Andrzej Białowiec

Nitrogen removal from landfill leachate in constructed wetlands with reed and willow: Redox potential in the root zone

This study investigated the effects of reed and willow on bioremediation of landfill leachate in comparison with an unplanted control by measuring redox potential levels in the rhizosphere of microcosm systems in a greenhouse. Plants had a significant influence on redox potential relative to the plant-less system. Redox potential in the reed rhizosphere was anoxic (mean -102±85 mV), but it was the least negative, being significantly higher than in the willow (mean -286±118 mV), which had the lowest Eh. Redox potential fluctuated significantly in the willow rhizosphere during daylight hours, with large decreases in the morning. Levels of NH(4)(+) decreased significantly in the first day of the experiment and remained at similar low levels in all three variants for the next four weeks of the experiment. Following this removal of ammonia significant peaks in NO(2)(-) occurred in the control and reed tanks on the 1st day, and again on 14th day in the control tank up to 13 mg/dm(3). In the willow tank there was also one significant peak of NO(2)(-) in the first week, but only up to 0.5 mg/dm(3). Significant accumulation, within 21 days of NO(3)(-) in all variants was observed, but in tanks with reed and willow the concentration of NO(3)(-) remained significantly lower (<4 mg/dm(3)) than in the unplanted tank (∼35 mg/dm(3)). Final levels of total-nitrogen, nitrate and chemical oxygen demand were considerably lower in the reed and willow tank than in the unplanted tank.

Effectiveness of leachate disposal by the young willow sprouts Salix amygdalina

The lysimeter experiment was conducted at the laboratory scale. Different water and leachate dilutions (0%, 25%, 50%, 100% of leachate) were supplied to the lysimeters to achieve the variation in pollutants concentration. The measure of leachate disposal effectiveness was the amount of evaporated leachate solution in evapotranspiration and transpiration. Analysis of evaporation dynamics and the impact of the plants on the leachate disposal effectiveness were determined. Correlation between biomass increase, transpiration and leachate concentration was observed. The highest evapotranspiration was obtained in the lysimeter with leachate concentration 25% and was on the level of 2.3 mm/day and for transpiration, 2.21 mm/day. The lowest values of evapotranspiration (0.55 mm/day) and transpiration (0.39 mm/day) were observed in the lysimeters supplied only by concentrated leachate. The highest leachate treatment efficiency 0.78 mm leachate/day was achieved in lysimeter K3-50% leachate concentration. There was an increase in transpiration participation in evapotranspiration in time. In the lysimeters supplied by the solutions with leachate concentrations, 25% and 50% transpiration participation in evapotranspiration ranged from 80% to 90%, in case of concentrated leachate from 60% to 70%. Evapotranspiration in all lysimeters was 3, 5-14 times higher than evaporation. It seems to be the result of plant impact on evaporation and confirms the possibility of this method being used for leachate treatment. Willows in lysimeter (K3-50% of leachate) had the most effective physiological fit to landfill leachate treatment.

Using fractal geometry to determine phytotoxicity of landfill leachate on willow

Phytotoxicological tests were conducted during 6weeks on the willow Salix amygdalina using six concentrations of landfill leachate. Plants were exposed to landfill leachate solutions using two regimes: (A) - the willow shoots were watered by leachate solution from the beginning of the test; (B) - the willow shoots were cultivated in pots with clean water during 4weeks, then water was exchanged for leachate solutions. The tolerance of plants to prepared leachate concentration was determined by observations of morphological parameters of leaves including their fractal dimension. The lowest effective concentration (LOEC) was calculated. Results showed that in regime A, all measured parameters indicated similar response of plants to phytotoxic compounds in leachate. The LOEC was in the range 4.69-5.63% of leachate concentration. In regime B, only such parameters as leaf length and fractal dimension indicated a marked response (LOEC was much lower for other parameters, 0.8% and 1.84% respectively). Leaf length and, especially, fractal dimension are shown to be good indicators of plant response to toxicants in their environment.

Phytotoxicity of landfill leachate on willow - Salix amygdalina L.

