Phosphorus Recovery from Sewage Sludge Using Acidithiobacilli.

Sewage sludge contains a significant amount of phosphorus (P), which could be recycled to address the global demand for this non-renewable, important plant nutrient. The P in sludge can be solubilized and recovered so that it can be recycled when needed. This study investigated the P solubilization from sewage sludge using Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans. The experiment was conducted by mixing 10 mL of sewage sludge with 90 mL of different water/liquid medium/inoculum and incubated at 30 °C. The experiment was conducted in three semi-continuous phases by replacing 10% of the mixed incubated medium with fresh sewage sludge. In addition, 10 g/L elemental sulfur (S) was supplemented into the medium in the third phase. The pH of the A. thiooxidans and A. ferrooxidans treated sludge solutions was between 2.2 and 6.3 until day 42. In phase 3, after supplementing with S, the pH of A. thiooxidans treated sludge was reduced to 0.9, which solubilized and extracted 92% of P. We found that acidithiobacilli supplemented with S can be used to treat sludge, i.e., achieve hygienization, removal of heavy metals, and solubilization and recovery of P.

Recovery of nitrogen and phosphorus from human urine using membrane and precipitation process.

The nitrogen (N) and phosphorus (P) contents in human urine have been recovered using struvite precipitation and N-stripping techniques. Struvite precipitation technique recovers mainly phosphorus whereas N-stripping technique only recovers nitrogen. In this study, we developed an NPharvest technique which recovered both nitrogen and phosphorus separately in the same process, enabling their use independently. The technique used Ca(OH)2 to increase the pH of urine converting ammonium into NH3 gas and simultaneously precipitating P with Ca. The NH3 gas is passed through a gas permeable hydrophobic membrane (GPHM) and reacts with H2SO4 forming ammonium sulfate. Our result showed that more than 98% (w/w) of N and P can be harvested from urine in 8 h at 30 °C. The harvested ammonium sulfate contained 19% (w/w) N, and the sediment contained 1-2% (w/w) P. The extraction of N and P from 1 m3 of urine could give a profit of 1.5 €.

Reduction of phosphorus, nitrogen and microorganisms in pilot scale sand filter beds containing biotite, treating primary wastewater.

In sparsely populated areas, sand filter beds play an important role in wastewater treatment. As the need to improve the removal of nutrients increases, reactive filter materials represent one potential way to improve the reliability of current systems. We tested a pilot-scale multi-layer biotite filter for its ability to remove phosphorus, nitrogen, organic matter and enteric microorganisms with the importance of each layer in a multi-layer biotite filter being examined. In the experimental setup, the filters were fed with a raw wastewater influent mimicking the usual daily rhythm of water consumption and the reduction effects of the variable loads were examined during the experiment time of 54 weeks. It was observed that the reduction efficiency of the phosphorus was good (87%) during normal and under loading sequences but the reduction achieved for nitrogen was poor (27%). During and after overloading sequences, the phosphorus reduction was poor (46.5%) whereas the nitrogen reduction improved (to 66.7%). The reduction of organic matter was good during all sequences. The reductions of enteric microorganisms were at a level of 2-3 log10 units already after a single sand layer. For Escherichia coli, reductions of more than 5 log10 units were found after the wastewater had passed through a multilayer biotite filter during all sequences. It is concluded that the inclusion of a biotite layer improves the reliability of the filter bed. However, the proper scaling of the unit is essential in order to guarantee that the filter remains in aerobic conditions.

Maturity and hygiene quality of composts and hygiene indicators in agricultural soil fertilised with municipal waste or manure compost.

Composts produced from municipal source separated biowaste (Biowaste), a mixture of biowaste and anaerobically digested sewage sludge (Biosludge) and cattle manure (Manure) were examined for their maturity and hygiene quality. The composts were applied to a potato crop in 2004 and to a barley nurse crop of forage ley in 2005 in a field experiment. Numbers of faecal coliforms, enterococci, clostridia and Salmonella in field soil were determined 2 weeks and 16 weeks after compost applications. Municipal compost batches chosen based on successful processing showed variable maturity during field application, and the need to evaluate compost maturity with multiple variables was confirmed. The numbers of faecal coliform were similar in all compost types, averaging 4.7 and 2.3 log( 10) CFU g(-1) in the first and second years, respectively. The highest number of enterococci was 5.2 log(10) CFU g(-1), found in Manure compost in the first year, while the highest clostridia numbers were found in Biosludge compost, averaging 4.0 log(10) CFU g(-1) over both years. Except for one case, less than 2.4 log(10) CFU g(-1) of faecal coliforms or clostridia were found in compost-fertilised soil, while the numbers of enterococci were mostly higher than in unfertilised soil (<4.2 or <3.2 log(10) CFU g(-1), respectively). No hygiene indicator bacteria were present in compost-fertilised potato at harvest. Overall, compost fertilisations caused rather small changes in the counts of hygiene indicators in the field environment.

Human urine and wood ash as plant nutrients for red beet (Beta vulgaris) cultivation: impacts on yield quality.

