Biological phosphorus removal from a phosphorus-rich dairy processing wastewater.

Dairy industry processing wastewaters consist mainly of dilutions of milk, milk products and cleaning solutions and, depending on the processes used, may be rich in phosphorus. In New Zealand and internationally, chemical removal of phosphorus is typically the phosphorus removal method of choice from dairy processing wastewaters. The enhanced biological phosphorus removal (EBPR) process was investigated in this study as an alternative phosphorus removal option using a continuous activated sludge system. A synthetic dairy processing wastewater was firstly subjected to fermentation in an anaerobic reactor (HRT = 12 hrs, pH = 6.5, temperature = 35 degrees C) resulting in a fermented wastewater with an average volatile fatty acid (VFA) concentration of 1055 mg COD/L. The activated sludge reactor was operated in an AO configuration with an HRT of 2.5 days and an SRT of 15 days. Stable EBPR was exhibited with 42 mg P/L removed, resulting in a final sludge phosphorus content of 4.9% mg P/mg TSS. In the anaerobic zone (HRT = 2.85 hrs) the sludge had a phosphorus content of 3.16% mg P/mg TSS and a poly-beta-hydroxyalkanoate (PHA) concentration of 86 mg COD/g TS.

Characterisation of aerobic bio treatment of meat plant effluent.

Primary treated meat processing plant effluent was characterised for the calibration of the ASM 2 model. The total COD of the wastewater was 500-2,000 mg L(-1). The wastewater contained 15-18% of RBCOD. RBCOD of the meat processing wastewater was from short chain fatty acids (SCFA). Acetic and iso-valeric acids contributed 50% of the total SCFA COD. The inert soluble and particulate COD fractions were each 4%. The COD exerted by carbohydrate was 5% of the total COD. Fat and protein contributed 51% and 44% of the total COD of the wastewater respectively. The average concentrations of ammonia, total phosphorus, total suspended solids and alkalinity were 75 mg L(-1), 34 mg L(-1), 450 mg L(-1) and 275 mg L(-1) CaCO3 respectively. Maximum specific growth rates of heterotrophs and autotrophs were between 1.2-2.5 day(-1) and 0.65-0.8 day(-1). The heterotrophs yield coefficient was 0.63 on a COD basis.

Enrichment of nitrifying microbial communities from shrimp farms and commercial inocula.

Nitrifying bacteria were selected from shrimp farm water and sediment ("natural" seed) in Thailand and from commercial seed cultures. The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs). Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/l and artificial wastewater containing 25 ppt salinity. The two SBRs were operated at a 7 d hydraulic retention time (HRT) for 77 d after which the HRT was reduced to 3.5 d. The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85% and 92% for the 7 d HRT and the 3.5 d HRT, respectively. The ammonia removals of microbial consortia from the commercial seed were 71% and 83% for these HRTs respectively. The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number (MPN) technique. Both AOB and NOB increased in number over the long-term operation of both SBRs. According to quantitative fluorescence in situ hybridisation (FISH) probing, AOB from the natural seed and commercial seed comprised 21 +/- 2% and 30 +/- 2%, respectively of all bacteria. NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources. Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures.

Bioleaching of metals from sludges and acid production under increased metal concentrations.

To remove heavy metals from sludge and slurries the heavy metals must first be solubilised. In this study, metal bioleaching using sulphuric acid producing microorganisms is investigated. The inhibitory effects of four metals (zinc, chromium, nickel and copper) on acid production were firstly assessed for concentrations of each metal up to 1,000 mg/l. Low concentrations of zinc and chromium (50 mg/L) appear to stimulate the production of sulphuric acid but concentrations of those metals at 500 mg/L and above inhibited acid production (20 to 30% of the control rate at a concentration of 1,000 mg/L). The average sulphuric acid production of the metal free control was 0.78 g/L/day over a 10 day period. At all concentrations of nickel and copper, sulphuric acid production was suppressed and was less than 10% of the control at 250 mg/L or more after 10 days. Activated sludge was also loaded with the four metals in individual bioleaching tests, in increments from zero up to 5,050 mg of metal/kg solids on a dry basis. In these bioleaching trials the sulphuric acid production averaged 0.9/g/L/day and the pH after 7 days was less than 2.0. Sludge copper concentrations of 3,850 and 5,050 mg/kg partially inhibited acid production (pH after 7 days was 2.4 and 2.7). The solubilisation for each metal after 7 days was Zn: 82-97%, Ni: 12-70%, Cu: 28-55%, and Cr: <20%. Bioleaching of a sludge loaded with a mixture of the four metals gave peak solubilities of 99% for Zn after 3 days, 68% for Ni after 6 days, 57% for Cu after 9 days and 33% for Cr after 9 days.

Biological nutrient removal from meat processing wastewater using a sequencing batch reactor.

Meat processing effluents are rich in nutrients (nitrogen: 75-200 mg L(-1) and phosphorus: 20-40 mg L(-1)) and COD (800-2,000 mg L(-1)) after primary treatment. A laboratory scale sequencing batch reactor (SBR) was operated for the treatment of a beef processing effluent from slaughtering and boning operations. An effective SBR cycle was found for removal of COD, nitrogen and phosphorus at 22 degrees C. The solid retention time was 15 days while the hydraulic retention time (HRT) was 2.5 days. The total nitrogen in the wastewater was reduced to less than 10 mg L(-1), while the total phosphorus decreased to less than 1.0 mg L(-1). The residual effluent soluble COD was found to be non-biodegradable as reflected by no further soluble COD removal following prolonged aeration. Removal of biodegradable soluble COD, ammonia nitrogen and soluble phosphate phosphorus of greater than 99% was achieved in the SBR. Good prediction of ammonia and nitrate nitrogen removal was obtained using IWA Activated Sludge Model. The operating cycle is shown to be appropriate to achieve simultaneous removal of COD and nutrients from the meat processing wastewater. Alkalinity and pH have an inverse relationship during the initial anaerobic and aerobic stages due to production and stripping of CO2. Use of a low level of DO in the final aerobic stage ensured complete ammonia removal and enhanced denitrification.

Inhibitory metabolites production by the cyanobacterium Fischerella muscicola.

Broad-spectrum inhibitory metabolites were produced by a benthic cyanobacterium Fischerella muscicola (UTEX 1829) in batch culture. These metabolites inhibited the growth of eukaryotic algae, cyanobacteria and eubacteria. The effect of culture age on the production and leakage of these inhibitory metabolites from the cyanobacterium was studied. Confirmation of the presence of an allelochemical, possibly fischerellin was achieved using high performance liquid chromatography (HPLC). The cyanobacterium produced inhibitory metabolites intracellularly at all stages of its growth cycle.