| 1. |
- Cohen, Yariv
(författare)
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Phosphorus dissolution from ash of incinerated sewage sludge and animal carcasses using sulphuric acid
- 2009
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Ingår i: Environmental Technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 30, s. 1215-1226
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Tidskriftsartikel (refereegranskat)abstract
- Large amounts of phosphorus are present in organic waste, mainly in sewage sludge and animal by-products. Increasingly, the waste is incinerated and phosphorus ends up in the ash. Sustainable waste management requires the beneficial reuse of phosphorus present in such ash. The first necessary step when recovering phosphorus from ash is dissolution by acid. The objective of this study was to quantify the acid requirement for phosphorus dissolution from sewage sludge ash and animal carcass ash. Both the amount of acid applied and its concentration were varied. Furthermore, phosphorus dissolution was optimized by controlling the pH during acid addition. Elemental analysis of sewage sludge ash showed that it comprised 6-10% P, 7-18% Ca, 2-11% Fe and 3-9% Al. The elemental content of animal carcass ash was even higher: 18% P and 30% Ca. The amount of acid required to obtain 85% phosphorus dissolution from sludge ash was 0.39-0.78 kg H2SO4 kg-1 ash, depending on the total cation/phosphorus equivalent ratio. The amount required to obtain the highest possible P dissolution within two hours (73%) from animal carcass ash was 0.69 kg H2SO4 kg-1 ash. Lower amounts of sulphuric acid were required for P dissolution in ashes of sludge from a bio-P treatment process and animal carcass, compared with the theoretical acid requirement for apatite dissolution. Applying pH control during dissolution resulted in reduced acid consumption (20%) and enabled more than 85% phosphorus dissolution from sludge ash at pH 2.0 in the two-hour dissolution time.
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| 2. |
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| 3. |
- Govindarajan, Venkatesh, 1972-, et al.
(författare)
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Changes in material flows, treatment efficiencies and shifting of environmental loads in the wastewater treatment sector. : Part I: Case study of the Netherlands
- 2009
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Ingår i: Environmental technology. - : Taylor & Francis. - 0959-3330 .- 1479-487X. ; 30:11, s. 1111-1129
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Tidskriftsartikel (refereegranskat)abstract
- The material that is separated from wastewater in wastewater treatment plants has to be transferred from the water phase to the atmosphere, lithosphere, and/or biosphere (and also the technosphere). After the initial discharges into the different environmental media (and the technosphere), there are further 'inter-sphere' leakages or redirections. However, these happen over protracted periods of time and have not been accounted for in this paper. The paper presents a case study on the wastewater treatment plants in the Netherlands, examines how the degree of separation of COD (BOD), nitrogen, phosphorus and heavy metals from the wastewater have increased over time, and studies the changes in proportions separated out to the atmosphere and lithosphere. The hydrosphere has benefited from a decline in the degree of eutrophication and marine/fresh water toxicity, owing to the favourable combination of higher degrees of separation, over time, and source control, especially in the industrial sector. Global warming is a major concern owing to the increasing conversion of COD to carbon dioxide (and methane). Heavy metal and nitrogen emissions have been curbed thanks to source reduction within industries. Technologies have, of course, enabled some mitigation of the problems associated with atmospheric (global warming and toxicity) and lithospheric (toxicity) pollution, though these are beyond the scope of this paper, which assumes a hypothetical worst-case scenario in this regard for the study period 1993-2005.
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| 4. |
- Hagman, Marinette, et al.
(författare)
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Advanced oxidation of refractory organics in leachate--potential methods and evaluation of biodegradability of the remaining substrate.
- 2008
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Ingår i: Environmental Technology. - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 29:9, s. 941-946
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Tidskriftsartikel (refereegranskat)abstract
- An assessment of potential methods suitable for degradation and/or reduction of refractory organics was performed on landfill leachate from SYSAV AB, Malmö, Sweden. Pretreatment of the leachate was performed in a sequence batch reactor designed for nitrification in activated sludge. Oxidation of the leachate was then O3, O3/pH adjustment (pH 9 and 10), H2O2, O3/H2O2 and performic acid in lab-scale reactors. The degradation of organic material was followed with chemical oxygen demand (COD) measurements for all experiments except for the performic acid treatment for which total organic carbon (TOC) measurements were used. The potential degradation of refractory organics into biodegradable organic material was analysed by subsequent oxygen uptake rate (OUR) measurements in laboratory batch reactors. Ozonation of biologically pre-treated leachate increased reduction of the organic material. The most biodegradable organic material was produced after oxidation with only ozone and ozonation at pH 9. Performic acid did not reduce the content of organic material in the leachate. However, a combination of biological pretreatment, chemical oxidation with O3/H2O2 and a subsequent biological process resulted in the most efficient oxidation method for the tested leachate.