Because of low investment and operational costs, interest is increasing in the use of willow plants in landfill leachate disposal. Toxic effects of leachate on the plants should be avoided in the initial period of growth and phytotoxicological testing may be helpful to select appropriate leachate dose rates. The aim of this study was to determine the phytotoxicity of landfill leachate on young willow (Salix amygdalina L.) cuttings, as a criterion for dose rate selection in the early phase of growth. Over a test period of 6 weeks plants were exposed to six concentrations of landfill leachate solutions (0%; 6.25%; 12.5%; 25%; 50% and 100%), under two different regimes. In regime A willow plants were cultivated in leachate solution from the beginning, whereas in regime B they were grown initially in clean water for 4 weeks, after which the water was exchanged for leachate solutions. The lowest effective concentration causing toxic effects (LOEC) was calculated (p<0.05). In regime A LOEC was between 5.44% and 6.50% of leachate concentration, but slightly higher in regime B (5.32-6.59%). Willow plants were able to survive in landfill leachate solutions with electrical conductivity (EC) values up to 5.0 mS/cm in regime A, whereas in regime B plants were killed when EC exceeded 3.0 mS/cm. This indicates an ability of willow plants to tolerate higher strengths of landfill leachate if they are cultivated in such concentrations from the beginning.

The controlling of landfill leachate evapotranspiration from soil-plant systems with willow : Salix amygdalina L

The use of willows (Salix amygdalina L) to manage landfill leachate disposal is an effective and cost-effective method due to the high transpiration ability of the willow plants. A 2-year lysimetric experiment was performed to determine an optimum leachate hydraulic loading rate to achieve high evapotranspiration but exert no harmful influence on the plants. The evapotranspiration rate of a soil–plant system planted with the willow was 1.28–5.12-fold higher than the rate measured on a soil surface lacking vegetation, suggesting that soil– willow systems with high volatilization rates are a viable landfill leachate treatment method. Of the soil–willow systems, the one with willow growing on sand amended with sewage sludge soil at an hydraulic loading rate of 1 mm day-1 performed best, with evapotranspiration ranging from 2.25 to 3.02 mm day-1 and a biomass yield of 8.0–9.85 Mg dry matter ha-1. The organic fraction of the soil increased as much as 2.5% of dry matter, due to the sewage sludge input, which exerted a positive effect on the biomass yield as well as on transpiration and evaporation. It was observed that the plants in the sand-and-sewage sludge soil systems displayed higher resistance to toxic effects from the applied landfill leachate relative to plants in the sand–soil systems.

The pyrolysis and gasification of digestate from agricultural biogas plant

Abstract Anaerobic digestion residue represents a nutrient rich resource which, if applied back on land, can reduce the use of mineral fertilizers and improve soil fertility. However, dewatering and further thermal processing of digestate may be recommended in certain situations. Limited applicability of digestate as fertilizer may appear, especially in winter, during the vegetation period or in areas where advanced eutrophication of arable land and water bodies is developing. The use of digestate may be also governed by different laws depending on whether it is treated as fertilizer, sewage sludge or waste. The aim of this paper is to present the effects of thermal treatment of solid fraction of digestate by drying followed by pyrolysis and gasification. Pyrolysis was carried out at the temperature of about 500°C. During this process the composition of flammable gases was checked and their calorific value was assessed. Then, a comparative analysis of energy parameters of the digestate and the carbonizate was performed. Gasification of digestate was carried out at the temperature of about 850°C with use of CO2 as the gasifi cation agent. Gasification produced gas with higher calorific value than pyrolysis, but carbonizate from pyrolysis had good properties to be used as a solid fuel Streszczenie Pozostałości z biogazowni rolniczych stanowią bogaty w substancje nawozowe surowiec, w przypadku którego, jego rolnicze wykorzystanie, może zmniejszyć stosowanie nawozów mineralnych i poprawić właściwości gleby. Jednakże poferment powinien być wcześniej odwodniony i przetworzony termicznie. Ograniczona stosowalność w środowisku przyrodniczym pofermentu może szczególnie wystąpić w okresie zimowym oraz na terenach zagrożonych eutrofi zacją. Wykorzystanie pofermentu podlega także ograniczeniom prawnym w zależności od tego czy jest traktowany jako nawóz, osad lub odpad. Celem artykułu jest przedstawienie efektów zastosowania termicznego przetwarzania odwodnionego pofermentu w procesach pirolizy i zgazowania. Proces pirolizy pofermentu prowadzono w temperaturze 500°C. Monitorowano skład i kaloryczność gazu pirolitycznego. Wykonano porównawcze analizy kaloryczności odwodnionego pofermentu i uzyskanego w wyniku pirolizy karbonizatu. Gazyfi kację prowadzono w temperaturze 850°C w atmosferze CO2. Wykazano, iż uzyskany w procesie gazyfi kacji gaz syntezowy posiadał wyższą kaloryczność, jednak dodatkowy produkt procesu pirolizy karbonizat posiadał dobre właściwości do wykorzystania jako paliwo stałe.

