Biological treatment of shrimp production wastewater

Over the last few decades, there has been an increase in consumer demand for shrimp, which has resulted in its worldwide aquaculture production. In the United States, the stringent enforcement of environmental regulations encourages shrimp farmers to develop new technologies, such as recirculating raceway systems. This is a zero-water exchange system capable of producing high-density shrimp yields. The system also produces wastewater characterized by high levels of ammonia, nitrate, nitrite, and organic carbon, which make waste management costs prohibitive. Shrimp farmers have a great need for a waste management method that is effective and economical. One such method is the sequencing batch reactor (SBR). A SBR is a variation of the activated sludge biological treatment process. This process uses multiple steps in the same reactor to take the place of multiple reactors in a conventional treatment system. The SBR accomplishes equalization, aeration, and clarification in a timed sequence in a single reactor system. This is achieved through reactor operation in sequences, which includes fill, react, settle, decant, and idle. A laboratory scale SBR was successfully operated using shrimp aquaculture wastewater. The wastewater contained high concentrations of carbon and nitrogen. By operating the reactors sequentially, namely, aerobic and anoxic modes, nitrification and denitrification were achieved as well as removal of carbon. Ammonia in the waste was nitrified within 4 days. The denitrification of nitrate was achieved by the anoxic process, and 100% removal of nitrate was observed within 15 days of reactor operation.     

Biological treatment specific for an industrial wastewater containing s-triazines

Mixed cultures of bacteria grew in medium containing real s-triazine wastes as nitrogen source. About 80% of the s-triazine waste could be degraded as determined by HPLC and by measurements of dissolved nitrogen. The culture required an added carbon source in order to degrade s-triazines. A temperature optimum near 40 degrees C was observed and a salt concentration above about 4% markedly retarded growth and the degradation of s-triazines. This system was examined as a biological treatment for wastes from syntheses of s-triazines.     

Biological treatment of olive mill wastewater by non-conventional yeasts

The ability of lipolytic yeasts to grow on olive mill wastewater (OMW)-based medium and to produce high-value compounds while degrading this waste, was tested. OMW collected from three-phase olive mills from the North region of Portugal were characterized and used. OMW with COD ranging from 100 g L⁻¹ to 200 g L⁻¹ were supplemented with yeast extract and ammonium chloride. Studies of OMW consumption were carried out in batch cultures of Candida rugosa, Candida cylindracea and Yarrowia lipolytica. All strains were able to grow in the OMW-based media, without dilution, to consume reducing sugars and to reduce COD. C. cylindracea was the best strain concerning the lipase production and the reduction of phenolic compounds and COD. For all strains, the phenols degradation was quite difficult, mostly when more easily degradable carbon source is still present in the medium. Among the phenolic compounds tested catechol is the most inhibitory to the cells.     

Biological treatment of high strength wastewater by fed-batch operation

Biological treatment systems for high strength wastewaters are usually operated in continuous mode such as activated sludge systems. When operated at steady-state, continuous systems result in constant effluent standards. However, in the presence of shock loadings and/or toxic compounds in feed wastewater, system performance drops quite significantly as a result of partial loss of microbial activity. In fed-batch operation, wastewater is fed to the aeration tank with a flow rate determined by effluent standards. In this type of operation, wastewater can be fed to biological oxidation unit intermittently or continuously with a low flow rate without any effluent removal. Feed flow rate is adjusted by measuring COD concentration in the effluent. As a result of intermittent addition of wastewater high COD concentrations and toxic compounds are diluted in large volume of aeration tank and inhibition effects of those compounds are reduced. As a result, biological oxidation of these compounds take place at a much higher rate. In order to show the aforementioned advantage of fed-batch operation, a high strength synthetic wastewater consisting of diluted molasses, urea, KH₂PO₄ and MgSO₄ was treated in an biological aeration tank by fed-batch operation. Organisms used were an active and dominant culture of Zooglea ramigera commonly encountered in activated sludge operations. COD removal kinetics was found to be first order and the rate constant was determined.     

Biocoenosis and degradation in model wastewater treatment plants

Summary The bacteria and protozoa of laboratory models for wastewater treatment plants have been determined and compared to species from ordinary plants. A determination key specially designed for the bacteria of wastewater treatment plants has been developed. Large changes in the composition of the bacterial populations were found in the model open laboratory plant system. Tests with a model sterile closed plant and reproducible inoculum have been performed to get a constant bacteria population to improve the comparability and reproducibility for substance degradation test.     

Biological treatment of tannery wastewater by using salt-tolerant bacterial strains

Background  

High salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater.     