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| 5. |
- Hallberg, Magnus, et al.
(författare)
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Assessment of suspended solids concentration in highway runoff and its treatment implication
- 2006
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 27:9, s. 945-950
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Tidskriftsartikel (refereegranskat)abstract
- It is understood that the major pollution from storm water is related to the content of particulate matter. One treatment practice is based on the first flush, i.e. detention of the initial part of the runoff that is considered to contain the highest concentrations of pollutants, This study has evaluated the concentration of total suspended solids in 30 consecutive runoff events during the winter season for an area of 6.7 hectares. A six-lane highway (E4) that has an annual average daily traffic load of 120,000 dominates the area and road de-icing salt (NaCl) and studded tires were in regular use during the studied period. The effluent standard for wastewater of 60 mg TSS per litre applied in EU was used to assess the treatment requirement of storm water. In only two of the events the event mean concentration was below 60 mg V. In four runoff events a partial event mean concentration below 60 mg l(-1) was found, in 26 %, 12 %, 11 %, and 2 % respectively of the runoff volume. This would suggest that a capture of the initial part of the runoff for subsequent treatment is less applicable in this type of urban watershed.
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| 6. |
- Hedström, Annelie
(författare)
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Wollastonite as reactive filter medium for sorption of wastewater ammonium and phosphorus
- 2006
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 27:7, s. 801-809
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Tidskriftsartikel (refereegranskat)abstract
- The utilisation of reactive filter media to remove ammonium and phosphorus can improve the effluent water quality of wastewater treatment systems. The objective of this study was to estimate the ammonium and phosphorus sorption capacity of wollastonite, a calcium meta silicate (CaSiO3) that is distributed worldwide. Phosphorus sorption mechanisms were also investigated. Batch sorption experiments with agitating bottles were carried out and both phosphate and ammonium solutions as well as wastewater were used. The results showed minor ammonium adsorption, with only 3-15% of the ammonium in the solutions being adsorbed to the wollastonite. Neither the reaction time (0.5-20 h) nor the initial concentrations of phosphorus and ammonium (11-114 mg l(-1) NH4-N) were of importance. For high initial phosphate concentrations, phosphate was greatly adsorbed to the wollastonite (850 mg kg(-1) at an initial phosphate concentration of 61 mg l(-1) PO4-P). However, phosphate sorption was minor when the initial phosphate concentration was low. This study showed that sorption reactions were important when phosphate was removed by wollastonite, and indicated precipitation of phosphate on the wollastonite surfaces as one possible mechanism for phosphate retention. The results from this study indicated that the wollastonite investigated may not be suitable for municipal wastewater treatment applications due to the low phosphorus sorption capacity for low initial phosphorus concentrations.
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| 7. |
- Jeppsson, M., et al.
(författare)
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The effect of silver ions and chlorine on the survival of Staphylococcus aureus and Bacillus cereus in dishwater
- 2007
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Ingår i: Environmental Technology. - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 28:12, s. 1419-1427
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the effect of chlorine and silver ion solutions on the survival of Bacillus cereus (vegetative phase) and Staphylococcus aureus in batch cultures, representing dishwater. Dishwater contains organic matter and bacteria and bacterial activities are partly reduced by high pH (11-12) and temperature (55-65 degrees C) in professional and domestic dishwashers. in manual dishwashing, temperature and pH are kept lower (45 degrees C and pH 7), which is less sufficient for the reduction of bacteria. In a broth, organic loaded in order to mimic dishwater, solutions of Ag+ or hypochlorite were added at 45 degrees C and pH 7 and samples were withdrawn for a period of 40 minutes. 1 ppm Ag+ was required to obtain a 1 to 2 log unit reduction of B. cereus and S. aureus in 10 minutes. An addition of 160 ppm hypochlorite reduced B. cereus and S. aureus by 4 log units in two minutes, whereas 16 ppm of hypochlorite had no effect on the survival of S. aureus. The level of free residual chlorine varied with the COD value of the cultured solutions. We found that both silver and hypochlorite can be used as antibacterial agents in dishwater. The disadvantage with the use of hypochlorite is that the COD value determines the antibacterial effect. Using Ag+ solutions to reduce bacteria has the drawback that they are toxic to water-living organisms and are considered to develop Ag+ resistant bacteria. To reduce the risk of cross-contamination from dishwater to dishware high temperature and detergent with high pH is to be preferred.
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| 8. |
- Kriipsalu, Mait, et al.
