Achieving "Final Storage Quality" of municipal solid waste in pilot scale bioreactor landfills.

Entombed waste in current sanitary landfills will generate biogas and leachate when physical barriers fail in the future, allowing the intrusion of moisture into the waste mass contradicting the precepts of the sustainability concept. Bioreactor landfills are suggested as a sustainable option to achieve Final Storage Quality (FSQ) status of waste residues; however, it is not clear what characteristics the residues should have in order to stop operation and after-care monitoring schemes. An experiment was conducted to determine the feasibility to achieve FSQ status (Waste Acceptance Criteria of the European Landfill Directive) of residues in a pilot scale bioreactor landfill. The results of the leaching test were very encouraging due to their proximity to achieve the proposed stringent FSQ criterion after 2 years of operation. Furthermore, residues have the same characteristics of alternative waste stabilisation parameters (low BMP, BOD/COD ratio, VS content, SO4(2-)/Cl- ratio) established by other researchers. Mass balances showed that the bioreactor landfill simulator was capable of practically achieving biological stabilisation after 2 years of operation, while releasing approximately 45% of the total available (organic and inorganic) carbon and nitrogen into the liquid and gas phases.

The effect of hydraulic conditions on waste stabilisation in bioreactor landfill simulators.

Seven bioreactor landfill simulators (mixed gravel, gravel in layers, and controls without gravel with two levels of compaction, i.e. normal and lower density) were used to investigate the effect of different hydraulic conditions on the waste stabilisation process. The simulators with mixed gravel showed a higher degree of waste stabilisation towards the end of the experiment due to higher moisture content, whereas the other simulators were prone to clogging thus reducing the overall treatment effectiveness. Moreover, reaching neutral pH levels seemed to be the "driving force" that enhanced physical, chemical and biological processes contributing to waste stabilisation in the simulators with mixed gravel. After one year of operation, the residues of the different simulators were very close to achieve a final storage quality status comparable to the waste acceptance criteria for inert waste of the European landfill directive.

Alternative treatment for septic tank sludge: co-digestion with municipal solid waste in bioreactor landfill simulators.

Co-disposal of septic tank sludge had a positive effect on the municipal solid waste (MSW) stabilisation process in Bioreactor Landfill simulators. Co-disposal experiments were carried out using the Bioreactor Landfill approach aiming to solve the environmental problems caused by indiscriminate and inadequate disposal of MSW and especially of septic tank sludge. The simulator receiving septic tank sludge exhibited a 200 days shorter lag-phase as compared to the 350 days required by the control simulator to start the exponential biogas production. Additionally, the simulator with septic sludge apparently retained more moisture (>60% w/w), which enhanced the overall conversion of organic matter hence increasing the biogas production (0.60 m3 biogas kg(-1)VS(converted)) and removal efficiency of 60% for VS from the simulator. Alkaline pH values (pH>8.5) did not inhibit the biogas production; moreover it contributed to reduce partially the negative effects of NH(4)(+) (>2 g L(-1)) due to NH(3) volatilisation thus reducing the nitrogen content of the residues. Associated risks and hazards with septage disposal were practically eliminated as total coliform and faecal coliform contents were reduced by 99% and 100%, respectively at the end of the experiment. These results indicate that co-disposal has two direct benefits, including the safe and environmentally sound disposal of septic tank sludge and an improvement of the overall performance of the Bioreactor Landfill by increasing moisture retention and supplying a more acclimatised bacterial population.

Nitrification activities in full-scale treatment plants with varying salt loads.

The effect of salt on the nitrification activity in full-scale wastewater treatment plants (WWTP) was investigated. Not only the activity of ammonia and nitrite oxidisers was measured, but also the nitrifying population was assessed (by Fluorescent In Situ Hybridisation)--in full-scale domestic and industrial WWTPs, operated under various salt levels. The results demonstrate a decline in the activity of ammonia and nitrite oxidisers with an increase in salt content: the domestic WWTP with the lowest salt level (0.13g Cl- l(-1)) had the highest specific activity of ammonia and nitrite oxidisers (4.3 and 2.4 mg N (gVSS)(-1) h(-1), respectively), while the lowest specific activities of ammonia and nitrite oxidisers (1.1 and 0.5 mg N (gVSS)(-1) h(-1)) were measured at the highest NaCl concentration (16g Cl- l(-1)). However, comparing the nitrification activity of different types of sludge developed under different operational conditions with the reported values was not directly possible. So we have used the activated sludge model (ASM) to translate the routine operational data into parameters to enable the calculation of the actual fraction of nitrifiers and consequently the actual specific activity of ammonia and nitrite oxidisers. Expressing the activity of ammonia oxidisers in terms of actual specific activity makes the results from pure cultures, enriched cultures, pilot scale and full scale WWTPs comparable. Moreover, these results confirm the behaviour of nitrifiers under salt stress and validate the results obtained from pure and enriched cultures to be extrapolated to full scale.

