**3. Biotic index**

Aquatic insects of the freshwater river and stream ecosystems have frequently been examined to assess the species-habitat relationship concerning the water quality of the habitat [33]. Aquatic insects can indicate the water quality of streams, rivers, and lakes. Once aquatic insects are collected, and after analysis, the data can be compared between different sites by using four standard indices, i.e., Hilsenhoff's Biotic Index [34], EPT (Ephemeroptera, Plecopterans, and Trichopterans) Index [35], the Benthic Index of Biotic Integrity [25] and Beck's Biotic Index [36]. The EPT Index stands for Ephemeroptera, Plecopterans, and Trichopterans, three orders of Class Insecta which can easily be sorted, identified, and commonly used as water quality indicators. The EPT index is based upon a high-quality stream ecosystem with a great species richness. Biotic Index shows the quality of the environment by the presence of different organisms present in it, this index is also known as the "Family Biotic Index". This index is commonly used for river water quality. Biotic Index shows four basic water quality, i.e., (Excellent, Good, Fair, or Poor) measured as 1 to 10. 1 is good, and 10 is poor.

### **3.1 Biological monitoring working party-average score per taxon (BMWP-ASPT)**

Biological Monitoring Working Party-Average Score Per Taxon (BMWP-ASPT) is a biotic index method. That index also estimates the diversity of organisms concerning pollution level. According to different indexes, specimens are placed at various levels from 1-to 10. Plecoptera (rock fly larvae), Ephemeroptera (mayfly larvae), and Crustacea (pole shrimp) are on level 10, Gastropoda (freshwater limpet), Odonata (kini – kini) are at level 8, Trichoptera (caddisfly larvae) at level 7, Odonata (dragonfly larvae), Crustacea (freshwater shrimp) and Bivalvia (shell) at 6 levels, Hemiptera (backswimmer), Diptera (fly larvae), Trichoptera and Coleoptera (water scorpion, diving beetle) at 5, Arachnida (water mite) and Platyhelminthes (flatworm) at four levels, Syrphidae (rattail maggot), Hirudinea (leech), Gamaridae (water pig bug), Gastropoda (snail) and Bivalvia (shell) at 3, Chironomidae (mosquito larvae) at level 2 and Oligochaeta (worm) at level 1. The sequence starts from 10 as excellent and 1 as poorer. Many aquatic species are pollutants intolerant, i.e., levels 10–7 and absent in polluted water bodies. The greater the pollution, the lower the number of insects because few species are tolerant to pollutants, i.e., level 1. The BMWP score equals the sum of the tolerance score of all families in the sample. ASPT was calculated by taking the average number of the tolerance scores of all families of macroinvertebrates which varies from 0 to 10.

### **3.2 The HBI (Hilsenhoff biotic index) or family biotic index (FBI)**

The HBI (Hilsenhoff Biotic Index), also known as the family biotic index (FBI) calculates the level of tolerance in the community of a specific area and the categorization of each taxonomic group by relative abundance. Organisms are grouped with *Evaluation of Water Quality Using Physicochemical Parameters and Aquatic Insects Diversity DOI: http://dx.doi.org/10.5772/intechopen.108423*

a tolerance number 0–10, and 10 is the most tolerant, while 0 is the most sensitive to organic pollutants [1, 37–39]. The tolerance values were modified for macroinvertebrates for application in the Modified Family Biotic Index.

The family biotic index (FBI) is calculated as [37].

( ) ( ) <sup>∗</sup> FBI xi ti / n , = Σ

Where a *xi* is the number of individuals within a taxon, *ti* is the tolerance value of a taxon, and *n* is the total number of organisms in the sample. If the value is between 0.00–3.75, then excellent, 3.76–4.25 very good, 4.26–5.00 good, 5.01–5.75 fair, 5.76–6.50 fairly poor, 6.51–7.25 poor, and 7.26–10.00 very poor.

## **3.3 Ephemeroptera, Plecoptera, and Trichoptera (EPT) index**

EPT index was estimated by summing a total number of individuals group Ephemeroptera (Mayflies), Plecoptera (Stoneflies), and Trichoptera (Caddisflies). If the EPT number is greater than 7 per sample, then it is considered excellent, between 2 and 7 is good, and below 2 is considered poor [40].
