Biological Treatment of Landfill Leachate Using Sea Water Microflora Under Aerobic and Anaerobic Conditions

The present study demonstrates an appropriate technique for treatment of landfill leachate. Pretreatment with alum and anionic poly electrolyte as coagulant and flocculent materials caused 43% reduction of COD. Sucrose and nutrient broth were used for enrichment of sea water microflora. The pretreated leachate was used for determination of aerobic and anaerobic biological treatments of sea water enriched microflora. BOD5, COD and TSS reduction were acquired in best samples 90.3%, 95.1% and 44.8% in aerobic and 31.2%, 38.3% and 37.3% in anaerobic conditions, respectively. The metal removal was determined in aerobic and anaerobic treatments and up to 90% metal removal acquired in some cases.


Introduction
Leachate is one of the main environ mental concerns associated with landfill management because it contains pollutions such as organic matter, heavy metals, and salts which have the potential to damage the quality environ ment and are the real damage after co mposting [1]. Leachate co mp os it ion is un reliab le and s pace at a part icu lar landfill [2]. The composition of the leached waste water is based on the composition and the degree of contouring and compacting of co mpost, climates conditions at the landfill, local rainfall that regulates humidity level, temperature and landfill age. These conditions must be fixed and treated ap p ro p riat ely , t o av o id con t amin at ion o f receiv ing environment [3]. Treat ment methods must be coordinated to the actual ind iv iduality of the exacting leachate [4]. To remove the majority of pollutants, biological methods used beside with physicochemical treat ment [15]. Usually, only application of biological treat ment is not an option due to t he leach at e d is t in ct iv en ess [1]. In ad d it io n , neith er biological nor physicochemical treat ment alone ach ieves high treat ment efficiencies sign ificant for occurrence of high-mo lecular weight organics that are difficult to remove and inhibitory effects of organics, inorganic salts and metals for waste microorgan is ms [1]. A mong various biolog ical technologies, it is smart to use mutual anaerobic and aerobic systems for the removal of COD and ammonia, especially for the treatment of landfill leachate [5]. In pred ictable biological reactor, ano xic, anaerobic and aerobic conditions are separated in sequencing sets of reactors [6]. Up to now many b iological treat ments like, up-flo w anaerobic; sludge blanket reactor [7,8]; anaerobic sequencing batch reactor [8]; aerated lagoons and activated sludge [9] have been investigated for Leachate treatment. The kind of treatment should be based on characteristics of leachate.
Conductivity is used as an indicator of the abundance of dissolved inorganic species, chemicals or total concentration of ions like sodium, potassium and chloride in water. Conductivity is not a p roblem in itself and just because it is above certain level does not mean that the water will cause infection [16,10].However h igh salt in the leachate make it resistant to biodegradation.
In this research biological treat ment of leachate by marine microorganism was investigated for first time. A lso the objective was to evaluate the biological treatability of the leachate from municipal landfill sites by observing removal capacity of COD and organic pollutants. The heavy metals removals were also investigated.

Sampling of Landfill Leachate
Ten liters of leachate was directly taken fro m a 21-yr old landfill located in Gardane Zeinal in Isfahan-Iran. Leachate is collected by drainage pipes into the commercially and sandy lagoons, whereas no treatment process are performed.
The analysis of this leachate was carried out and the results are given in Table 1. The leachate was stored at -40℃ in the refrigerator to keep the composition as uniform as possible for future experiments.

Coagulation and Flocculation
Coagulation-flocculation experiments with jar test equipment, equipped with four beakers with different coagulants Al 2 (SO 4 ) 3 , FeCl 3 , FeSO 3 and an ionic polyelectrolyte as flocculants (supplied fro m Merck) at various dosages on removing the COD of leachate were investigated. First, pH of samples were read justed to desired pH 6.5 (Metroh m 632) by addition of 1N NaOH and then the varying coagulant concentrations at roo m temperature (20℃ ) were added into 1 L of the raw landfill leachate. The samples were treated by fast mixing for 3 minute (120 rp m), slow mixing fo r 15 min (20rp m) and 1 hour's sedimentation with chemical coagulation, the final gravity settling stage lasted for another 24-48 h, and then the supernatant was analyzed for COD according to Standard Methods [17].

Biodegradability Testing
Biodegradability of the raw landfill leachate was determined by applying, enriched microorganis ms fro m (high salt environments) sea water. We determined the biodegradability of the leachate by sea microflo ra, and to avoid any toxic material, p retreated leachate was used. The experiment included enrich ment, incubation and investigation of treatment e fficiency. The main items pH, BOD 5 (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), EC (electrical conductivity) were monitored using the standard methods recommended by US Environmental Protection Agency [17].

En rich ment of Sea Water Microflora
Different substances such as, sucrose (10 g l-1), nutrient broth (1gr per 100cc sea water), cellulose with yeast extract (0.5 grl-1 and 2 grl-1 respectively) were used for enrich ment of sea water flora indiv idually. En rich ment was performed in aerobic and anaerobic condition. Aerobic med iu ms were placed on 37℃ shaker incubator at 200rp m for one week. Closed tap bottles were choose for anaerobic condition and mediu ms incubated 3 week at 37℃ incubator. The suspensions were centrifuged after enrich ment and the pellets were used as biomass.