Long term effects of salt on activity, population structure and floc characteristics in enriched bacterial cultures of nitrifiers.

The effect of salinity on the activity, the composition of nitrifiers and floc characteristics of nitrifying sludge was studied. Non-adapted and adapted (to 10g NaCl-Cl(-)/L for one year) enriched cultures of nitrifiers were tested in three sequencing batch reactors. Salt was increased gradually with 5 up to 40 g Cl(-)/L. No difference in steady state activity was observed between the adapted and non-adapted sludge. The activities of ammonia and nitrite oxidizers dropped 36% and 11%, respectively, at salt concentrations of 10 g Cl(-)/L. At 40 g Cl(-)/L inhibition reached 95% of salt free activity for ammonia and nitrite oxidizers in both adapted and non-adapted reactors. Nitrosomonas europaea and Nitrobacter sp. (fluorescent in situ hybridization) were the only nitrifiers present at high salt levels. Increased salt concentrations resulted in better settling characteristics of the nitrifying sludge. After 118 days the sludge was brought back to the initial conditions (0 g Cl(-)/L for non-adapted and 10 g Cl(-)/L for adapted). Despite the change in population composition similar kinetics as before the salt stress were observed.

Modelling nitrification, heterotrophic growth and predation in activated sludge.

A mathematical model describing the interaction between nitrifiers, heterotrophs and predators in wastewater treatment has been developed. The inclusion of a predation mechanism is a new addition to the existing activated sludge models. The developed model considered multi-substrate consumption and multi-species growth, maintenance and decay in a culture where nitrifiers, heterotrophs and predators (protozoa and metazoa) are coexisting. Two laboratory-scale sequenced batch reactors (SBRs) operated at different sludge retention time (SRT) of 30 and 100 days for a period of 4 years were used to calibrate and validate the model. Moreover, to assess the predator activity, a simple procedure was developed, based on measuring the respiration rate with and without the presence of the predators. The model successfully described the performance of two SBRs systems. The fraction of active biomass (ammonia oxidisers, nitrite oxidisers and heterotrophs) predicted by the proposed model was only 33% and 14% at SRT of 30 and 100 days, respectively. The high fraction of inert biomass predicted by the model was in accordance with the microscopic investigations of biomass viability in both reactors. The presented model was used to investigate the effect of increasing sludge age and the role of predators on the biomass composition of the tested SBR system.

Effluent standards for developing countries: combining the technology- and water quality-based approach.

It is a challenge for developing countries to realize socio-economical development without impairing water resources in an unacceptable way. A possible means for controlling water pollution is through defining, applying and enforcing effluent standards for wastewater discharges. However, in many developing countries the definition of effluent standards is still poor. They are either too stringent because they are based on standards from developed countries, or too relaxed and therefore they do not guarantee the safe intended uses of water. In order to define an approach for setting effluent standards that suits the needs and means of developing counties, water quality management practices in the USA, the EU, the New Independent States (NIS) and the Philippines were analyzed and compared. Four criteria (protection of the environment, technical viability, economic feasibility and institutional capacity requirements) were used to assess the suitability of these practices for developing countries. It is concluded that a combined approach that is based on best available technology not entailing excessive costs and environmental quality standards is the best way to define effluent standards that restrict water pollution against affordable costs.

Comparative performance studies of water lettuce, duckweed, and algal-based stabilization ponds using low-strength sewage.

A bench-scale continuous-flow wastewater treatment system comprising three parallel lines using duckweed (Spirodela polyrhiza), water lettuce (Pistia stratiotes), and algae (natural colonization) as treatment agents was set up to determine environmental conditions, fecal coliform profiles and general treatment performance. Each line consisted of four ponds connected in series fed by diluted sewage. Influent and effluent parameters measured included environmental conditions, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, nitrite, ammonia, total phosphorus, fecal coliforms, mosquito larvae, and sludge accumulations. Environmental conditions and fecal coliforms profiles were determined in the sediments (0.63 m), suspensions (0.35 m), and surfaces (0.1 m) of each pond. Acidic conditions were observed in the pistia ponds, neutral conditions in duckweed ponds, and alkaline conditions in algal ponds. Fecal coliforms log removals of 6, 4, and 3 were observed in algal, duckweed, and pistia ponds, respectively, in the final effluents, with die-off rates per pond of 2.7, 2.0, and 1.6. Sedimentation accounted for over 99% fecal coliform removal in most of the algal and pistia ponds. BOD removal was highest in the duckweed system, followed by pistia and algae at 95%, 93%, and 25%, respectively. COD removals were 65% and 59%, respectively, for duckweed and pistia, while COD increased in algal ponds by 56%. Nitrate removals were 72%, 70%, and 36%, respectively for duckweed, pistia, and algal ponds. Total phosphorus removals were 33% and 9% for pistia and duckweed systems, while an increase of 19% was observed in the algal treatment system. Ammonia removals were 95% in both pistia and duckweed and 93% in algal systems. Removals of total dissolved solids (TDS) were 70% for pistia, 15% for duckweed, and 9% for algae. Mosquito populations of 11,175/m(2), 3516/m(2), and 96/m(2) were counted in pistia, algal, and duckweed ponds, respectively. Low turbidity and low sludge accumulation characterized the macrophyte ponds. Performance in the removal of fecal coliforms in the algal-based treatment system and organic load removal in both macrophytes and algal-based treatment systems met the Ghana Environmental Protection Agency guideline values.

