D. Kozuharov

Characteristics of zebra mussel (Dreissena polymorpha) populations in infested reservoirs, northwest Bulgaria

The zebra mussel populations in the Reservoirs Ogosta and Rabisha (northwest Bulgaria, Danube River basin) were studied with respect to distribution, shell morphometry, abundance and biomass. In the reservoirs, the zebra mussels occurred at depths between 3.5 and 10.0 m and only on hard and mixed substratum. Based on principal component analysis, the majority of total variance of morphometric data was explained by the shell size and only a small proportion by the shell shape of the zebra mussels. In the Rabisha Reservoir, shell plasticity in respect to site location was observed. The absolute abundance and total biomass of zebra mussels differed among the sites within both reservoirs. The mean values in the Rabisha population were much higher than in the Ogosta population. The relations of shell morphometry, abundance and biomass of zebra mussels to the physicochemical conditions in the reservoirs were discussed.

The Zooplankton Composition in two Reservoirs in the North-West Bulgaria in Relation to Dreissena SPP. Occurrence

ABSTRACT The qualitative and quantitave parameters of the zooplankton in the reservoirs Ogosta and Poletkovtsi (North-West Bulgaria) were compared. The influence of the reservoir ecotone zones and the impact of Dreissena spp. distribution on the zooplankton composition were studied. Totally 75 zooplankton components were recorded in the reservoirs. The species Testudinella emarginula was newly recorded for the Rotifera fauna of Bulgaria. Most frequent and dominant components were copepodites and nauplii of Copepoda in both reservoirs, as well as copepods and cladocerans in the Ogosta and rotifers in the Poletkovtsi Reservoir. The zooplankton abundance and biomass in the Poletkovtsi were much higher than the Ogosta.

Structural/Functional Changes in Activated Sludge in PCP- and ONP-Biodegradation Technologies

ABSTRACT Different detoxication technologies (aerobic, anaerobic, two stage, hybrid) using oNP, PCP, DCP, TCP like model xenobiotics, have been accomplished in the last 8 years. The results about the details of the technologies have been described previously. In this paper the comparison between the efficiency of the different technologies and structural/functional changes of AS (activated sludge) has been made. The paper is illustrated by means of microscopic and transmission microscopic photographs. The results showed well expressed connection between the efficiency of xenobiotic elimination, type of technology, initial concentration of the particular xenobiotic and adaptive structure of AS. At aerobic shorter adaptation genus Pseudomonas played more important role in the detoxication. At time of the longer anaerobic and anoxic processes genus Acinetobacter assumed the govern role in the structure of xenobiotic-degrading bacterial complex. The deep knowledge of the adaptive structure of the different detoxication technologies presents the valuable information for quick and intelligent management of the detoxication bioremediation technologies.

Pentachlorophenol Biodegradation in Anaerobic and Aerobic Continuous Flow Processes

ABSTRACT Pentachlorophenol (PCP) biodegradation was studied comparatively in anaerobic and aerobic conditions. Two laboratory scale systems of completely mixed continuos flow bioreactor and secondary clarifier were used. Simultaneous treatment of municipal and industrial wastewater with high concentration of PCP (25 mg/l) was investigated. The results show that the biodegradation of trivial organic and PCP in aerobic conditions was better than in anaerobic conditions: the removal efficiencies were 83,3%(COD) and 55%(PCP) in the aerobic system against 41,3% (COD) and 47%(PCP) in the anaerobic system. The mean values of the effluent concentrations were 337 mg/l (COD) and 11 mg/l (PCP) for the aerobic experiment against 1263 mg/l (COD) and 12,8 mg/l (PCP) for the anaerobic experiment. Although the removal efficiencies of PCP and COD were relatively good for the investigated extremely high influent PCP concentration, both schemes did not meet the standards for the effluent concentration. Therefore the investigated bioreactors could be used only as a first stage in a system of bioreactors for completely PCP removal.

The Effect of Dreissena polymorpha on Bacterioplankton, Nematode Fauna and their Relations to Environmental Factors in Ogosta Reservoir (Danube Basin)

Abstract Spatial, seasonal, and annual bacterioplankton dynamics in recently infested by the species Dreissena polymorpha Ogosta Reservoir were studied for the first time during three year period. Bacterioplankton total number was higher in spring in ecotone zones, than in summer at thermocline. NH4-N, PO4-P, turbidity, dissolved oxygen, COD and chlorophyll-a correlate positively, while transparency and Ca2+ negatively with bacteria. Nematode species composition, included 22 species studied (13 rarely found and Rhabditis brevispina new for Bulgaria) belonging to nine families. The D. polymorpha impact is positive on nematodes and phytoplankton, negative on zooplankton and bacterioplankton, but weak positive on larger bacteria, rods and attached bacteria.

Dynamics of Dreissena spp. veliger larvae in some Bulgarian reservoirs

Two invasive mussels from the genus Dreissena occur in Bulgarian inland waters – Dreissena polymorpha and Dreissena rostriformis bugensis. They are well known invasive species, but there is lack of information about the presence, quantitative parameters and distribution of their larvae. We present the first data that concern the veliger larvae dynamics in Bulgarian inland waters, with several infested reservoirs being studied within the period 2009–2012. The present study was designed to determine their distribution, density and seasonal dynamics. Veliger larvae were found in all of the studied reservoirs. Their abundance was in the range from 166 individuals per cubic meter (ind m−3) to 28,400 ind m−3 in different seasons and reservoirs. The presence of veliger larvae was detected in the plankton also during the winter: February 2011 (3.7 °C) and March 2012 at temperature 7.5 °C. The maximum abundance of larvae was found at 26 °C. The variation among annual data, which was observed in our study implied that further regular and long-term studies of the early life stages of the Dreissena mussels is required in order to monitor the dynamics of these species in the inland waters of Bulgaria.

Bioindicative Potential of The Micro- and Metafauna in the Activated Sludge Towards ONP

ABSTRACT The bioindicative potential of the micro- and metafauna in the Activated Sludge (AS) towards shock load of oNP (ortho-nitrophenol) was investigated. Strong changes of the qualitative composition and quantitative parameters of the Rhizopodea Cilophora Flagellata and Rotifera in the model AS in the presence of 0.58 mmol oNP were registered. The experiment was carried out in two types of processes—continuous flow and batch system. At the start of the experiment qualitative and quantitative parameters of both systems were very high. At the end of the model processes the densities of all species were strongly reduced. The decrease of species density after oNP loading in the continuous bio-reactor was 53% and in the batch bioreactor was more then 80%. At the time of the earlier adaptation some of the organisms with shorter life cycle tried to adapt to the shock impact of the pollutant. The results showed that in case of immediately detected release of oNP to the plant pollution, a good decision is to isolate a part of the bioreactor and to set up batch regime there for the detoxification of the hazardous pollutants. The rest of the bioreactor can operate in continuos regime for removal of the trivial pollutants.

Biodiversity Response of Micro- and Metafauna in Activated Sludge Towards Toxic Effect of ONP and PCP

ABSTRACTThe complex of micro- arid metafauna in the activated sludge is a good and reliable indicator for quality of the waste water treatment process. The structural and functinal biodiversity response of this complex towards high toxic pollutants oNP (ortho-nitrophenol) and PCP (pentachlorphenol) in a model waste water treatment process in laboratory scale has been investigated. The obtained results confirmed the more important role of the macroorganisms in the indication and assessment of the bioremediation and relatively passive role of the micro- and metafauna towards the direct detoxication of the hazardous pollutants.