Characterization of the Landfill Leachate
The characterization of raw leachate fro m Isfahan landfill is shown in table 1. It contains high concentrations of organic and inorganic material, thus released leachate may cause serious pollution to ground water aquifers as well as adjacent surface waters. the acidic pH might caused by plenty of volatile fatty acids like acet ic acids, lactic acids and amino acids that exist in foods and fruits and also, the high partial pressure of CO 2 . High salt concentrations in the leachate are due to the great amount of foods waste, disposed in to the landfill. The main reasons for the presence of Na in the leachate are the wide use of Na salts in industry and domestic activity (paper, soap, etc) [18]. Potassium is released during refuse decomposition and the main source of K is plant material and discarded food, which is the main co mponent of Iranian municipal solid waste. The presence of heavy metals in the leachate is due to industrial waste and household nonhazardous waste [19]. Heavy metals if not removed, could cause serious consequences to human beings and the environment. Heavy metals can accumulate in the biological tissues of the body and cause serious diseases such as neurotoxin effects, renal failure (lead), genetic anomalies and cancer risk (cadmiu m, arsenic). Th is indicates clearly that need for pretreat ment of leachate prior to bio logical treat ment [11].

Coagul ati on and Fl occulation
The composition of the leached wastewater is based on the composition and the degree of contouring and compacting of solid wastes, physicochemical conditions at the landfill, local rainfall reg ime that regulates moisture level, geology and landfill age [3]. According to Tab le 1, we conclude that old leachate with a BOD5/ COD ratio of 0.36 could be considered as relat ively stabilized wastewater. Thus, using biological processes for further t reat ment of these wastes may be ineffect ive and other methods such as chemical coagulation could be applied. Although the coagulation/flocculation is relat ively a simp le technique, this treatment only allows to moderate removal of organic compounds. A few negative situations such as sludge generation and high aluminu m concentration were revealed after this process.
The leachate sample in this study was coagulated by different coagulant with anionic polyelectrolyte (Table 2). It should be noted that precipitation of alu m by organic compounds in leachate is more than other coagulants. Treat ment efficiency (Fig.1) according to COD, reached 43% at 1500mg.l−1 of A l 2 (SO 4 ) 3 and anionic polyelectrolyte. Many reports related to chemical treat ment of leachate are availab le. In an old landfill leachate by an initial COD of 2461mg .l-1, reported that COD was removed 25% with 1000mg.l-1 alu m [12]. It was recognize that, low amount of flocculent (2.5 mg.l-1) have better treatment efficiency in removal o f COD (51%) than higher amounts.

Biological Treatment by the Sea Microflora In Aerobic and Anaerobic Conditions
During acco mplished investigations in this project, sea micro flora was used because of high concentration of salt and organic load of Isfahan landfill. Microorganisms are not able to grow well on this wastewater and biological treatment does not work perfectly. Whereas chemical qualities of leachate, such as Electrical Conductivity and concentration of h igh salt, is similar with chemical qualities of the sea water, it was recognizab le that sea microflo ra could tolerate this special landfill wastewater and could reduced organic compounds. Therefore for the first time in this project, we used enriched sea water microflora. It was enriched in three materials, and after inoculation in the leachate, experiments accomplished. Figure 2 shows the BOD and COD reduction efficiency in aerobic system. With the degradation of organics by enriched microflora in nutrient broth and sucrose, the BOD reduction in the system increased at the early stage, and reached maximu m value of 90.3% on day 7, then remained stable. Whereas cellulose enriched microflora doesn't represent enough effect on reduction of BOD and COD. Also the best reduction of TSS was showed in samples with addition of nutrient broth and sucrose (43.2 and 44.8% respectively).
The table 3 shows BOD, COD and TSS reduction of leachate after treat ment with different enriched microflo ra in anaerobic conditions within 21 days.
The table 4 and 5 shows removal efficiency of metals in the treated leachate with nutrient broth and sucrose in aerobic and anaerobic conditions. There are significant effects on Fe, Cu, and Mg removal.
Melgie et.al (2010) for extract ing heavy metals used 2 samples of sea water and Karoon's Lake water, and isolated 13 microorganisms (bacteria and fungi). they reported that fungal have superior potential in adsorbing of heavy metals, so that A.niger and A.flavus absorbed about 97.88% o f the sodium ions in the sea water wh ile bacterial absorbed about 54.84 % wh ich reflected the absolute requirement of these organisms to sodium ions . Both bacterial and fungous absorbed High amounts of Mg ions. It shows that Mg +2 ions play an important ro le in many key metabolic reactions catalyzed by enzymes. Co mbination of bacterial isolates absorbed 90.13 % of the dissolved K + ions in sea water, while fungal isolates absorbed lower quantities of K + ions. Co mbination of bacterial and fungal isolates (A.niger, A.flavus, M.roseus, M.kristinae and V.fluvials) is capable to absorb different metal ions as lead, copper, iron, cad miu m and zinc in/on their cells [13].
Sabry et.al in 1996 studied the resistance patterns by a community of marine, aerobic heterotrophic and metal-resistant bacteria. The resistance patterns, exp ressed that, a great part of the isolates were sensitive to cadmiu m (99%), zinc (84%), nickel (40%) and copper (22%) [14].
Removal efficiency of anaerobic treatments on the leachate is shown in table 5.

Conclusions
An innovative method was demonstrated to treat landfill leachate. In order to evaluate the biological treatability of the landfill leachate, the removal efficiency of COD, BOD and organic pollutants were investigated. Landfill leachate generated from Isfahan landfill site was of very poor quality, with high concentrations of numerous organic pollutants. The COD concentration was between 176000 and 127000 mg L -1 . The BOD concentration was between 49000 and 37000 mg L -1 . The COD and BOD removal efficiency was about 93% and 92%, respectively after treat ment in the bio-reactor. The average effluent concentrations of COD and BOD were aboute 15000 and 5000 mg L -1 , respectively.