Improved method for determination of ammonia and nitrite oxidation activities in mixed bacterial cultures.

A simple and reliable method to measure the activity of ammonia and nitrite oxidisers in mixed bacterial cultures was developed. The developed method differentiates between the ammonia and nitrite oxidisers by consecutive injection of NO2- and NH4+. The main advantage of this method is that it avoids the use of metabolic inhibitors for ammonia or nitrite oxidisers, as used by other methods. Moreover, it allows measuring of the short-term effect of an inhibitor on both the ammonia and nitrite oxidisers in one test under controlled environmental conditions (pH, temperature). The developed method was applied to determine the inhibitory effects of salt (NaCl up to 15 g Cl/l) on an enriched culture of nitrifying bacteria. The results of the method demonstrate its potential to accurately determine the individual activities of nitrite and ammonia oxidisers.

Treatment of fish processing wastewater in a one- or two-step upflow anaerobic sludge blanket (UASB) reactor.

The performance of one-step UASB reactors treating fish processing wastewater of different lipid levels was determined using artificially generated influent simulating that of the canning of sardines and tuna. The organic loading rates (OLR) and the hydraulic retention times (HRT) were 5-8 g COD.l(-1).d(-1) and 11-12 hours, respectively. In treating a wastewater that contains 3-4 g.l(-1) total COD of which 5-9% was lipids, the COD removal and conversion to methane were ca.78% and 61%, respectively. In treating a wastewater with a higher lipid content (ca. 47% of the total COD), the total COD removed and converted to methane were 92% and 47%, respectively. A considerable part of the influent total COD was removed via adsorption on reactor surfaces and sludge particles. The adsorption of lipids on sludge particles threatens the stability of the UASB operation. Thus, the performance of a first-step UASB reactor in removing suspended solids (SS) from a "high-lipid" wastewater was also determined in this study.

The effect of pH on enterococci removal in Pistia-, duckweed- and algae-based stabilization ponds for domestic wastewater treatment.

A batch scale experiment was conducted to determine the effect of pH on enterococci die-off. A continuous flow system was also established to determine the environmental conditions and their effects on enterococci removal. The batch experiment was conducted for pHs: 4, 5, 7, 9, and 11 under light and dark conditions. Enterococci and DO were measured every day and every other day respectively for nine days. Pathogen removal rates at pH 4, 5, 7, 9 and 11 in the light/dark were (expressed as d(-1)) -2.1/-2.1, -2.1/-1.5, -2.1/-1.5, -2.1/-1.4 and -1.1/-1.0, respectively. DO levels were low, between 0.17 mg/L at pH 4 (light) to 0.56 mg/L at pH 7 (light). The continuous flow system consisted of Pistia (water lettuce), duckweed and algal treatments in series of four ponds with a total retention period of 28 days after two days of anaerobic pre-treatment. After two months of operation, temperature, pH, DO, TDS, and enterococci populations were monitored. A low pH of 4.4 was obtained in the Pistia ponds. Neutral conditions were observed in the duckweed system, while pH values >9 were observed in the algal system. Enterococci decreased from 7.8 x 10(6) to <500/100 ml in all treatment systems after 28 days of treatment with no significant differences between treatments.

Rhizosphere Acidification by Iron Deficient Bean Plants: The Role of Trace Amounts of Divalent Metal Ions: A Study on Roots of Intact Plants with the Use of C- and P-NMR.

Rhizosphere acidification by Fe-deficient bean (Phaseolus vulgaris L.) plants was induced by trace amounts of divalent metal ions (Zn, Mn). The induction of this Fe-efficiency reaction was studied by (14)CO(2) and (11)CO(2) fixation experiments, and with (31)P-NMR on roots of whole plants. The starting and ending of an acidification cycle was closely coupled to parallel changes in CO(2) fixation, within the maximal resolution capacity of 20 min. (31)P-NMR experiments on intact root systems showed one peak which was ascribed to vacuolar free phosphate. At the onset of proton extrusion this peak shifted, indicating increase of pH in the cells. Proton extrusion was inhibited, with a lag period of 2 hours, by the protein synthesis inhibitors cycloheximide and hygromycin. It is assumed that Zn and Mn induce proton extrusion in Fe-deficient bean roots by activating the synthesis of a short-living polypeptide; the NMR data suggest a role for this peptide in the functioning of a proton pumping ATPase in the plasma membrane.

