Suchergebnisse

Phosphorus is an essential nutrient for growth in all living organisms and is used as fertilizer to maintain food production. Today's recovery of mineral phosphate will lead to a lack of phos-phorus as mineral fertilizer since phosphorus will become more expensive over the time. In-creased awareness that the mineral phosphate is not a renewable resource means that recycling of phosphorus is an important environmental and food safety issue. In the given thesis, the recovery of phosphorus was carried out by the precipitation of the am-monium-magnesium-phosphate (struvite) complex. The overriding purpose was to determine the optimal parameters for phosphates removal through the struvite precipitation from the re-ject- and sludge- wastewater after the biological treatment from the HIAS sewage plant in Hamar, Norway. Furthermore, the goal was to achieve a struvite with the high nutrients content and use it as a potential fertilizer. To accomplish that goal it was formed hypotheses, made the experiments, analysis, and results. Based on the theory, three hypotheses were formed, which are focused on varying the parame-ters time, pH and molar ratio of Mg2+: NH4+. Firstly, an increase in pH from 8 to 8.3 should increase phosphorus removal through struvite precipitation. Secondly, the reaction time plays role in phosphorus recovery. Thus, the reaction time in the interval 20 to 60 min should be optimal for struvite formation with the high P-recovery. Thirdly, the molar ratio of Mg2+: NH4+ at 1.2: 10 and 1.5: 10: should cause about 95% of P removal. Finally, the concentration of toxic elements, such as heavy metals, was expected to meet the legislations requirements after the experiments. To carry out the experiments, two sources of wastewater have been taken from the HIAS, mixed and added the salt of magnesium. The solution has been mixed and centrifuged. Both the liquid part and the sediment (struvite) have been analyzed. The struvite was weighted and analyzed iv on the content of elements. The liquid part was analyzed on phosphorus and ammonium recov-ery, turbidity, conductivity and the content of elements. The results showed the highest phosphorus recovery of 97% was achieved by the Mg2+: NH4+ molar ratio of 1.5:10 and the pH 8.3, which looks like the optimum combination for PO43- re-covery. All the experiments showed the same ammonium recovery, at about 68.5%. 20 min reaction time showed better struvite removal than at 60 min. It was found that, although, the amount of struvite sedimentation was small, the quality of precipitated struvite was high. The struvite contains a very low number of toxic elements, which are less than in the legislations requirements. The results showed that the Mg2+: NH4+ molar ratio and the pH plays key role in enhancing of phosphorus recovery through struvite precipitation. Moreover, the changing in time also can affect the quality of struvite as a future fertilizer. ; M-MINA

Phosphorus (P) is becoming a scarce element due to the decreasing availability of primary sources. Therefore, recover P from secondary sources, e.g. waste streams, have become extremely important. Sewage sludge ash (SSA) is a reliable secondary source of P. The use of SSAs as a direct fertilizer has very restricted legislation due to the presence of inorganic contaminants. Furthermore, the P present in SSAs is not in a plant-available form. The electrodialytic (ED) process is one of the methods under development to recover P and simultaneously remove heavy metals. The present work aimed to optimize the P recovery through a 2 compartment electrodialytic cell. The research was divided in three independent phases. In the first phase, ED experiments were carried out for two SSAs from different seasons, varying the duration of the ED process (2, 4, 6 and 9 days). During the ED treatment the SSA was suspended in distilled water in the anolyte, which was separated from the catholyte by a cation exchange membrane. From both ashes 90% of P was successfully extracted after 6 days of treatment. Regarding the heavy metals removal, one of the SSAs had a better removal than the other. Therefore, it was possible to conclude that SSAs from different seasons can be submitted to ED process under the same parameters. In the second phase, the two SSAs were exposed to humidity and air prior to ED, in order to carbonate them. Although this procedure was not successful, ED experiments were carried out varying the duration of the treatment (2 and 6 days) and the period of air exposure that SSAs were submitted to (7, 14 and 30 days). After 6 days of treatment and 30 days of air exposure, 90% of phosphorus was successfully extracted from both ashes. No differences were identified between carbonated and non-carbonated SSAs. Thus, SSAs that were exposed to the air and humidity, e.g. SSAs stored for 30 days in an open deposit, can be treated under the same parameters as the SSAs directly collected from the incineration process. In the third phase, ED experiments were carried out during 6 days varying the stirring time (0, 1, 2 and 4 h/day) in order to investigate if energy can be saved on the stirring process. After 6 days of treatment and 4 h/day stirring, 80% and 90% of P was successfully extracted from SSA-A and SSA-B, respectively. This value is very similar to the one obtained for 6 days of treatment stirring 24 h/day.

AbstractPolyphosphate accumulating fungi was cultured to remove and recover the excessive phosphorus from dairy manure wastewater (DMW). The microbial treatment removed 83.9% of phosphorus in 20‐fold diluted DMW by the fungal biomass in 12 h. At the meantime, 33.6% of chemical oxygen demand, 46.5% of total nitrogen, and 89.4% of total ammonia nitrogen were removed as well. At seventh reuse batch, the cells could still remove 50.4% of phosphorus from the diluted wastewater. The average phosphorus removal efficiency in seven reuse batches was calculated as 62.1%, the nitrogen‐to‐phosphorus ratio in DMW increased from 3.6 : 1 to 6.3 : 1. With the treatment, DMW will be more suitable for farmland irrigation, with the better nutritional ratio to support crop growth, and it will help mitigate phosphorus pollution to water bodies caused by over‐applied phosphorus in the farmland.

AbstractMunicipal digested sludge (MDS) has considerable phosphorus content that is between 1% and 15% in dry matter and it is a potential source for phosphorus recovery. A high amount of MDS is generated from sewage treatment plants in large cities and has many environmental concerns with its organic and inorganic constituents. In this study, phosphorus was recovered by precipitation with Ca(OH)2 and NaOH. Acid pretreatment was applied to MDS with H2SO4 and 58.7% of phosphorus was extracted from the solid phase to the liquid phase at pH 2. Up to 99% of dissolved phosphorus in the liquid phase was recovered with Ca(OH)2 and NaOH. Almost similar phosphorus precipitation rates were achieved with both bases but higher phosphorus contents (17% as P2O5) in precipitates were obtained by NaOH. The product obtained in this study can serve as a high‐quality raw material substitute for the low‐grade phosphate rocks (<15% P2O5) commonly utilized in the phosphate industry. Furthermore, this research presents a practical, environmentally friendly and cost‐effective approach for sustainable sludge management and phosphorus production.