Assessment of microbiota diversity in dental unit waterline contamination

Background Dental unit waterlines (DUWLs) provide water for handpieces, air/water syringes, and mouth-rinse water outlets. DUWL contamination can negatively affect the operating environment and public health. Therefore, it is important to elucidate the bacterial concentrations and microbial composition in the DUWLs from different dental specialties. Methods We collected 350 5-mL dental water samples (from high-speed handpieces, air/water syringes, and mouth-rinse water outlets) from 60 dental chair units (DCUs) at a dental hospital to determine the bacterial concentrations by culture methods. Meanwhile, to investigate the diversity and community structure of microbe in the DUWLs, 17 high-quality DNA from 60 250-mL air/water syringe water samples, which were collected from the same 60 DCUs, were analyzed using 16S rDNA high-throughput sequencing. Results The median bacterial concentration was 166 (31.5, 672.5) CFU/mL and the range was 0–3,816,000 CFU/mL. Only 42.6% of the water samples had bacterial concentrations below 100 CFU/mL. The Kruskal–Wallis H-test revealed that the water samples from three dental specialties had significantly different bacterial concentrations (H = 27.441, P < 0.01). High-throughput sequencing results showed significant differences in bacterial community structure between periodontics and the other two dental specialties. In the samples from three dental specialties, 508 OTUs were detected, with 160, 182 and 176 OTUs unique to the periodontics, endodontics and prosthodontics specialties, respectively. Linear discriminant analysis (LDA) effect size (LEfSe) suggested that Hydrocarboniphaga, Zoogloea, Aquabacterium, and Hydrogenophaga were enriched in the periodontics specialty; Acinetobacter, Geothrix, and Desulfovibrio were enriched in the prosthodontics specialty; and Alistipes, Clostridium XIVa, and Serratia were enriched in the endodontics specialty. Seven potentially human-pathogenic genera (Pseudomonas, Acinetobacter, Sphingomonas, Ochrobactrum, Rhizobium, Brevundimonas, and Methylobacterium) with relative abundance exceeding 1% were also detected in the DUWLs. Conclusions The bacterial concentrations and microbial composition were influenced by different dental specialties, so a validated disinfection protocol should be used to control DUWL contamination in different dental specialties.

Effects of Removal Conditions on Mercury Amount Remaining in the Oral Cavity and inside Drainage System after Removing Dental Amalgams

Mercury is produced and drained into the environment by removing dental amalgams, which may cause mercury pollution. This study aimed to clarify the mercury amount remaining in the oral cavity and inside the drain system after removal. The effects of the removal conditions and differences in drainage systems were also investigated. Dental amalgams filled in the tooth and placed in a phantom head were removed using an air turbine under several conditions (two removal methods, absence of cooling water, and intraoral suction). Then, the oral cavity was rinsed with 100 mL of water (oral rinse water), and 500 mL of water was suctioned to wash the inside of the drainage system (system rinse water). Both water samples were collected in two ways (amalgam separator and gas-liquid separator), and their mercury amounts were measured. It was found that the amount of mercury left in the oral cavity and drainage system after dental amalgams removal could be reduced when the amalgams were removed by being cut into fragments as well as using cooling water and intraoral suction. In addition, using amalgam separators can significantly reduce the amount of mercury in the discharge water and prevent the draining of mercury into the environment.

Indoor Hydroponics: A Potential Solution to Reuse Domestic Rinse Water

The objective of this study was to evaluate the potential of reusing domestic rinse water in an indoor hydroponic system and compare the growth pattern of Coleus plants using tap water and rinse water. A preliminary survey evaluatedthe knowledge about, home gardening, hydroponics, water usage and utility of rinse water in urban households. The experimental setup consisted of water culture hydroponic system with peat moss media. Data were collected and analyzed from 4 sample groups: Group A (tap water), B (tap water with NPK fertilizer), C (rinse water) and D (rinse water with NPK fertilizer) in a randomized experimental design (N=20) with five replicates.The study was conducted indoors in an urban household under controlled temperature (78ºF), light and humidity (60-70%). Parameters analyzed for assessment of plants growth included height (in millimeters), number of new leaves and leaf surface area. Environmental parameters including, pH and TDS (Total Dissolved Solids in parts per million) of the hydroponic solution, and pH and moisture of soil were also recorded. Descriptive statistical analysis and independent comparisons were done with a 95% assumed significance level (p<0.05).During the 20th, 25th and 30th day, plant height in Group A was significantly (p<0.05) higher than that of Group B and plant height in Group C was significantly higher than in Groups B and D.In terms of the environmental parameters, while rinse water had an alkaline pH, the addition of NPK fertilizer (Groups B and D) resulted in significantly lower pH.Based on the present study results, domestic rinse water can be reused as a successful alternative for tap water in indoor hydroponic cultivation of plants without the need for any additional fertilizer.