Rhizosphere acidification as a response to iron deficiency in bean plants.

Iron deficiency in higher plants causes accumulation of salts of organic acids in the roots, the most characteristic being citrate. We show that citrate and malate accumulate in beans (Phaseolus vulgaris L. var Prélude), not because of a lack of the iron-containing enzyme aconitase (EC 4.2.1.3), but in close coupling to the extrusion of protons during rhizosphere acidification, one of the ;Fe-efficiency' reactions of dicotyledonous plants. When proton excretion is induced in roots of control bean plants by addition of fusicoccin, only malate, not citrate, is accumulated. We propose that iron deficiency induces production of organic acids in the roots, which in beans leads to both proton excretion and an increased capacity to reduce ferric chelates via the induced electron transfer system in the root epidermis cells.

Photosynthetic electron transfer and membrane energization in spheroplasts and membrane vesicles of the thermophilic cyanobacterium Synechoccus 6716.

The higher the incubation temperature, the higher the light intensity that membrane vesicles of the thermophilic cyanobacterium Synechococcus 6716 require for the saturation of O2-production. If membrane vesicles are incubated at temperatures at which intact cells are growing optimally, photosynthetic O2-production and membrane energization decrease rapidly, suggesting that the thermophilic properties are rapidly lost. If membrane integrity is maintained (spheroplasts) the harmful effect of higher temperatures is much less. The effects of 2,5-dibromo-3-methyl-6-isopropyl-p-benzo-quinone (DBMIB), 5-chloro-3-t-butyl-2'-chloro-4'-nitrosalicylanilide (S-13), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and N,N'-dicyclohexylcarbodiimide (DCCD) are the same as in chloroplasts, be it that DCCD acts as an electron transfer inhibitor at higher concentrations. The supposed alternative site of DCMU inhibition in cyanobacteria is rejected.Spheroplasts show a reversible energy-dependent fluorescence quenching of 9-amino-6-chloro-2-methoxyacridine (ACMA) caused by illumination. ATP hydrolysis only give rise to fluorescence quenching in membrane vesicles. Long incubation at higher temperatures reduces the fluorescence quenching of membrane vesicles and spheroplasts, the latter being more stable than the former.

Characterization of reconstituted ATPase complex proteoliposomes prepared from the thermophilic cyanobacterium Synechococcus 6716.

The preparation and some properties are described of proteoliposomes consisting of the ATPase complex and lipids from the thermophilic cyanobacterium Synechococcus 6716. In the proteoliposomes (about 200 nm in diameter) only a low amount of protein can be incorporated (protein/lipid ratio of 0.01 w/w) and they show very few protein particles on freeze-fracture replicas. The octyl glucoside and cholate dialysis method of reconstitution yielded stable proteoliposomes with a relatively low proton permeability. ATP hydrolysis and 32Pi/ATP exchange activities were about 400 and 120 nmol X min-1 X mg protein-1, respectively; the former was strongly stimulated by an uncoupler. ATP hydrolysis induces membrane energization as monitored by membrane-potential- and surface-potential-indicating probes and by different pH indicators trapped inside the vesicles. The probes used were a membrane-bound fluorescent aminoacridine, which monitors surface charge-density changes, the native carotenoids and added oxonol VI for monitoring electrical potential in the membrane and the pH indicators neutral red and cresol red. The different rise kinetics of these probes indicate that proton accumulation upon ATP hydrolysis involves at least two steps: a membrane-localized potential charge and proton transfer followed by a much slower acidification of the bulk intravesicular space. Internal neutral red and cresol red seem to discriminate between proton translocation to the internal interface and bulk space, respectively.

Isolation, purification and characterization of the ATPase complex from the thermophilic cyanobacterium Synechococcus 6716.

The ATPase complex is isolated and purified from membrane vesicles of the thermophilic cyanobacterium Synechococcus 6716 by octyl glucoside and cholic acid by a modification of the procedure for its extraction from spinach chloroplasts. The complex is purified by differential centrifugation and ammonium sulfate precipitation and by gel filtration on Sepharose 6B. The purified fraction, without any phycocyanin contamination, shows ATP hydrolysis activity and Pi/ATP exchange activity of 1564 and 350 nmol X min-1 X mg protein-1, respectively. N,N'-Dicyclohexylcarbodiimide inhibits the ATP hydrolysis activity of this purified fraction. On polyacrylamide gels most typical F1 ATPase polypeptides are identified, but the low-molecular weight polypeptides visible cannot be ascribed to the F0 part of the complex with certainty; non-identified bands around 30 kDa are also present.