(författare)
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Fate of polycyclic aromatic hydrocarbons during composting of oily sludge
- 2008
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 29:1, s. 43-53
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the effectiveness of aerobic degradation with emphasis on the 16 U.S. EPA priority polycyclic aromatic hydrocarbons (PAH), oily sludge generated by a dissolved air flotation flocculation unit of a wastewater treatment plant in a petroleum refinery was amended with remediated oil‐contaminated soil and non‐mature garden waste compost 40:40:20 (wet weight) respectively. About 21 t of the mixture with a top‐layer formed by 30 cm of remediated soil was treated in a 28 m3 air‐forced reactor. The PAH concentration was monitored for 370 days. In the top‐layer, a reduction of 88 % of the total extractable PAH was measured at day 62 and a final reduction of 93 % at day 370 days. In the mixture, a reduction of 72 % in total PAH was measured at day 62, followed by fluctuation in concentration with a final measured reduction of 53 % at day 370. The analysis of individual PAH in the mixture suggested that volatilization and biodegradation are the main mechanisms responsible for the reduction of 2 ring PAH and 3–4 ring PAH, respectively. Fluctuation of 5–6 ring PAH concentrations with increase observed at the end of the period might result from a combination of the following: (i) sequestration of large PAH in the organic matrix (reducing bioavailability, biodegradability and eventually, extractability) and desorption as composting progresses; (ii) heterogeneous distribution of the stable large PAH in the mixture, thus affecting sampling. It was concluded that one‐time composting in static‐aerated biopiles with organic amendments as the sole strategy to treat oily sludge is very effective in reducing the content of 2–4 ring PAH, but it is not effective in reducing the content of 5–6 ring PAHs, even after a relatively long time span (370 d). The concentrations measured in the remediated soil that formed the top layer after 62 days of composting suggests that further relevant reduction of residual PAH (89% of total PAH and 69% of 5–6 ring PAH) can be obtained if the contaminated masses are exposed to a second thermophilic phase. This could be achieved by adding new easily biodegradable organic amendments to the contaminated masses after some months of composting, remixing and composting again for a minimum additional period of 2 months.
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| 9. |
- Larsdotter, Karin, et al.
(författare)
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Biologically mediated phosphorus precipitation in wastewater treatment with microalgae
- 2007
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 28:9, s. 953-960
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Tidskriftsartikel (refereegranskat)abstract
- A lab-scale continuous microalgal culture was grown on sterile-filtered wastewater in order to clarify the phosphorus removing mechanisms in a microalgal treatment step that treats residual phosphorus from a hydroponic wastewater treatment pilot plant. The phosphorus assimilation was dependent on algal biomass production, whereas the chemical precipitation was dependent on phosphorus load, i.e. an increase in average precipitation rate with decreased hydraulic retention time was observed. The chemical precipitation was mainly a result of the increased pH, which was biologically mediated by the photosynthesising algae. The precipitate was composed of a calcium phosphate with magnesium included, magnesium hydroxide and calcite. A significant nitrogen removal was also experienced, which implies that the microalgal wastewater treatment is appropriate both for phosphorus and nitrogen removal.
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| 10. |
- Marobhe, Nancy, et al.
(författare)
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Simple and rapid methods for purification and characterization of active coagulants from the seeds of Vigna unguiculata and Parkinsonia aculeata
- 2007
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 28:6, s. 671-681
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Tidskriftsartikel (refereegranskat)abstract
- The coagulating properties of aqueous crude extracts and purified proteins of Vigna unguicilata and Parkinsomia aculeata seeds, which are traditional water coagulants in rural areas of Tanzania, were studied. The coagulation activity assays were done using one millilitre (ml) of kaolin water samples. Coagulating proteins were purified in two-step ion exchange chromatography. The properties of coagulant protein were compared with Moringa oleifera. Coagulating components eluted by 0.6 M NaCl in both coagulants are cationic proteins that have the molecular mass of about 6 kDa, which is very similar to that of M. oleifera. The proteins of V. unguiculata and P. aculeata eluted by 0.3 M NaCl also harbour coagulation activity but proteins eluted with 0.6 M NaCl have higher activity. The dosage for coagulation using purified proteins of both coagulants is about 5 to 10 times lower than that of crude seed extracts. The optimum floc settling time of water treated by crude seed extracts and purified proteins ranged between two and two and half hours. Coagulating proteins of both coagulants elated by 0.6 M NaCl are thermoresistant and retained coagulation activity of 87% to 92% after boiling for two hours at 80 degrees C and one hour at 95 degrees C. Thermotolerant proteins of V. unguiculata eluted by 0.6 M NaCl and P. aculeata have wider pH range of 5.5 to 8.5 for coagulation activity than those of M. oleifera proteins. The present investigation reveals the possibility of using purified natural coagulants for water treatment to produce safe drinking water.
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