The objective of this study was to evaluate the effect of human urine and wood ash fertilization on the yield and quality of red beet by measuring the microbial, nutrient, and antioxidant (betanin) content of the roots. Red beets were fertilized with 133 kg of N/ha as mineral fertilizer, urine and ash, and only urine with no fertilizer as a control. The mineral-fertilized plants and urine- and ash-fertilized plants also received 89 kg of P/ha. Urine and ash and only urine fertilizer produced 1720 and 656 kg/ha more root biomass, respectively, versus what was obtained from the mineral fertilizer. Few fecal coliforms and coliphage were detected in mineral-fertilized and urine- and ash-fertilized red beet roots. The protein and betanin contents in red beet roots were similar in all treatments. In conclusion, this study revealed that urine with or without ash can increase the yield of red beet and furthermore the microbial quality and chemical quality were similar to the situation in mineral-fertilized products.

Stored human urine supplemented with wood ash as fertilizer in tomato (Solanum lycopersicum) cultivation and its impacts on fruit yield and quality.

This study evaluates the use of human urine and wood ash as fertilizers for tomato cultivation in a greenhouse. Tomatoes were cultivated in pots and treated with 135 kg of N/ha applied as mineral fertilizer, urine + ash, urine only, and control (no fertilization). The urine fertilized plants produced equal amounts of tomato fruits as mineral fertilized plants and 4.2 times more fruits than nonfertilized plants. The levels of lycopene were similar in tomato fruits from all fertilization treatments, but the amount of soluble sugars was lower and Cl(-) was higher in urine + ash fertilized tomato fruits. The beta-carotene content was greater and the NO(3)(-) content was lower in urine fertilized tomato fruits. No enteric indicator microorganisms were detected in any tomato fruits. The results suggest that urine with/without wood ash can be used as a substitute for mineral fertilizer to increase the yields of tomato without posing any microbial or chemical risks.

Evaluating slurry broadcasting and injection to ley for phosphorus losses and fecal microorganisms in surface runoff.

The recent growth in the size of dairy cattle farms and the concentration of farms into smaller areas in Finland may increase local water pollution due to increased manure production and slurry application to grass. Therefore, a field study was conducted to monitor losses of total phosphorus (TP), dissolved reactive phosphorus (DRP), and fecal microorganisms in surface runoff from a perennial ley. Cattle slurry was added once a year in June 1996-1997 (Study I) and biannually in June and October 1998-2000 (Study II). The slurry was surface broadcast or injected into the clay soil. The field had a slope of 0.9 to 1.7%. Mineral fertilizer was applied on control plots. Biannual slurry broadcasting increased DRP (p < 0.001) and TP losses (p < 0.001) and numbers of fecal microorganisms in surface runoff waters. The highest losses of TP (2.7 kg ha(-1) yr(-1)) and DRP (2.2 kg ha(-1) yr(-1)) and the highest numbers of fecal coliforms (880 colony-forming units [CFU] per 100 mL) and somatic coliphages (2700 plaque-forming units [PFU] per 100 mL) were measured after broadcasting slurry to wet soil followed by rainfall in fall 1998. Injection reduced the TP and DRP losses in surface runoff by 79 and 86%, respectively, compared with broadcasting (17 Oct. 1998-27 Oct. 1999). Corresponding numbers for fecal coliforms were 350 CFU (100 mL)(-1) and for somatic coliphages were 110 PFU (100 mL)(-1) in surface runoff after injection in October 1998. Slurry injection should be favored when spreading slurry amendments to grassland to avoid losses of P and fecal microorganisms in runoff to surface waters.

Elimination of enteric bacteria in biological-chemical wastewater treatment and tertiary filtration units.

The occurrence and removal of salmonellae and faecal indicators in four conventional municipal wastewater treatment plants (MWTP) were investigated. In addition, we tested the efficiency of a semi-technical scale biological nutrient removal process and three pilot-scale tertiary filtration units in microbial removal. All influent samples collected from MWTPs contained salmonellae from 93 to 11,000 MPN/100 ml and indicator bacteria from about 10(7) to 10(8) CFU/100 ml. The reductions in salmonella numbers achieved in full-scale biological-chemical wastewater treatment and semi-technical scale biological nutrient removal processes were usually between 94% and virtually 100% (99.9%) and indicator bacteria reductions between 2 and 3 log units. Microbial numbers in MWTP effluents could be modelled as a function of effluent residual organic matter, suspended solids and total phosphorus concentrations. Pilot-scale tertiary treatment by rapid sand contact filter, chemical contact filter and biological-chemical contact filter reduced salmonella numbers below the detection limit and faecal coliform numbers on average by 99%, 39% and 71%, respectively. A total of 32 Salmonella serovars were identified among 197 Salmonella isolates from municipal wastewaters. Of the isolates, 32% were resistant to nalidixic acid, indicating reduced sensitivity to ciprofloxacin, the drug of choice in the treatment of salmonellosis. In addition, 18% of the isolates were multiresistant. Our results, especially antibiotic resistant Salmonella strains, indicate that conventional municipal wastewater treatment without efficient tertiary treatment, like filtration or disinfection, may constitute a risk for public health.