Biological treatment and toxicity of low concentrations of oily wastewater (bilgewater)

The biodegradability and toxicity of low concentrations of oily wastewater (bilgewater) were tested under simulated sanitary wastewater treatment conditions. This was done to establish the feasibility of a combined shipboard oily and nonoily wastewater treatment system. The biodegradability of oily wastewater was determined by proxy; 14C-labeled dodecane, toluene, and phenanthrene (representing alkane, aromatic, and polyaromatic compounds, respectively) were mineralized in petroleum fuels and lubricants. We found that low concentrations of oily wastewater components were mineralized, even in the presence of more abundant substrates (such as synthetic graywater, containing vegetable oil, detergent, gelatin, and starch). The toxic effects of diesel fuel and several other components of oily wastewater (such as surfactants and a synthetic lubricant) on a na?ve wastewater assemblage was also tested. In concentrations much higher than would be expected under normal shipboard conditions, we found no evidence of toxic effects of the bilgewater compounds tested. Thus, a combined shipboard bilgewater and sanitary wastewater system might be feasible.     

Biological coupling process for treatment of toxic and refractory compounds in coal gasification wastewater

Coal gasification wastewater (CGW) contains a large number of toxic and refractory compounds, such as phenolic compounds and polycyclic and heterocyclic aromatic compounds. These toxic and refractory compounds are difficult to degrade if biological methods are the only ones used. In recent years, several novel biological coupling processes are used to treat CGW. In the study, this review attempts to offer a comprehensive summary regarding the biological coupling treatment technologies of CGW, including conventional biological processing arts, the combination of adsorption and biotechnology, biological enhancement technologies, co-metabolism technologies and the combination of advanced oxidation and biotechnology. Meanwhile, the treatment efficiency of different biological coupling processes was compared with each other. Co-metabolism and advanced oxidation with biotechnology are both highly effective and promising technologies for degrading toxic and refractory compounds. More research should be conducted on these two aspects in the future.     

Synapse fits neuron: joint reduction by model inversion

In this paper, we introduce a novel simplification method for dealing with physical systems that can be thought to consist of two subsystems connected in series, such as a neuron and a synapse. The aim of our method is to help find a simple, yet convincing model of the full cascade-connected system, assuming that a satisfactory model of one of the subsystems, e.g., the neuron, is already given. Our method allows us to validate a candidate model of the full cascade against data at a finer scale. In our main example, we apply our method to part of the squid’s giant fiber system. We first postulate a simple, hypothetical model of cell-to-cell signaling based on the squid’s escape response. Then, given a FitzHugh-type neuron model, we derive the verifiable model of the squid giant synapse that this hypothesis implies. We show that the derived synapse model accurately reproduces synaptic recordings, hence lending support to the postulated, simple model of cell-to-cell signaling, which thus, in turn, can be used as a basic building block for network models.     

Biological wastewater treatments for metallurgical industries

Variable contents of nitrite (NO₂ ^?)- and nitrate (NO₃ ^?)-nitrogen are present in wastewater of metallurgical cylinder-producing industries after treatment in a physical-chemical plant. Biological denitrification and oxidation treatments to reduce the oxidized nitrogen forms to within legal limits were evaluated. Wastewater streams were characterized and quantified in order to build a pilot plant, improve strategies to reduce environmental impact and increase water recycling. Initial sedimentation of raw mixed streams reduced iron and zinc contents by 87% and 71%, respectively. The resulting COD was refractory to be used in biological phases and an added carbon source was necessary to optimise the denitrification process. The biological treatment gave good results even without subsequent physical-chemical treatments, lowering NO₂ ^? and NO₃ ^? values to below the 0.6 and 20 mg L^?1 limits respectively.     

Microalgae and wastewater treatment

Organic and inorganic substances which were released into the environment as a result of domestic, agricultural and industrial water activities lead to organic and inorganic pollution. The normal primary and secondary treatment processes of these wastewaters have been introduced in a growing number of places, in order to eliminate the easily settled materials and to oxidize the organic material present in wastewater. The final result is a clear, apparently clean effluent which is discharged into natural water bodies. This secondary effluent is, however, loaded with inorganic nitrogen and phosphorus and causes eutrophication and more long-term problems because of refractory organics and heavy metals that are discharged. Microalgae culture offers an interesting step for wastewater treatments, because they provide a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for several purposes. Microalgae cultures offer an elegant solution to tertiary and quandary treatments due to the ability of microalgae to use inorganic nitrogen and phosphorus for their growth. And also, for their capacity to remove heavy metals, as well as some toxic organic compounds, therefore, it does not lead to secondary pollution. In the current review we will highlight on the role of micro-algae in the treatment of wastewater.     

Biological treatment of saline wastewater in a rotating biodisc contactor by using halophilic organisms

Biological treatment of saline wastewater presents unique difficulties as a result of plasmolysis of microorganisms in the presence of salt. Removal of salt from wastewater before biological treatment by reverse osmosis or ion exchange operations are rather expensive. Inclusion of halophilic organisms in activated sludge culture seems to be a more practical approach in biological treatment of saline wastewater. A synthetic wastewater composed of diluted molasses, urea, KH₂PO₄, MgSO₄ and various concentrations of salt (0–5% NaCl) was treated in a rotating biodisc contactor (RBC). A salt tolerant organism Halobacter halobium was added onto activated sludge culture (50%) and used as inoculum. Effects of important process variables such as A/Q ratio, COD loading rate, feed COD concentration, salt concentration and liquid phase aeration on system performance were investigated. An empirical mathematical model describing the system's performance as a function of important process variables was developed and constants were determined by using the experimental data.     