Purification of Cr(VI)-containing wastewater by chemical precipitation: test results of an experimental-industrial installation

We present the main results of experimental and industrial study of the developed process and pilot plant for purification of the Cr(VI)-containing rinse water by chemical precipitation. This technique implies full or partial return of treated water to rinse workpieces after chromium plating and prepare working solutions (precipitators). We characterize the manufacturing scheme of the pilot plant and the mode of its performance. Saturated aqueous solutions of Са(ОH)2 and Ва(ОH)2 were used as precipitating reagents. The tests confirmed the possibility of automatic dosing the reagents with due regard for the pH value of a medium, which can be used in both continuous and periodic rinsing. The operating conditions of rinsing the workpieces after electrochemical chromium plating were justified. We derived the equation for the calculation of the total salt content in the rinse water after its purification. We determined the duration of the rinsing without the need to renew the bath volume. The performed calculations substantiated the possibility of reducing the consumption of fresh water supplied for rinsing by the recycling of wastewater without deteriorating the quality of the rinsed workpieces. The reduction of water consumption by 35% was observed as compared with that stated by the regulations.

Wastewater Treatment from Galvanization Industry with Zinc recovery

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (<20 %), which makes Zn recovery not profitable. The experimental results presented in this article show that it is possible to use as a coagulant to treat the process wastewaters the spent pickling solution (SPS) from the process, kept separated and added with sodium hydroxide. This results in obtaining precipitates with Zn contents higher than 40%, which brings the further advantage of making Zn recovery profitable.

Chemical Selection for Flocculation of the Sludges Produced During Lime Neutralization of Acidic Spent Pickling Solutions and Rinse Water from Steel Pipe Mill

Acidic spent pickling solutions and rinse water are produced during steel pipe acid pickling. They are usually neutralised with lime in a neutralisation plant and pumped in the form of a wet sludge to a landfill. This is one of the main environmental issues of Russian steel mills. The implementation of sludge treatment units, including equipment for sludge polymer conditioning and dewatering, is an import consideration when seeking to reduce the impact of steel mills on human health and the environment. The researches results of polymer conditioning of the aggressive wastewater sludges by flocculants are reflected in the paper. Sludge samples were obtained from the neutralisation plant of an Ural’s steel pipe mill. Sludges of two types were investigated: the sludge which is formed in clarifiers during spent pickling solutions neutralization with lime and the sludge which is formed in clarifiers during rinse water neutralization with lime. During the work non-ionic, cationic, and anion flocculants Praestol® efficiency was estimated. The shortest time of water capillary suction from the flocculated sludge was accepted as efficiency criterion of flocculant processing. It was defined with use of the capillary suction timer Fann® and Whatman® 17 chromatographic paper. It is established that: non-ionic focculant Praestol® 2500 dose of 4–5 g/kg dry solids is effective for conditioning of the sludge produced during lime neutralization of acid spent pickling solutions; the anionic flocculant Praestol® 2540 dose of 1.5–2 g/kg dry solids is effective for conditioning of the sludge produced during lime neutralization of acid rinse water. The empirical response surfaces and the contour plots showing the relationship between capillary suction time and a dosage of flocculant and a charge density (% hydrolysis) of a flocculant were reveived. Keywords: steel pipe mill, acid pickling, wastewater, sludges, flocculants, capillary suction time

Prevalence and risk of staphylococcal and coliform carcass contamination of chickens slaughtered in the informal market in Gauteng, South Africa

PurposeThe primary objective was to determine the prevalence of indicator microorganisms [Staphylococcus aureus, non-S. aureus staphylococci (NSAS), coliforms and aerobic bacteria] for contamination of chicken carcasses, carcass drip and rinse water from the informal chicken market in Gauteng, South Africa.Design/methodology/approachChicken swabs, chicken drips and rinse waters were collected from 151 chickens from 47 random outlets. Pre-tested questionnaires were administered to capture the risk factors for bacterial contamination. Standard microbiological procedures were conducted for isolation and enumeration of target bacteria.FindingsNSAS (64% and 41%) and S. aureus (12% and 31%) were prevalent on carcasses and in carcass drip respectively. Coliforms (62%) and aerobic bacteria (85%) were detected in rinse water. Significant risk factors for contamination of carcasses with NSAS, S. aureus and coliform organisms were: evisceration of chickens on the same location used for sale, cleaning of display counter with dirty clothes/wipes, holding of differently sourced chickens in the same cage prior to slaughter, not cleaning the display table/counter and hands at all, washing knives in rinse water, high turnover of daily slaughter and length of time to display chickens.Research limitations/implicationsThe limitations of this research were the limited geographical coverage and small sample size.Practical implicationsThe isolation of these indicator microorganisms suggests the potential presence of other chicken-borne pathogens not tested for in the study.Social implicationsThe findings serve to inform policy on public health and street-vended food and can guide control on good sanitary practices.Originality/valueThis is the first comprehensive report on ready to eat chickens from the informal markets in Gauteng, South Africa.