Recycling potential of air pollution control residue from sewage sludge thermal treatment as artificial lightweight aggregates

Thermal treatment of sewage sludge produces fly ash, also known as the air pollution control residue (APCR), which may be recycled as a component of artificial lightweight aggregates (ALWA). Properties of APCR are typical: high content of Ca, Mg, P2O5, as well as potential to induce alkaline reactions. These properties indicate that ALWA prepared with a high content of APCR may remove heavy metals, phosphorus, and ammonium nitrogen from wastewater with high efficiency. The aim of this preliminary study was to determine the optimal composition of ALWA for potential use as a filter media in wastewater treatment systems. Five kinds of ALWA were produced, with different proportions of ash (shown as percentages in subscripts) in mixture with bentonite: ALWA0 (reference), ALWA12.5, ALWA25, ALWA50, and ALWA100. The following parameters of ALWA were determined: density, bulk density, compressive strength, hydraulic conductivity, and removal efficiency of ions Zn2+, NH4+, and PO43−. Tests showed that ALWA had good mechanical and hydraulic properties, and might be used in wastewater filtering systems. Phosphates and zinc ions were removed with high efficiency (80-96%) by ALWA25-100 in static (batch) conditions. The efficiency of ammonium nitrogen removal was low, <18%. Artificial wastewater treatment performance in dynamic conditions (through-flow), showed increasing removal efficiency of Zn2+, PO43− with a decrease in flow rate.

Is the biochar produced from sewage sludge a good quality solid fuel

Abstract The influence of sewage sludge torrefaction temperature on fuel properties was investigated. Non-lignocellulosic waste thermal treatment experiment was conducted within 1 h residence time, under the following temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as lignocellulosic reference material. The following parameters of biochar have been measured: moisture, higher heating value, ash content, volatile compounds and sulfur content. Sawdust biochar has been confirmed to be a good quality solid fuel. High ash and sulfur content may be an obstacle for biochar energy reuse. The best temperature profile for sawdust torrefaction and fuel production for 1 h residence time was 220°C. At this temperature the product contained 84% of initial energy while decreased the mass by 25%. The best temperature profile for sewage sludge was 240°C. The energy residue was 91% and the mass residue was 85%. Higher temperatures in both cases caused excessive mass and energy losses.

The RDF/SRF torrefaction: An effect of temperature on characterization of the product – Carbonized Refuse Derived Fuel

The influence of Refuse Derived Fuel (RDF)/Solid Recovery Fuel (SRF) torrefaction temperature on product characteristic was investigated. RDF/SRF thermal treatment experiment was conducted with 1-h residence time, under given temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as reference material. The following parameters of torrefaction char from sawdust and Carbonized Refuse Derived Fuel (CRDF) from RDF/SRF were measured: moisture, calorific value, ash content, volatile compounds and sulfur content. Sawdust biochar was confirmed as a good quality solid fuel, due to significant fuel property increase. The study also indicated that RDF torrefaction reduced moisture significantly from 22.9% to 1.4% and therefore increased lower heating value (LHV) from 19.6 to 25.3MJ/kg. Results suggest that RDF torrefaction may be a good method for increasing attractiveness of RDF as an energy source, and it could help unify RDF properties on the market.

Transpiration as landfill leachate phytotoxicity indicator.

An important aspect of constructed wetlands design for landfill leachate treatment is the assessment of landfill leachate phytotoxicity. Intravital methods of plants response observation are required both for lab scale toxicity testing and field examination of plants state. The study examined the toxic influence of two types of landfill leachate from landfill in Zakurzewo (L1) and landfill in Wola Pawłowska (L2) on five plant species: reed Phragmites australis (Cav.) Trin. ex Steud, manna grass Glyceria maxima (Hartm.) Holmb., bulrush Schoenoplectus lacustris (L.) Palla, sweet flag Acorus calamus L., and miscanthus Miscanthus floridulus (Labill) Warb. Transpiration measurement was used as indicator of plants response. The lowest effective concentration causing the toxic effect (LOEC) for each leachate type and plant species was estimated. Plants with the highest resistance to toxic factors found in landfill leachate were: sweet flag, bulrush, and reed. The LOEC values for these plants were, respectively, 17%, 16%, 9% in case of leachate L1 and 21%, 18%, 14% in case of L2. Leachate L1 was more toxic than L2 due to a higher pH value under similar ammonia nitrogen content, i.e. pH 8.74 vs. pH 8.00.