obtained in processes considering the addition of ammonia alone as well as for ammonia combined with an increase in temperature. The sludge was sampled from a municipal wastewater treatment plant using an APT (Advanced Primary Treatment) or CEP (Chemical Enhanced Primary) process. With 20% w/w of ammonia, 7 logs of faecal coliforms, 6 logs of Salmonella spp., and 83% of viable helminth ova were reduced in 2 hours contact time. To eliminate 100% of the helminth ova from samples having 88-132 ova/g TS it was needed to combine 20% of ammonia with 50 degrees C. The analysis of parameters k, n and m indicate higher resistance to inactivation of helminth ova compared to bacteria and a better performance of the ammonia process than lime stabilization to inactivate microorganisms. In addition, ammonia increased the agricultural value of the biosolids produced.

Ammonia↗

PubMed2002

Comparison of the quantity and quality of the microbiological content of sludge in countries with low and high content of pathogens.

The parasites present in the residual sludge generate by the diverse treatment processes of residual water vary, depending on the socioeconomic and epidemiological conditions of different communities. And although data exist at the global level regarding the microbiological quality of sludge, these data are practically nonexistent in developing countries. Therefore, this project compares the content of the four principal groups of parasites in residual sludge from the United States and Mexico. The marked differences between the orders of magnitude found in the two countries (coliphages 10(3)-10(6) and 1.3 x 10(5) PFU/gTS, fecal coliforms 10(7)-10(10) and 10(7), Salmonella typhi 10(6)-10(8) and 10(3) MPN/gTS, Giardia lamblia 10(2)-10(4) and 10(2) cysts/gTS and helminth ova from 73-177 and <1 to 10 viable HO/gTS, respectively) will permit proposing real, effective and economical stabilization processes (undoubtedly different from those of industrialized countries), and will thus take advantage of the benefits represented by the reuse and disposal of sludge, in addition to developing regulations in agreement with the conditions of each region.

Animals↗

PubMed2001

Removal of microorganisms in different stages of wastewater treatment for Mexico City.

In this study the removal of a diversity of microorganisms during different stages of treatment was evaluated. The process scheme consisted of Advanced Primary Treatment (APT), sand filtration, and chlorine disinfection. During the first 2 stages, fecal coliforms were reduced from 1.24 x 10(9) to 1.2 x 10(8) MPN/100 mL and helminth ova were reduced to less than 1 ova/L. Nevertheless, to obtain an effluent water quality that meets the microbiological standards recommended by the World Health Organization (1989) and the Mexican norm for water destined for agricultural reuse it was necessary to disinfect the effluent with a chlorine dose of 12 mg/L for a 3 hour contact time. Under these conditions, fecal coliforms were reduced from 1.2 x 10(9) to 5.8 x 10(1) MPN/100 mL, Salmonella spp. from 5.0 x 10(8) MPN/100 mL to below the detection limit, Pseudomonas aeruginosa from 2.0 x 10(5) MPN/100 mL to below the detection limit, and protozoan cysts from 1052 to 31 cysts/L. Regrowth of bacteria was never observed during the 48 hours period following disinfection. The active chlorine was primarily in the form of chloramines thus reducing the formation of other potentially carcinogenic disinfection byproducts.

Chlorine↗