Biological treatment of acid dyeing wastewater using a sequential anaerobic/aerobic reactor system

The treatment of the wastewater taken from a wool dyeing processing in a wool manufacturing plant was investigated using an anaerobic/aerobic sequential system. The process units consisted of an anaerobic UASB reactor and an aerobic CSTR reactor. Glucose, alkalinity and azo dyes were added to the raw acid dyeing wastewater in order to simulate the dye industry wastewater since the raw wastewater contained low levels of carbon, NaHCO₃ and color through anaerobic/aerobic sequential treatment. The UASB reactor gave COD and color removals of 51–84% and 81–96%, respectively, at a HRT of 17 h. The COD and color removal efficiencies of the UASB/CSTR sequential reactor system were 97–83% and 87–80%, respectively, at a hydraulic retention time (HRTs) of 3.3 days. The aromatic amines (TAA) formed in the anaerobic stage were effectively removed in the aerobic stage.     

Biological nitrate removal in industrial wastewater treatment: which electron donor we can choose

Biological denitrification was reviewed regarding its potential application to treating nitrate in industrial wastewater. Although heterotrophic denitrification is an efficient and well-developed process, some carbon content in wastewater is essential to maintain bacterial activity. Because of the high operating cost of heterotrophic denitrification caused by the required addition of a carbon source and potential “carbon breakthrough”, the study of autotrophic denitrification has attracted the interest of numerous researchers. Many advances in autotrophic processes have been made in the application of novel concepts and reaction schemes. While the main advantage of autotrophic bacteria rests on the reduction of operating costs by the replacement of an external carbon source with a cheaper electron donor, further decrease in cost requires additional refinement of these processes, including further improvement of reactor structure and optimization of reaction conditions. In the long term, new concepts are required for a compact wastewater treatment process. This review addresses the state of the art of each electron donor candidate for its potential application to the treatment of industrial wastewater containing nitrate.     

Biological treatment of 2,4-dichlorophenol containing synthetic wastewater using a rotating brush biofilm reactor

A newly developed rotating brush biofilm reactor was used for DCP, COD and toxicity removal from 2,4-dichlorophenol (DCP) containing synthetic wastewater at different feed COD, TCP concentrations and A/Q (biofilm surface area/feed flow rate) ratios. A Box-Wilson statistical experiment design was used by considering the feed DCP (50-500 mg l(-1)), COD (2000-6000 mg l(-1)) and A/Q ratio (73-293 m2 d m(-3)) as the independent variables while percent DCP, COD, and toxicity removals were the objective functions. The experimental data were correlated by a quadratic response function and the coefficients were determined by regression analysis. Percent DCP, COD and toxicity removals calculated from the response functions were in good agreement with the experimental data. DCP, COD and toxicity removals increased with increasing A/Q ratio and decreasing feed DCP concentrations. The optimum A/Q ratio resulting in the highest COD (90%), DCP (100%) and toxicity (100%) removals with the highest feed COD (6000 mg l(-1)) and DCP (500 mg l(-1)) contents was nearly 210 m2 d m(-3).     

Biological cyanide degradation in aerobic fluidized bed reactors: treatment of almond seed wastewater

The continuous aerobic transformation of synthetic cyanide waste-water, amygdalin solutions and almond seed extract containing cyanide was investigated in several fluidized bed reactors. Various inocula consisting of activated sludge or soil slurry were used. Successful inoculation was achieved with simple soil slurry. No significant influence was found between the performance of the systems inoculated with a cyanide contaminated soil and a garden soil. The performance and stability of the reactors with respect to degradation rate were tested for a range of cyanide loading conditions, with feed containing only cyanide, and with different additional carbon sources, as well as various CN ratios at a hydraulic retention time of 24 h. No growth with cyanide as the sole source of carbon and nitrogen was observed. The system with lactate as the organic C-source was capable of operating at cyanide concentrations of 160 ppm cyanide with a conversion rate of 0.125 kg cyanide/m³ d. Ammonia was the end product and the effluent concentration was 0.5 ppm CN^–. The systems with ethanol as the organic C-source could degrade only 0.05 kg cyanide/m³ d, whose feed concentration was 60 ppm cyanide. Amygdalin, an organic cyanide-containing compound present in stone fruit seeds, was fed as a model substrate. Degradation rates up to 1.2 kg COD/m³ d could be measured with no free or organically bound cyanide in the effluent. These rates were limited by oxygen transfer, owing to the large amount of degradable COD. The further investigations with almond seed extracts, confirmed the applicability of the aerobic process to treat food-processing waste streams having low concentrations of cyanide with high COD content.The authors with to thank Dr. Ö.M. Kurt for useful discussions.